CORNELL UNIVERSITY LIBRARY QM 455.W67" """""^ """"^ Bran: Anatpmv, and Brain: Methods of rem 3 1924 024 791 505 <\ Cornell University Library The original of this book is in the Cornell University Library. There are no known copyright restrictions in the United States on the use of the text. http://www.archive.org/details/cu31924024791505 Bradford jnineral Brain. [Sprfngs. REFERENCE HANDBOOIi^OF TIjfe MEDICAL SCIENCES. ^ ^j^^- 10^^ of a persistent bitter taste. It is very insoluble in water (skVit). I'ut dissolves rather freely in alcohol, and more freely in chloroform. A second alkaloid, paraiii/ein, was found by Pa via to accompany the buxine in box ; and it is still probable that some other principle may be found to explain the poisonous qualities it has been occasionally observed to have. Uses. — Box has had some reputation as a febrifuge and tonic ; in large doses it is purgative and emetic. It is suspected of being sometimes used to replace hops in beer ; but it is little employed in medicine to-day. The alkaloid biixine (bebeerine), either from box or bibiru, has been offered as a substitute for quinine in intermit- tents, but Is much inferior; in the same large doses it deranges the stomach and digestion ; in small doses it, however, is an excellent tonic. Buxine has been found in several plants of entirely different orders, and is prob- ably, like berberine, a rather extensively distributed alkaloid. The bebeerine of bibiru (Nectandra Rhodim, Schomb.), the pelosine of pareira (Okondodendron tomen- tosum R. et P.), as well as of the false pareira, have been shown by Fliickiger and others to be identical with this alkaloid, although it is not quite certain that the physiological effects of buxine from all these sources are the same. The sulphate and hydrochlorate of buxine are in the market. Dose, as a tonic, from 5 to 10 cgm. (0.05-0. 10 = gr. i. ad ij.); as a febrifuge, eight or ten times as much (0.5-1 = gr. viii. ad xvi.). W. P. Bolles. BRADFORD MINERAL SPRINGS.— Merrimac County, N. H. Post-Officb. — East Washington, Hotel. Access. — From Boston viS the Lowell Railroad to East Washington ; thence one mile to hotel at springs. Stages await trains during the season from May 15th to October 15th. This spring became known to the white settlers in 1770, and since early in the present century its waters have chloride, sodium carbonate, calcium carbonate, magne- sivun carbonate, calcium phosphate, iron oxide, aluminum oxide, organic matter, sulphur, carbonic acid gas. We are unable from this analysis to assign the water to its proper class, although it is probably a sulphureted chalybeate. The spring yields twenty -one hundred gal- lons hourly. The water is clear and sparkling, and emits an odor of sulphureted hydrogen gas. It has been suc- cessfully used by the residents of the neighborhood in the treatment of certain cutaneous diseases, especially eczema. It is said to be a very efficient diuretic and tonic, and seems to be well adapted for rheumatism and diseases of the alimentary tract, and for conditions in- which the urine is scanty and. high-colored. As a douche in nasal catarrh and in catarrhal states of the vagina and uterus it has been found useful. There are bathing facilities for guests who wish to take hot or cold sulphur baths. The surroundings of the place are very attractive, and ample amusements and diversion are afforded the visitor in the way of bowling, shooting, fishing, driving, etc. James K. Crook. BRAIN. (ANATOMicAii.) — I. Introduction. § 1. Scope of this Article. — The development of the brain, its growth, histology, functions, blood-vessels and surgery, and the methods of its removal, etc. , are presented under appropriate titles. In this article the organ will be con- sidered mainly from the standpoint of normal morphol- ogy, with occasional elucidations from embryology, com- parative anatomy, and teratology. I regret that so many points remain undetermined and so many problems unsolved. These relate especially to the meninges and the olfactory region of the brain. § 3. Order of Treatment.— 1. Introduction, §§1-13. II. General Constitution of the Brain, Segments, etc., §§ 14-69. III. The Metencephal (postoblongata), §§ 70-90. IV. The Epencephal (preoblongata, cerebellum, and pons), §§ 91-128. supercentral 1. precentral t. superfrontal f medifrontal f. subfrontal f . aubf rontal g. presylTian 1. preoperculum orbital t. /l/teylvlan f . olfactory bulb meditemporal 1. postoblongata postcentral t. parietal f . paroccipital isthmus occipital f . paroc«ipital f . 4 exoccipital f . cerebellum myel Jig. 663.— Left Side ot tbe Brain o£ a Male Child at Birth; 478. X 1. The brain was mediseoted when Iresh, and the hemicerebrum spread and flattened considerably while hardening. The specimen is really the right hall, but for readier comparison with other specimens and figures a diagram was made (by Mrs. Gage) reversed so as to represent the left hall. This figure is based upon a photograph of the diagram. The cerebellum is correct in outline, but no details are shown. Other aspects of the same specimen are shown in llgs. 702, 756, 774, 775. Just ventrad of the narrow Isthmus, between the overlapping branches of the subfrontal and precentral fissures, is a white x ; 1, 2, 3, 4, 5, 6, undetermined fissures ; 7, an isthmus between 6 and the exoccipital which is nearly concealed by the adjoining gyres. See § 4. been used for medicinal purposes. An analysis by Dr. Jackson, of Boston, subsequently confirmed by Dr. Rich- ards, of Poughkeepsie, New York, showed the presence of the following ingredients: Sodium chloride, potassium V. The Mesencephal (gemina and crura), §§ 139-141. VI. The Diencephal (thalami), §§ 143-157. VII. The Prosencephal, its cavities, parietes, com- missures, fissures, and gyres, §§ 158-356. 136 REFERENCE HANDBOOK OF THE MEDICAL SCIENCES. Bradford JTIineral Brain. [Springs. VIII. The Rhinencephal (olfactory bulbs, etc ) ^§ :357-372. IX. The Meninges (dura, arachnoid, pia), §§ 373-409. X. Bibliography. g 3. Method.— li:h.B text consists largely of commen- taries upon the points illustrated by the figures. What seem to me the more important facts and fundamental ideas of encephalic morphology are embodied in concise propositions. Unless otherwise stated these propositions •apply to the human brain, and may not always hold good for those of other vertebrates, or even other members of the mammalian class.* § 4. Mg. 663 illustrates : A. The general aspect of a brain from the side ; its continuity with the myel (spinal ■cord) through the oblongata ; the existence of a smaller mass (the cerebellum) and a larger (the cerebrum) ; the overlapping of the former by the latter more extensive at birth, and in earlier tlian adult brains ; the existence of other parts, the olfactory bulb, the pons, and the oliva (the elliptical elevation of the postoblongata upon which the line from that word ends); the fissures of the cere- brum ; the subdivisions of the cerebellum (foliums) are not indicated. (The remaining points illustrated refer to the cerebral fissures, and may be considered more advantageously in ■connection with Part VII.) B. The simple, almost schematic, relations of the Assures demarcating the several operculums (compare Fig. 784) ; the preoperculum only is named. The sub- ■operculum is the region ventrad of the subsylvian fissure. The operculum is between the presylvian and Sylvian fissures ; and the postoperculum is the overlapping margin of the temporal lobe, the region on which is the word Syltian and ventrad of it. C. The incomplete covering of the insula (see Fig. 788) D. The presence of a distinct medifrontal fissure, sub- ■dividing the medifrontal gyre. E. The independence of the postcentral, parietal, and paroccipital fissures. F. The presence of the exoccipital (the " ape fissure " of some writers). G. The frequency of the zygal or H-shaped form of fissure — e.g:, paroccipital, parietal, postcentral, sub- frontal, orbital, and fissure S ; see § 307. § 5. The Facts. — Most of the statements are parts of •common anatomical knowledge, and special references are seldom given in this connection; therefore the fol- lowing extract from the preface to Huxley's "Anatomy of Vertebrated Animals " may be appropriately added : "The reader, while he is justly entitled to hold me re- sponsible for any errors he may detect, will do well to give me no credit for what may seem original, unless his knowledge is sufficient to render him a competent judge on that head." § 6. Tlie Ideas. — Unfortunately, the facts of anatomy are susceptible of various interpretations according to the relative weight assigned to them. In particular there are divergent views respecting the segmental con- •stitution of the entire brain and the normal pattern of the cerebral fissures. § 7. The Illustrations. — Of the one hundred and forty- Ave figures, one hundred represent preparations made iDy me for the museum of Cornell University ; these preparations are designated by their catalogue numbers. The drawings have been executed, from the specimens and from photographs, by Prof. E. C. Cleaves (C), Mrs. S. H. Gage (G. or S. P. G.), and Mrs. Wilder. The twenty-flve borrowed figures are credited to their sources. The remaining illustrations are original dia- grams or drawings, or direct reproductions of photo- graphs. § 8. Terminology.— The general subject will be dis- cussed in the article Terminology, Anatomical, in another volume ; meantime those interested are referred to the article under that title in Vol. VIII., of the first edi- * The uses of certain animal brains as aids In the study ol the hu- man organ are set forth in the article. Brain : Methods, etc., and in my paper, 1896, g. tion, pp. 515-537; to "Anatomical Technology " (Wilder and Gage, 1882) ; to the Reports, during the last ten years, of Committees of the American Association for the Ad- vancement of Science, the American Neurological Asso- ciation, the Association of American Anatomists, and the Anatoraische Gesellschaf t ; to the article, "Anatomical Nomenclature," by P. H. Gerfeh, in "Progressive Medi- cine," for 1899, pp. 337-346; to G. M. Gould's "Sugges- tions to Medical Writers," 1900, chap. iv. ; and to my address, "Some Misapprehensions as to the Simplified Nomenclature," Assn. Amer. Anat., Proceedings, 1898, pp. 15-39, and Science, April 31st, 1899. The principal publications prior to 1896 are included in the bibliography of my "Neural Terms, International and National," Jour. Comp. Neurology, December, 1896, vol. vi. Here, there- fore, it is necessary only to comment briefly upon the two groups of terms employed in this article. § 9. Terms of Position and Direction {Toponyms). — In place of the more or less ambiguous terms upper, lower, anterior, posterior, inner, outer, etc., will be employed terms referring to the regions of the vertebrate body in whatever attitude it may be — viz., dorsal, ventral, cepha- lic, caudal, mesal, lateral, ental, ectal, etc., constituting an intrinsic toponymy. The adverbial forms are dorsad, mesad, ectad, etc. § 10. Terms of Designation {flrganonyms) . — Each part is designated uniformly by one and the same name. Where two or more names are already in' use, the simpler or shorter has been chosen. In some cases simple names have been formed by the omission of unessential words or by the combination of two, or by the edinage of words from the Latin or Greek. Where the English form (paro- nym) differs froni the classical the former is often pre- ferred. For examples, " pneumogastric " becomes 'oa^us ; "pons Varolii," pons; "corpus callosum," callosum; "commissura anterior," precommissure ; "aquseductus Sylvii" and "iter a tertio ad quartum ventriculum" give place to mesocalia (the cavity of the mesencephal), Eng. mesocele.* § 11. Mg. 664 illustrates : A. The general form and appearance of the cerebrum of an educated and moral distinguished man, rapid in thought and movement. B. The general symmetry as to form and especially as to certain fissures, central, occipital, paroccipital, in- flected, associated withgome decidedly asymmetric con- ditions — e.g., the relations of the postcentrals to the para- centrals. C. The bifurcation of the dorsal end of both central fissures and the bifurcation of the caudal branch on each side. D. The coexistence of the more common relation of the paracentral to the postcentral on the right with the inclusion, on the left, of both branches of the postcentral within the curve of the paracentral ; see § 385 and Pig. 769. E. The great depth of both occipital fissures ; this is their real depth, and is not due to a superficial extension. F. The distinctness and simplicity of the paroccipital fissures, and the existence of the more usual combination — i.e., continuity with the parietal on the left and inde- pendence on the right; see Fig. 778. G. Nevertheless, the difiiculty of deciding how this case should be entered upon a 'Table. On the right the isthmus between the parietal and the paroccipital is per- fectly distinct and visible in any direct view ; yet it is below the level of the adjacent gyres and might perhaps be regarded as a vadum. On the left the vadum (at the point marked 13) is mu6h more depressed, and hidden from easy view by the overlapping gyre just cephalad of it. H. The unusual complexity of the fissures represent- ing the parietal and the postcentral. On each side there are recognizable three irregular fissures caudad of the central ; the most dorsal of each group is triradiate and * Orthographic discrepancies between this article and my recent papers (e.g., in the retention of certain diphthongs and of the ultima of anatomical, morpholngieal, etc.) are due to the necessity of con- forming to the plan of the entire worki 137 Brain. Brain, REFERENCE HANDBOOK OF THE MEDICAL SCIENCES. perfectly distinct, and is marked postcentral; on the right one of the rays (4) cuts the margin of the hemi- cerebrum deeply. The most ventral (2 and 9) joins the superfrontal (?) inflected (?) 8 superfrontal (?) inflected (?) parocclpital occipital paroccipltal occipital Fig. 664.— Dorgum of the Cerebrum of James Edward Oliver, Professor of Mathematics in Cornell University ; aged sixty-six ; 3,334. X .57. When removed the hrain was firm in texture and weighed (with the piaiachnoid but without the dura) 1,416 gm. (49.94 ounces), approximately 50 ounces. It was transected at the mesencephal; the cerebrum was medisected and each half hardened while resting in a mixture of alcohol, formal, zinc chloride and water, of specific gravity equal to that of the brain ; later it was transferred to Increasing strengths of alcohol. The cere- brum is believed to retain very nearly its natural form. The diacele ("third ventricle") was unusually wide and the medlcommissure wholly absent (see § 152) . There were no obvious signs of diseased conditions beyond a slight opacity of the piarachnoid about the dorsal ends of both central fissures. Professor Oliver was a man of the purest character and a pMlosophlc thinker, in not only the higher mathematics, but other sciences and ethics. He was left-handed and absent-minded, but rapid in thought and action. For an account of his life and a list of his writings, see the memoir by G . W. Hill, read before the National Academy of Sciences, April, 1896 ; also Science, April, 1895, and the Ithaca Journal, March 28th, 1895. 1 (right) and 8 (left), fissures parallel with the centrals and representing, perhaps, both precentrals and supercentrals : they unite with the longitudinal fissures (superfrontals ?) ; but a vadum exists on each side ; 2 (right) and 9 (left), the most ventral of the postcentral groups ; 3 and 10, the middle of ea«h group (sub- central ?) ; 4, a ray of the postcentral cutting the margin of the precuneus ; 5, the right paroc- clpital isthmus ; 6, an incision ; 7, a distinct diagonal fissure ; 8, see 1 ; 9, see 2 ; 10, see 3 : 12, a fissure cutting the margin of the precuneus deeply but connected with neither the paracentral nor the postcentral ; 13, location of the paroccipltal vadum. Inadvertently no guide lines indicate the parietal fissures, but they mfiy be recognized from their relations to the paroocipltals. See § 11. Sylvian Assure. The middle one (3 and 10) is continuous with the parietal on the right, hut on the left a vadum may be recognized. I. The unusual location, depth, and symmetry of the inflected (?) fissures. § 13. Beferences. — In the Bibliography at the close of this article the names of authors and editors are arranged alphabetically. The date after the name is the year of publication, and the following letter, if there is one, designates a particular paper or book out of two or more published within a single year. My own name is abbre- viated in the text to W. My papers on the structure and nomenclature of the brain prior to 1897 are enumerated in the Bibliography of "Neural* Terms," 1896, h, which is probably accessible to most anatomists either as a reprint or in the Journal of Oonvparatim Neurology. § 13. Acknowledgments. — For assistance in the making of preparations or photographs, for suggestions as to methods, for helpful criticism of the former edition, or for the loan of figures, I am indebted to the following former students, of whom several are present colleagues : P. A. Fish, S. H. Gage, Mrs. Gage, G. S. Hopkins, O. D. Humphrey, B. F. Kingsbury, W. C. Krauss, B. D. Myers, and B. B. Stroud. II. General Constitution op the Bhain. § 14. Definition. — The brain (Gr., iyKii^akog; Lat., cereln-um; lateLat., encepTialon; It., ceriiello, eereibro ; Sp., eerebiv ; Fr., cerwau; Ger., Oehirn ; Eng., encephalon, eneephal) is the enlarged, segmented, ce- phalic ("anterior") portion of the neuron or cerebro-spinal axis. § 15. The neuron* is that one of the great mesal (me- dian) organs which is nearest the dorsal surface of the body, and farthest from the heart (Fig. 665). The other two are the enteron (alimentary canal), and the axon (skeletal or body axis; notochord in early em- bryos, but in later stages and adults the series of centrums or bodies of the vertebrae), Fig. 670, odontoid process, etc. The enteron is in the ventral (he- mal) cavity; the neuron oc- cupies the dorsal (neural or cerebro-spinal) cavity; the ax- on forms a partition between the two. § 16. Mg. 665 illustrates : A. The existence, in man as in other vertebrates, of two par- allel body cavities, a dorsal or neural, and a ventral or hemal, separated by the axon, the skeletal axis. B. The presence, in the ven- tral cavity, of the 'heart, a hol- low muscular organ, rhythmi- cally contractile during life. 0. The presence, in the ven- tral cavity, of a muscular tube, the enteron (alimentary canal). D. The presence, in the dor- sal cavity, of a subcylindrical rod, the nsuron (cerebro-spinal axis), itself containing a cav- ity, the neurocele ("central canal " and " ventricles "). § 17. Excepting at its first formation (when it is a rod with a dorsal furrow) the en- tire neuron is a tube, a sub- cylindrical mass enclosing a cavity. This cavity is the neurocele, and the enclosing material constitutes the celian parietes. The existence of the neurocele may be demonstrated by the transection * Certain points relating to this word will be discussed in the article Te/rmimology, Anatomical. The following brief statement is the ab- stract of my paper, 1899, d, as printed in Science, March 18th, 1900, 420 : "Is neuron available as a de^naUon of the central nervous sustem ? Neuron (from to i/eCpov) was proposed by me in this sense . in 1884 (JV. T. Med. Journ., August 2d, p. 114), and employed in the same Journal, March 28th, 1^ p. 356 ; in addresses before the Amer. Neurol. Assn. (Jovm. Nerv. and Ment. Dis., July, 1885) ; Amer. Assn. Adv. Sol. Proceeding, 1885, and in the second edition of ' Anatomical Technology,' 1886. It has been employed by McOlure, Minot, Waters, and others. The reasons for its abandonment in 1889 for neuraxis, as stated in the Proceedings of the Assn. Amer. Anat- omists for 1895, p. 44, and Ref. Handbook of Med. Sci., ix., 100, now seem to me Inadequate. Newon is the basis of neural (as ap- plied to aspect, folds, furrow, and canal) and of ncurenteric and other compounds, and it is the natural correlative of enteron (entire alimentary canal) and of axon (notochord or primitive skeletal axis) . Not until 1891 did WaJdeyer propose newon for the nerve cell and its processes; not until 1893 did Shafer apply it to the axis-cylinder process. As with tardus and cUium, the context would commonly avert confusion between the macroscopic and microscopic signlflcar tlons of the word in a given case. The compounds macronewon and micnmeuron might be employed if necessary, or (as suggested by Barker, 1899, p. 40), the histologic element might be designated by neurone, as if from vtvpiiv. The question is now further complicated by Van Gehuchten's adoption of Newr&ce as the title of a new jour- nal of neurology." 1 138 REFERENCE HANDBOOK OF THE MEDICAL SCIENCES. Brain. Brain. of any part of the neuron in any other vertebrate, and in an immature human being; but ■with the adult, in certain regions, the olfactory bulbs (Fig. 672) and most of the myel (spinal cord, Fig. 670), the cavity is more or less completely obliterated. § 18. Location. — The brain is contained mainly within the cranium, although part of the postoblongata or even, neuraxls esopbagus I neurocele aorta | 2 ^ Fig. 665.— Caudal Aspect of a Thoracic Transection of a Fetus About 3.9 cm. from Nates to Bregma, and Estimated at Ten Weeks ; 2,139. X i. 1, Thorax, part of the ventral or hemal cavity ; 2, spinal canaL part of the dorsal or neural cavity ; 3, scapula. Defects. — The fetus was badly shrunken by immersion In too strong alcohol, and the parts here shown dried somewhat while photographing. Certain details as to the pleura, spinal nerves, and arachnoid are omitted, the object of the figure being mainly dia^ grammatic. gee § 16. as appears in Fig. 670, a little of the cerebellum, may ex- tend beyond the limits of the foramen magnum. It is remarkably sheltered and clothed by the cranial bones and by the soft parts ectad and entad of them, the scalp and the meninges (dura, arachnoid, and pia) (Figs. 795, 796, 798). § 19. The Brain a Modified Tube. — In its simplest ex- pression the brain, like the remainder of the neuron, may be represented as a tube of nervous tissue lined by a non- vascular, ciliated* epithelium, theendyma("ependyma"), and covered by a vascular membrane, the pia ("pia mater "). § 20. In what may be regarded as an approximately typical condition, the paiietes consist of three layers or strata, viz., an ental, mainly cellular, adjoining the endyma, the entocinerea ("central tubular gray"); an '«ptal, mainly cellular, adjoining the pia, the eetocinerea (cortex) ; an intermediate, fibrous, between the other two, the alba or medulla; see Fig. 666. In some regions, particularly the epicelian and paracelian roofs, the ento- cinerea is dislocated or crowded as it were from its nor- mal position next the endyma by albal or fibrous intru- sions, commissures, especially the callosum. Parts of the eetocinerea (e.g., claustrum and lenticula. Fig. 781) are also separated more or less completely from the rest. § 31. UnegualThicknessof the Parietes.— In the earliest * There is considerable divergence of statement among authors as to the presence of cilia, especially in adults. P. A. Fish has described (1890, 256) the ciliated ceUs in the encephalic cavities of the cat, both old and young. He urges the Importance of thorough preservation by the injection of the preservative into the cavlUes ; states that a magnifi- cation of not less than six hundred diameters must be employed, and intimates that the failure to recognize them in man may be due to de- fective methods of preparation or examination. See also the recent paper of StudniSka : ' Ueber das Ependym des Centralnervensystems Wlrbeltiere," Sitzungsber. K. BOhm. 6es. Wim., Math. Nat. CI., 1899, xlv., p. 7. stages the celian parietes are of approximately equal thickness throughout, although certain portions of the roof, e.g., of the metacele, are never so thick as portions of the fioor. With some low or generalized vertebrates — e.g., Seymnus, a shark (T. J. Parker); Necturus, a sala- mander (W., 1884, a, Fig. 16); Ceratodm, a Dipnoan (W., 1887, a)— this condition prevails throughout life, at least with certain regions. With man, until the fetus attains a length of at least 6 cm., and an estimated age of twelve weeks (see Fig. 667), the cerebral parietes are almost uniformly thin; when 24 cm. long, and about twenty weeks old, certain regions are considerably thicker than others, as seen in Fig. 716 ; in the adult brain of man, and indeed of mammals gen- erally (Figs. 686 and 735), the difference between even closely adjacent portions of the parietes is simply enor- mous; compare, e.g., the mesencephalic floor (crura) with the caudal part of its roof, valvula (Figs. 670 and 687) ; the two divisions of the epicelian roof, cerebellum and lingula (Figs.- 670, 687, 703) ; the diacelian sides, thalami, with the floor, tuber or terma (Figs. 670 and 687) ; the thin or membranous parts (fimbria, tenia, pala, etc.) adjoin- ing the rima with the ad j oining hippocamp and caudatum (Figs. 716 and 732). § 33. Tdas. — Where the proper nervous constituent of the parietes is .wanting ' the endyma and the pia are in contact and constitute a membranous area or zone, a tela. Among vertebrates the most constant and extensive of these is the roof of the metacele, the caudal portion of the " fourth ventricle, " here called metatela (Figs. 675, 680, 686). A similar portion of the roof of the "third ventricle" is the diatela (Figs. 675, 681, 683) ; its cephalic continua- tion as the roof of the aula is the autatela; finally, in man and apes, a part of the floor of the paracele (" lat- eral ventricle ") is a membranous zone, the paratela (Figs. 783, 785). § 33. Fig. 667 illustrates : A.— The large size of the paracele, the thinness of the parietes and their nearly uniform thickness. B. The extent of the paraplexus, and its fulness as compared with that in the adult. Possibly when fresh it end yj ^ ''^^T:a^' f^^ Fig. 666.— Schematic Transection of the Brain, representing the topographical relations of the two kinds of nervous substance, the white, which is fibrous and conducting, and the gray, which is cel- lular as well as flbrouff,"SBid dynamic In function. The entocinerea Is primary, and alone exists In the myel : the eetocinerea is second- ary ; It constitutes the mesencephaUo cappa, and the cortex of the cerebrum and cerebellum. The olUa are omitted. more nearly filled the paracele, but was contracted by the alcohol (compare Figs. 716 and 735). C. The similarity of the precomu and medicomu. D. The absence of distinct indication of the postcomu, indicating that this may be formed eventually not by a special protrusion caudad, but by the thickening of the 139 Brain. Brain, REFERENCE HANDBOOK OF THE MEDICAL SCIENCES. parietes in such a waj' as to leave an occipital space of variable size. E. The commencing formation of the hippocamp as a corrugation of the mesal wall of the medicornu. paraplexua. Sylvian f oBsa llippocainp (Fig. 667.— The Left Hemicerebrum of a Fetus (Measuring 6 cm. from Bregma to Heel, and Estimated at Twelve Weeks), Opened from the Lateral Aspect; 340. X 3. 1, A Assure; 2, tip of temporal lohe. F. The non-extension of the paraplexus and thus of the rima to the extremity of the medicornu. G. The presence of at least one distinct transitory fis- sure (1). H. The evidences of some mesal fissures as slight corrugations just cephalad of the plexus. I. The formation of the Sylvian fossa, with as yet no trace of the insula. § 34. Plexuses. — As already stated the endyma is non- vascular ; but provision is made for the practical intro- duction of blood-vessels into the encephalic cavities by ■ fornix portiplexus thalamus Tig. 668.— Schematic Representations of Four Stages in the Formation of the Portiplexus, as a Type of Plexuses. At A the porta is seen to have the following boundaries : cephalad, the fornix ; caudad, the thalamus : ventrad, the junction of the two ; dorsad, however, there Is merely the endyma passing from fornix to thalamus, and the ectal pial fold, one of its laminae being f omlcal and the other thal- amic. The flrst step in the formation of any entoceUan plexus is represented at B, where the plal fold (or vessels therefrom) pushes the endyma before it into the cavity. At C the process Is carried a step farther, and at D the parts are represented as in the adult, with the plexus apparently Inside the porta, and yet really excluded from the cavity hy the unbroken covering of endyma. the formation of plexuses at various points. A plexus is an apparent intrusion of a fold of pia, or of vessels from the pia, into one of the cavities ; but the endyma is carried before the intruded portion, and covers it com- pletely so that, strictly speaking, neither the pia nor its vessels are in the cavity. The conditions are comparable mesocele-^ epicele^ lateral recess . cerebellum . eplplexus. preoblongata with the relations of the abdominal viscera to the peri- toneum. If one takes a closed sack of flexible material and pushes the fist against one side it may be carried so far as apparently to be within the sack; yet all the while it is covered by the material of the sack and strictly excluded from the true cavity. Simple examples of the ' plexus formation are presented by the epiplexus (Fig. 695), and portiplexus (Fig. 668). The metaplexus is seen in Fig. 686; the diaplexus in Figs. 686 and 733; and the paraplexus in Figs. 718, 736, and 733. The dispropor- tionate size of the paraplexus at early stages (Figs. 667 and 747) indicates that it is intimately related to the growth of the cerebrum. The structure and diseases of the paraplexuses are discussed by Findlay, 1889. § 35. Bipa. — "Where the endyma leaves the nervous parietes either at the margin of a tela or for reflexion upon a plexus, there is a sort of shore line which I have called ripai The name was originally given to the ragged edge left when a tela or plexus is torn from the nervous parietes (see Figs. 693, 699). § 36. Mg. 669 illustrates : A. The effect of the cranial flexure (§ 36), the two segments, mesencephal and epen- cephal, with their cavities, appear- ing upon the same section surface. B. The triplic- ity of the epicele, consisting as it does of a mesal portion and two lateral extensions, the lateral recesses (§60). In Fig. 695 the lower part of the figure is still more enlarged, and commented upon. 8 97 T J« Tlfnin FIG. 669.— Transection of the Brain of an Em- §,«/. ineisrain bryo Rabbit, Slxtfeen Days Old. X 9. (From as a Bouse. — KOlUker.) Within certain limits the brain may be likened to an edifice, and the comparison has been carried out in some detail on p. 413 of Wilder and Grage, 1883. Architectural terms, floor, roof, sides, may be employed appropriately to in- dicate the general locations of the parts relatively to each other and to the common cavity, and I have proposed two specific terms, aula (a hall) and porta (a doorway), for the designation of certain portions of the cavity. § 38. Irregularities of Contour. — In the brain straight lines and plane surfaces are infrequent, and the spiral form is not uncommon ; hence dissections are often more instructive than mechanical sections, and normalization, actual or ideal (§ 38), is sometimes desirable. § 39. Commissures, etc. — Of the parts connecting lateral masses across the meson, whether cellular or fibrous, whether direct (true commissures) or oblique (decussa- tions), some are merely specializations of pre-existing floors or roofs; e.g., precommissure, postcommissure, supracommissure, pons ; others, the callosum and com- missure of the fornix, are marked extensions of pre- existing lines or areas of conjunction (Fig. 741). The medicommissure, finally, as well remarked by Spitzka, is rather a fusion of contiguous surfaces than a com- missure in the usual sense of the word. § 30. Atrophic Parts. — Certain parts (terma, hemi- septum, valvula, tuber) which are very thin and ajj- isarently functionless, nevertheless serve to contain the neurolymph (cerebrospinal liquid), and may have a morphological significance as representing parts more developed in other forms. Two other parts, the epiphy- sis ("pineal body") and the hypophysis ("pituitary body ") are rather thick than thin, but are not known to have definite functions ; their peculiarities will be con- sidered in connection with the diencephal (§§^i46, 154), of which they are appendages. § 31. Bipa/rian Parts.— Along the ripas, or hnes ot re- 140 REFERENCE HANDBOOK OF THE MEDICAL SCIENCES. Brain.. Brain.. flection of the endyma upon telas or plexuses, the sub- stantial nervous parietes are commonly reduced iij thick- ness, so as to resemble the terma, valvula, and tuber in some degrea Such are the obex at the end of the metacele (Pig. 702) ; the fimbria along the hippocampal margin of the rima, the tenia along its caudatal margin, and the pala at its extremity (Figs. 730, 732, and 735). 32. The riparian condition may not be incompatible longituajnal sinus todJcafes the location of the dorsal end of the central Assure ; 2, caudal part of the paracentral Assure ; 3, inflected Assure ; 1 *2£^^J?^™*' Assure ; 5, callosal margin of the falx, indicated hy the interrupted line ; 6, occipital Assure ; 7, calearine Assure : 8, in the 'o^Kitudin^ sinus just dorsad of the torcular ; 9, tentorial sinus ; 10, a sphenoidal sinus (not vascular, but a cavity in the sphenoid hone) ; II, a trontai sinus ; 12, naso-palatine canal ; 13, basioccipital hone ; the basisphenoid has 10 upon it, but the two bones are continuous : U, naso-pharynx ; IB, oro-pharynx ; 16, soft palate. The heavy black line bounding the shaded mesal cavities is the endyma. IJejects. The planes of section of the brain and of the other parts are not absolutely identical, although perhaps nearly enough so for most purposes. Many of the boundaiy lines are too faintly indicated, e.g., that of the section of the chiasma. A continuous line represent- ing the pia should have surrounded all the out surfaces in close contact therevpith. Another line representing the arachnoid should follow the general contours, as stated more fully in connection with Hg. 801. The segmental name dUncephal, hides most of the oval area indicat- ing the medicommissure ; this laat should have been named and should not be dotted. The heavy black line representing the endyma should 5?ir?,»T ?^ i * stemdnfundibulum) of the hypophysis, and into the epiphysis, as in Fig. 687. At the second e of the abbreviation MBSEN the endymaj line should not be Interrupted. The interruption opposite the n of the abbreviation METEN represents the metapore (foramen of Maeenale), and should have been so ck ignated as in Eig. 687. Notwithstanding the minuteness of the myelocele ("central canal of the cord ) In the human adult its location », lonld have been Indicated by the continuation of the endymal line. The neck, scalp, features, and all the soft, vascular parts are swollen i y the aUnJection; the margins of the tongue are moulded upon the teeth; the soft palate and dorsal wall of the pharynx are obviously thickened, and the subturblnal projects beyond the true margin of the septum into the naso^jharynx, as is perhaps the ease temporarily during the congestion attending a severe " cold in the head." No attempt has been made to indicate the blood-vessels, the structure of the skin, the exact direction of the lingual muscles, or the details of the nuchal region. 141 Brain, Brain. REFERENCE HANDBOOK OP THE MEDICAL SCIENCES. metatela ■ ■with distinct and even important functions. The supra- commissure and the habena (Fig. 707), for example, are, in one sense, pai'ts of transition from substantial to mem- branous parietes; but they doubtless, like the fimbria, have some distinct use. § 33. Marginal Cinerea. — The riparian parts mentioned in § 31 consist of alba; but with the cerebrum and cere- bellum the cortical margins have a special morphological interest, and are but little known. § 34. Physiologically the intermediate portions of organs are commonly most important, as well as most easily recognized and examined; but morphologically the extremes have great significance, and present un- solved problems for future investigators. § 35. Fig. 670 illustrates : A. The relative location and extent of the cranial and facial regions of the head so far as they appear at the meson. B. The continuity of the two portions of the neuron, the myel (" spinal cord "), and the brain (encephal), at or near the junction of the cranium with the spine. C. The obvious subdivision of the brain into several regions, represented, for example, by the cerebellum, the cerebrum, and the intervening narrower part, which is sometimes called isthmus cerelyri. D. The possibility of recognizing in the adult brain smaller divisions or definitive segments, corresponding with the divisions of more nearly equal size in certain other vertebrates. E. The difficulty of assigning exact lim- its to the brain and myel or to the regions of the brain, since they are continuous and do not present arthra (articulations or joints) as with the skeletal segments. F. The representation of each segment at or near the meson by some well-known part: the metencephal by the postoblon- gata; the epencephal by the cerebellum and pons ; the mesencephal by the crura and geminal lobes ; the diencephal by the thalami; the prosencephal by the cere- brum ; and the rhinencephal by the olfac- tory bulbs. G. The existence of a mesal series of communicating cavities surrounded by the endj'ma. H. The insignificance of the aula, the mesal cavity of the prosencephal, as com- pared with not only the other cavities but the cerebrum itself. I. The presence of an orifice, the porta ("foramen of Monro"), evidently leading laterad from the mesal aula into a cavity within the right hemicerebrum. J. The relations of the masses to the cav- ities, as are related the floors, roofs, and side walls of an edifice to the apartments. K. The great difference in the thickness of the roofs and floors at diilerent points. L. The continuity of the side walls, floors, and (ex- cepting at one point) of the roofs. M. The existence of certain fibrous masses, commis- sures, extending across the meson, and therefore divided in this preparation. N. The lodgment of a subspherical appendage of the base of the brain (the hypophysis) in a deep pit in the fioor of the cranium (the "pituitary" or hypophysial fossa). O. The change in direction of the cranial floor at about this point, the remnant of the embryonic cranial flexure. P. The similar angle formed by the base of the brain. Q. The still more decided angle formed by the general outlines of the floors of the encephalic cavities at a point nearly corresponding with the cephalic orifice of the mesencephalic cavity. R. The liability of misapprehension from the employ- ment of the ordinary descriptive terms, vertical, Iwri- zontal, antmor, posterior, upper, and lower, since each of these words would have one meaning for the myel and postoblongata, and another for the diencephal. It is as if two adjoining houses faced, one to the east and the other to the south. The employment of eastei-n and south- ern as designating structural features common to the two would be likely to cause misapprehension. S. The convenience of regarding the entire floor as ventral, the entire roof as dorsal, any region of the brain nearer the myel as relatively caudal, and any region farther therefrom as relatively cephalic. T. The dorsal expansion of most of the segments. The wedge-like shape of the mesencephal is easily recog- nized ; the thalami are not wholly exposed, but the region is more extended dorsally than ventrally ; the cerebellum is much larger than the pons, while the disproportion of the cerebral hemispheres to their strictly basal, mesal part, the aula, is one of the many remarkable features of the adult human brain. U. The tendency of certain segments to overlap ad- joining parts, especially in the caudal direction. V. The lack of exact collocation between the en- cephalic regions and the cranial bones ; the cerebellum corresponds to less than half of the superocoipital bone, and extends a little beyond its margin at the foramen magnum. "istbmus cepbalic neck. epiphysis optic nerve eye Fig. 671.-RlgM Side of the Brain of an Embryo 23 mm. Long and Estimated at Elgbt Weeks; 2,652. X 7. Prepared and drawn by B. B. Stroud (1899, o) . 1, Cranial flexure ; 2, torn edge of tbe metatela ; 3, pons flexure. Tbe olfactory bulbs are not shown. See S 37. W. The collocation of the lambdoidal suture with the dorsal end of the occipital fissure. X. The location of the mesal craniometric points, nasion, bregma, lambda, and inion. § 36. The Encephalic Flexures. — These are commonly described as three, the cranial, the pons, and the neek. The second and third are temporary in man, respectively indicating the junction of the myel with the postoblon- gata and of the latter with the preoblongata. The cranial or mesencephalic fiexure is a permanent feature of the human brain, as seen in Figs. 670 and 687. There is, in addition, a flexure, likewise pei-manent, in the diencephal so that the prosencephal is dorsad instead of cephalad of it ; this persists in man and other Mammals, and in Birds and Reptiles, but with Amphibia and "fishes" the pro- socele and diacele are on approximately the same level ; see my papers, 1887, 6, and 1896, d. The rela tive positions of the several encephalic flexures, although^ot their relative sharpness or the length ol tne intervening parts of the brain, may be indicated to tne 142 REFERENCE HANDBOOK OF THE MEDICAL SCIENCES. Brain. Bralu. eye approximately by a capital W, with an oblique line In the accompanying diagram (half of a V) for the myel. the three flexures commonly named are Pr. Cranial Neck indicated by the words cranial, pons, and neck ; Pr. stands for the prosencephal- ic region, and D. for the diencephalic flex- ure. In this diagram, D. Pons Myel in accordance with my custom, the cephalic (" anterior ") end is at the left. Unfortunately, however, the two figures which illus- \AA callosum (genu) terma — precribnim —J- optic nerve — I cMasma optic tract lura tuber albicans postcribrumj pregenloulum D. The presence of corrugations on both the mesen- cephal and the cerebrum. The former appear in many of our preparations ; the latter may be artifacts. § 38. Normalization. — This term is used toinclude all processes by which modified or morphologically ab- normal f6rms and relations may be reduced, either ac- tually or ideally, to their known primitive and presumed normal conditions. Beetification would have nearly the same significance ; it denotes the reduction of complex structures to simple, of irregular to regular, of crooked to straight, and of rough to plain. Examples of this process are the representation of the segments as subequal in size and on the same plane (Figs. 674 and 675) ; the lateral extension of the various outgrowths of the mesal ■ olfactory f . - olfactory bulb -olfactory cms peduncular sulcus p istoblongata vallis Fig. 672.— Base (Ventral Aspect) of the Brain. From Henle, Edinger, and nature. X .7. 1, Ventral ("anterior") column; 8, line between the ventral and lateral column ; 3, veutrimesal Assure. Prcpa/raUon.— The cerebellum has been allowed to fall dorsad by its own weight ; thereby the occipital lobes are divaricated somewhat, the encephalic curvature is reduced, and the crura are more fully exposed. The hypophysis and inf undibulum have been severed from the tuber, and the pia removed, together with the cranial nerve roots, excepting the optic. The right olfactory crus has been divided near Its attachment. On the left the operculums are divaricated somewhat, so as to expose the ventro-lateral aspect of the insula. Defects.— As may be seen from proflle views of the brain (Figs. 670 and 687), in the normal condition of the organ the pons and the ohiasma are naturally nearly in contact, and the intervening regions, crura, etc., are practically Invisible ; the ventral surface of the met^ epencephal also forms little more than a right angle with that of the prosodiencephal; consequently in a direct view of either region the other is greatly foreshortened, and even the equal division of the obliquity between them shows neither to advantage. The fresh or imperfectly preserved brain, when resting upon the dorsal aspect, will, however, straighten itself, as it is commonly represented. To include so large a surface within a figure of moderate size certain details must be Inadequately presented or omitted altogether. The Assures in the present figure, substantially as given by Henle, need not be regarded as signifying anything more than the general aspect of the cerebrum. The two crura should be equal in width. The pyramid decussation is inadequately Indicated (see Fig. 689) . See i 41. trate the flexures most perfectly (671 and 676) have the reversed position, so that comparison with the diagram is less readily made. § 37. Fig. 671 illustrates : A. The general form of the brain at this stage, especially the sharpness of the several flexures. B. The size and prominence of the mesencephal and its extension over the adjoining regions. C. The distinctness of the constriction cephalad of the mesencephal as compared with that oaudad, and the apparent absence of reason why the latter should be re- garded as a definitive segment anymore than the former. parts (Figs. 688 and 714) ; the straightening of the medi- cornu (Fig. 739); the schematic representation of the fissures (Figs. 757 and 758), and the designation of the human geniculums as pre and post rather than external and internal (§ 63, K). § 39. TM Brain a Segmented Organ. — A fundamental morphological idea * of the brain is that it consists of a series of segments, comparable, although not, probably, * Like other symmetrical organs it consists of right and left halves, approximately identical. It is also regarded by some as divisible into dorsal and ventral zones ; but this has not, I think, been demonstrated for the entire brain. 143 Brain, Brain. REFERENCE HANDBOOK OF THE MEDICAL SCIENCES. strictly equivalent. The development and comparative anatomy of the organ can hardly be treated upon any other basis; it is recognized in the discussion of en- cephalic physiology and of psychology, and the descrip- tive anatomy of the organ is most conveniently based thereon. § 40. The segmental constitution of the human brain is Invisible from the dorsal aspect (Fig. 664) ; hardly sug- gested when the cerebellum as well as the cerebrum is in view ; more obvious from the lateral aspect (Fig. 663) ; still more so from the ventral side (Fig. 673) ; clearer still from the mesal aspect (Figs. 670, 687, and 756), and unmis- takable with early embryos (Pigs. 671, 673, and 679), which therefore, but for practical dilHculties as to procur- ing, preserving, and dissecting, would form a natural introduction to human encephalic morphology. § 41. Mg. 672 illvMrates : A. The enonnous prepon- derance of the visible parts of the prosencephal and epen- cephal over the other segments, thereby occasioning the common and not unnatural though very unphilosophical division of the entire brain into cerebrum (cerebrum proper, olfactory bulbs, and thalami) and cerebellum (with pons and postoblongata), the intervening, narrow region, the craraand the quadrigeminum, being regarded as merely an isthmus.* From the morphological stand- point, however, the statement would be nearly reversed. The mesencephal is at one period the most prominent and distinct region (Figs. 671 and 676). The cerebellum may be characterized as an hypertrophied bridge over the "fourth ventricle," and there are some grounds for re- garding the olfactory bulbs as PROSENCEPHAL ._.. cerebrum MESENCEPHAL gemina EPENCEPHAL '■ .cerebellum METENOEPHAL postoblongata MYEL RHINENCEPHAL Olfactory-bulb DIENCEPHAL tbalami [.concealed'} FIG. 673.— Fetus Measur- ing 49 mm. from Nates primary, and the cer- ebral hemispheres as their secondary ap- pendages (see my pa- per, 1887, a). B. The extension of the cerebrum beyond all other parts of the brain, the occipital lobes overlapping the cerebellum even when the latter is allowed to displace the former. For the relations of these parts in the anthropoid apes, see my paper, 1884, g. C. The lapping of the temporal lobe over the optic tract, as shown by the two interrupted, curved to Bregma, and Estl- lines on the right (left of the fl ff- mated at Twelve Weeks; ,,,„% o \ & 1828. X 1. The sped- „'•,„ „. men was received In 8 '*'=■ -'''S'- °'<' illustrates: A. alcobol, sUU enclosed by The general form of the bodv and the membranes. After Umbs at thi'! nerinrl removal It was pinned '™"^i;,"' ^ . P°"°"- to loaded cork and kept B. The visibility of all the en- under alcohol during cephalic segments, excepting the Sllnf"S^Situ°ieanl diencephal; even this may here- expression are note- garded as represented by the op- y9.^!?yr ana have been tic nerve, dimly seen through the indentation at the ventral margin of the cerebrum. C. The marked preponderance of the cerebrum. D. The absence of the transi- tory fissures; compare, however, the right hemicerebrum, as shown in Fig. 746. E. The simplicity of the other regions, better shown in Fig. 746; the cerebellum is a narrow and undi- vided mass; the mesencephal presents a slight trans- verse depression between the pregeminum and post- geminum. § 43. The recognition of the brain as a segmented * This, the " isthmus cerebri " of some writers, must not be con- founded with the " isthmus rhombencephah " of others, which in- cludes a portion only of the mesencephalon (see Table I.). faithfully reproduced by the photograph and drawing ; the right side of the brain Is shown In Fig. 746, and the dorsal aspect was published in the New York Medi- cal Jmtrnal, February 16th, 1884, p. 177. terma RHINENCEPHAL rhinocele PROSENCEPHAL prosocele DIENCEPHAL dlacele MESENCEPHAL mesocele EPENCEPHAL eplcele METENOEPHAL- metacele organ is not dependent upon the determination of the- exact number of segments, their equivalency, or their boundaries. The postoblongata represents se vei-al poten - tial segments or neuromeres, but practically it may be regarded as one. Some even regard the entire oblongata together with the cerebellum and pons as a single seg- ment. § 44. Some idea of the diversity of opinion and usage among anatomists with respect to the number and desig- nations of the definitive segments may be gained from the table published in the first edition of this work (viii., 114), which is sub- stantially the same as in my paper, 1885, J, and in Wilder and Gage, 1882, 405. The appended Table I. in- dicates the difference be- tween the verbal schemas adopted by the Anatom- ische Gesellschaft in 1895, and by the Association of American Anatomists in 1897; the second is follow- ed in the present article. § 45. Commentaries on ths Schematic Medisected Brain, Fig. 675. — A. No two orig- inal workers in compara- tive neurology would be likely to construct schemas identical in all respects ; the one here presented is not satisfactory to me and I can hardly expect it to suit others. But with all its de- fects I believe it may serve three useful ends — viz. : (a) indicate the relative posi- tion of certain parts in the floor or the roof of the gen- eral cavity ; (*) facilitate the recognition of the essential identity of the brains of all vertebrates with that of man; (c) stimulate efforts toward the construction of a more perfect schema. B. Only mesal parts are presented, i.e., such as are divided in a medisection.* This excludes the cerebral hemispheres and olfactory bulbs, the lateral lobes of the cerebellum, and the elevations of the crura and quad- rigeminum at the side of the ventral and dorsal mesal furrows. C. The parietes present four degrees of thickness, viz. : (o) thin, e.g., the terma and the tuber in the floor, and in the roof the valvula and the lingula between the thick- ened quadrigeminum and cerebellum; (S) thick, e.g., the two just mentioned, the crura, and the oblongata caudad of the pons ; (c) reinforced, e.g:, the pons, chiasma, and precommiSsure ; (d) membranous, consisting only of the endyma and the pia, constituting a tela, e.g., the roofs of the metacele (metatela), of the diacele (diatela), and of the prosocele. The plexuses (metaplexus, etc.) are special modifications of the telas (§ 34). The meta- pore is here represented as an interruption of the meta- tela. If, as now seems probable (§ 83), it is an evagina- tion, there still remains the difficulty of determining its extent, and the best mode of representing it. D. For the sake of comprehensiveness certain features are included which do not occur in all vertebrates — e.g. : the metapore (in man and a few others) ; the pons (mam- mals only); the medicommissure (mammals and some * The callosum and fornix are omitted because their inclusion would have caused undesirable complications. rhombocele Fig. 674.— Schema of the Neuron (Cerebro-Spinal Axis), as if the cavity were exposed by the re- moval of the roof. The six en- cephalic segments are given a conventional spherical form, but without Intending to Imply that this is their actual shape or that all are separated by con- strictions. The main object of the diagram is to associate the encephaUc segments with their names and the names of their cavities. U4r REFERENCE HANDBOOK OF THE MEDICAL SCIENCES. Brain. Brain, Table I. — Compabativb View of the The Anatomische Gesellschapt in 1895. Partes ventrales. Partes dorsales. VI. Telencephalon. Pars optica h y p o - ( Corpus striatum ; rhinenceph- thalami. ( alon ; pallium. - ( Thalamus ; ( epithalamus. me ta thalamus; V. DiBNCEPHALON. Pars mamillaris hypo- thalami. IV. Mesencephalon. Pedunculi cerebri. ^ Corpora quadrigemina. III. Isthmus Rhombencephali. j Brachia conjunctiva ; velum Pedunculi cerebri. ( medullare anterius. II. Metencephalon. Pons. ■{ Cerebellum. I. Mtelencephalon. Medulla oblongata. Pars ventraKs. Pars dorsalis. Segmental Schemas Adopted by — The Association of American Anatomists in 1897. I. Rhinencephalon. Bulbi olfactorii with their tracts, part of the aula and of the precommissure. II. Prosencephalon. Palliums, connected by part of the aula and part of the precommissure. III. DiENCBPHALON. Thalami, including the chiasma ; genicula. IV. Mesencephalon. Crura and quadrigeminum. V. Epbncephalon. Cerebellum ; pons ; preoblongata. VI. Mbtbncephalon. Postoblongata. reptiles) ; the paraphysis (not found in mammals *) ; the chiasma (absent in teleosts). E. The dotted areas represent fibrous parts crossing the meson whether directly (precommissure) or oblique- ly (chiasma) ; the similar representation of the medicom- missure is not warranted by its cellular structure in mammals. F. Other differentiations of the substance of the parietes are not indicated, e.g., into the alba (white sub- stance) and the cinerea (gray). G. The hypophysis is notched and crossed by the broken line to indicate its twofold source, neural in) and J. The two indentations of the cerebellum, ental and ectal, represent respectively the fastigium (§ 95) and the furcal sulcus (§ 117), but without implying their exact collocation. K. The crista has been observed in comparatively few vertebrates and its morphological significance is undeter- mined (§ 366). L. The Absence of Flexures. — Granted that no brain is perfectly straight and that many are strongly flexed in one or more places, how many flexures shall be repre- sented and what shall be their extent? The only impar- tial condition of the axis is straight (§ 38). supracommissure para]>hysis. crista ^ep^hysis postcommissure ' geininuni cerebellum d.1. metacele nietatela metaplexus , dorsal zone royel^ - intersonal Knlcos - ventral zone -floor precommissure oblongata Fig. 675.— Provisional and Imperfect Schema of the Brain as if Medlsected ; Intended to approximate the " least common multiple " of the brains of vertebrates above the lancelet. A bbreviabions : —In the floor, at the sides of the precommissure, p.o. designates the olfactory division (pars olfaetoria) and p. t. the cerebral or temporal division (pars temporalis) of that commissure. In the hypophysis, 6, designates the portion derived from the euteron (prehypophysis), and n. the strictly nervous portion (posthypophysis). In the roof, s.a. designates the dorsal sac (soccus dorsoMs), and a. t. the decussation of the trochlear nerves (.deeussatio trochlearis). The numerals indicate the six deflnltlve segments beginning with the most cephalic (compare Fig. 680). enteric («) 1 146. The ectal line which elsewhere repre- sents the pia enveloping the brain should not be so inter- preted for the enteric portion. H. The indentation of the precommissure merely em- phasizes the relations of its two portions to the rhinen- cephal and the prosencephal respectively (§ 864). I. The indentation of the mesencephalic roof represents the transverse furrow which — in mammals only — de- marcates the quadrigeminum into a pregeminum and a postgeminum ; the former, I believe, is always the larger, but the ratio is not known to me. No attempt is made to indicate the intergeminum ("interoptic lobes" of Spitzka). * See the turtle's brain Fig. 680. The part is briefly discussed by Minot, 1898, 690, and by Studnl6ka, 1895. Vol. II.— 10 M. On the same principle the dorsal and ventral out- growths, paraphysis, dorsal sac (a.d), epiphysis, and hypophysis, are made to project nearly at right angles with the brain axis. In many vertebrates the hypoph- ysis tends caudad, but in man it tends rather in the opposite direction, and in the goose-fish (Lophius) it lies far cephalad of the rest of the brain. N. Tfte Porsal and Ventral Zones. — It is conceded that the myel is demarcated by an interzonal sulcus {'^sulcus limitans ventriculorum " of His) into a dorsal zone which is sensory and a ventral which is motor ; also that the sulcus and zones are represented more or less distinctly in the caudal half of the brain. On the figure the sulcus is conventionally indicated by the segmental names, mesencephal, etc., and by the three lines connecting them. But I have as yet been unable to satisfy myself of the 146 Brain. Braiu. REFERENCE HANDBOOK OF THE MEDICAL SCIENCES. continuance of these features in the cephalic half of the brain (see § 153).* O. Comparisons ■will be made naturally and justly with (a) representations of the primary neural segments or true neuromeres hke, e.g., that of Charles Hill (1899, 1900) ; (J) the schema of Prof. Wilhelm His (1893) which was adopted in 1895 by the Anatomische Gesellschaft (His, 1895); (c) that of Huxley (1871); (d) my own suc- cessive attempts,' especially that in the first edition of this work, vol. viii., p. 114, which was substantially identical with that in the last four editions of Quain's " Anatomy. " From all four it differs in the recognition of the olfactory region of the brain as a definitive seg- ment; from the first it differs also in regarding adult rather than early embryonic conditions— thus in recog- nizing the final, actual, or definitive segments rather than the primitive or jDotential neuromeres ; from the second, in addition to minor points that may be mentioned later, it differs also in the greater regard for the conditions in the lower vertebrates; in the non -recognition of the " isthmus rliombeneephali " as a definitive segment ; in the method of numerating the segments and in the names of some. See also my papers, 1897, e, and 1899, c. P. Tlie Number of Segments. — On this point the differ- ences of opinion and usage are wide and radical ; my own views have changed more than once and may change again. No one admits more fully the need of further information and of more logical interpretation. The practical question that now confronts us — investigators, teachers, and students alike — is this : In the present state of our knowledge, ignoring no known conditions of the brain, adult or developmental, and assigning at least equal weight to the lamprey and to the hag as to man, what number of transverse divisions shall be recognized, so as to facilitate the exposition and comprehension of the main features of a highly complex organ while not hindering the elucidation of the raysteries as yet unsolved ? These divisions must be natural, not necessarily identical but at least comparable, and neither so few as to be use- less nor so many as to be inconvenient. The practical requirements are met by the numbers five and six. Five definitive segments were recognized in Quain and in the first edition of this work. Six are now recognized by both His and myself ; but, as will be seen later, the first of mine (rhinencephal) is not admitted by him, wliile I am unable to see a definitive segment in the " isthmus rhombencephali. "f Q. In regarding the olfactory bulbs, their tracts or crura, the pars olfactwia of tlie precommissure, and the corresponding portion of the aula, as constituting a definitive segment, the rhinencephal, I may be unduly influenced by the conditions in certain other vertebrates (Figs. 680, 790, 791, and 794) and by the considerations briefly outlined in 1897, e ; but I feel that scant justice has been dealt hitherto to this probably primitive por- tion of the brain. R. Ths Developmental and Structural Disparity of the Segments. — Whatever number of definitive segments any anatomist admits, he will hardly claim that they are identical in either structure, mode of development, or relation to the primitive neuromeres. According to Charles Hill the mesencephal represents two neuromeres, and there certainly are several in the oblongata. S. The Relative Size of tlie Segments. — This point is an- * Burckhardt has represented tlie zones and other leatures by an elaborate system of colors ; 1895. t Should the " isthmus rhombencephali " be regarded as a deflnltive segment? In the early letal brain of man, the cat, and perhaps some other mammals, there is a neck-like region just caudad of the mesen- cephal. Professor His names this region " isthmus rhombencephali," and apparently regards it as co-ordinate with the other Ave segments recognized by him (1893, 173-174; 1895, Suppl. Bd.,157). But these same specimens, and indeed many of the figures of Professor His, present an equally distinct constriction cephalad. Even if the former represents the second of the two neuromeres which Charles HUl credits to the mesencephal, it is not easy to see why one of these regions, so insignificant in the later stages, should be reckoned as a definitive segment rather than the other. This point has been formu- lated independently by Dr. Stroud in the title of his paper, 1899, a, "If an Isthmus Ehombencephali, Why Not an Isthmus Prosen- cephall ? " from which Fig. 671 is borrowed. alogous to that respecting the direction of the axis of the entire brain (L). Even were the preponderance of the cerebrum in man and other mammals to be indicated the precise ratio would not be easy to fix. But in some sharks the cerebellum is very large ; in Teleoats the mes- encephalic lobes are most conspicuous ; in Ohimae)'a the dieucephal is greatly prolonged (W., 1877, a) ; in the elec- tric ray the postoblongata (metencephal) equals in size the remainder of the brain. Finally, to offset the relative in- significance of the olfactory bulbs in the Primates and their total absence in certain Cetacea, they compare favor- ably with the other segments in many Reptiles and Am- phibia, in the hags (Fig. 790) they are as wide as the cere- brum, and in the lamprey (Fig. 789) they surpass it in bulk. There seems to be no escape from the conclusion exemplified in the schema, viz., that the definitive seg- ments are potentially equal in size. T. The Numerical Designation of tlie Segments. — In ac- cordance with the rule (to which there is, so far as I know, but a single exception*) — -viz., that the members of any cephalo-caudal series of similar parts, e.g., ribs and vertebrae, should be numbered beginning with the one next the head— -anatomists have hitherto generally desig- nated the segment next the myel as last and the one at the other extreme as first. That plan is adhered to in Fig. 674, and throughout this article. The contrary enumera- tion was introduced by Professor His in 1893. It has been adopted by the Anatomische Gesellschaft, and there is likely to result confusion such as would attend the re- versal of the universal method of enumerating the cranial nerves. U. The Segmental Names. — As may be seen from the table of Hia reproduced in the latter part of the article Brain, Development of, and from the abstract of it in Table I., the most radical differences concern the two segments next the myel. The Association of American Anatomists follows Quain in designating the most caudal metencephalon and the next epenceplialon. The Anatom- ische Gesellschaft follows Huxley in applying meten- cephalon to the penultimate segment and designating the ultimate by myelencephalon.\ § 46. Mg. 676 illustrates : A. The great relative bulk of the head, constituting about one-half of the entire body. B. The indications of encephalic segmentation by slight furrows, represented by the converging lines upon the side of the head. C. The prominence of the mesencephal at this period, forming the "top of the head." D. The sharpness of the cranial flexure, whereby two of the segments appear in a dorsal view, and two in a ventral, while the fifth appears partly in both views, as shown by Figs. 677 and 678. E. The conditions of the eye and ear ; the greater dif- ferentiation of the manus than of the pes ; the presence of a short but distinct tail. § 47. Mg. 677 illustrates : A. The distinctness of the myelocele (" central canal ") even to the root of the tail. B. The sudden and great expansion to constitute the metepicele ("fourth ventricle"). C. The marked constriction between the mesocele and the metepicele. D. The existence, on the contrary, of the greatest *Dr. Gerrlsh informs me that In the famous work of Albinus, "Tabulse sceleti et musculorum corporis humani," 1747, the vertebrae, lumbar, thoracic, and cervical, are numbered from the caudal to the cephalic end of each series ; nevertheless, curiously enough, the ribs are enumerated in the more usual way. t Undesirable results or concomitants of the application of myelen- cephalon to the last (most caudal) segment, and of metemseptumn to the next (cerebellar) segment, are the following : (a) Disregard of the prior association of epencephaZon with the cerebellar segment bv Owen and (Juain. (6) Disregard of Owen's prior application of myet encephalon to the entire cerebro-spinal axis. Jc) Inconsistency, since the myel of myelencephalon obviously refers to the " spinal cord " which, however, is termed meduUa spi/nalis. (d) The appar- ent impossibility of having an appropriate or correlated convenient word term for the cavity of the last segment. MyetoeaUa (Eng. myelocele') was applied by me to the cavity of the myel (oanaUs centralis) ; myelenceptuHoeceUa would be cumbersome ; Ukewise ventriculm myelencephalicus. 146 REFERENCE HANDBCWK OP THE MEDICAL SCIENCES. Brain. Bralii, width of the metepicele opposite the ventral trunsveise furrow which is regarded by me as deinaroatiug the cephalic portion (epicele) from the caudal (mctaeele). E. The slightness of this transverse depression of the floor. With some human embrj'os of this and later stages (Kg. 671) there is a mark"! flexion (the pons flexurcful this entire region, at about the middle of its. length, sn that the two segments are easily distinguished. §48. Fif/. 678 illtmi rates: A. The greater width of the mesocele than of the diacele, so that the latter might be described as merely a passage between the former and the prosocele. B. The absence of any distinct thickening of the dia- ■celian wills to indicate the formation of the thalami. MESENCEPHAL EPENCEPIIAL /• _i.-- DIENOEPHAL FIG. 6T6.— Eight Side Of a Human Euibiyo, 18 mm, ion?, nrid Esti- mated to be Four Weeks of Age ; ;i74. >; fi Preparation.— The embryo wits received in at membranes, and had apparently lost much of the neck curval un-. so that the head Is more nearly than usual in line with ttie body. Tin- encephalic cavities were expfased by lemovirHf their ri>' ifs ; i lie i ir jglnal outline is Indicated by the broken linn. C. Themesal depression in tliedmrnlimi floor, probably representing the infundibulum. D. The lateral extension of the paraceles, the cavities of the future hemicerebrums. E. The presence of an i^evation of the paracelian floor, probably representing rhc caudatum. F. The continuity of the parietes at the junction of the prosencephal with the diencephal, and the absence of any indication oJ' plexal intrusion at this period. § 49. Oomnuiiitiirh-a upon Fig. 679.— K. Thisflgureisa combination of parts of Pigs. 677 and 678, as if the en- cephalic curvature were obliterated. This ideal straight- ening, a foi-m of normalization (§38), may be illustrated as follows : Flex the index finger upon itself as far as pos- sible ; let the nail represent the prosocele, the knuckle the metepicele, and the prominent middle joint the mesocele. From either the dorsal or palmar aspect only parls of the convex surfaces are visible; but if the finger is ex- tended all fall into one view, B. The main object of this figure is to facilitate a com- parison between the encephalic cavities of this early em- bryo and thof of the adult cat as shown in Fig. 686. The differences are much gi'eater in appearance than in . heart FIG. 677.— Dorsal Aspect of the Embryo Shown in Fig. 676: 374. X6. This and three of the foUowing figures (678, 679, 681) are too deeply shaded. See S 47. funis Fig. 6T8.- Ventral Aspect of the Embryo Shown in Figs. 676. 677, and 679; 274. X 6. The left arm has been removed. See 8 48. diacele mesocele reality, consisting mainly in the reduction of most of the cavities, the thickening of most of the parietes ; the great and irregular ex- tension of the later- .^I^S^^^^^^^fck. _ terma al masses, hemicer- ebrums, containing the paraceles ("lat- eral ventricles "). C. The resem- blance of this fig- ure to the appear- ance presented by the brain of Nec- turus (a salaman- der) after the re- moval of the roof is almost startling; see my paper, 84, a. § 50. The adult human brain pre- sents great and per- haps peculiar de- partures from the general type as based upon embry- ology and compara- tive -anatomy, and while anatomically admirable and physiologically nearly perfect, it rcLa,y fairly be char- acterized as. a morphological monstrosity. Among other general features, the segmental constitution of the organ is more apparent in many lower or more general- epicele metacele Fig. 679.— The Encephalic Cavities of the Embryo Shown in Figs. 677 and 678 Repre- sented upon One Plane. 141 Bralu. Brain. REFERENCE HANDBOOK OE THE MEDICAL SCIENCES. ized vertebrates, e.g. , the turtle (Fig. 680) and the hag (Pig. 783), and even in mammals where the cerebrum is less preponderant than in man. But with mammals the other segments are more easily recognized if the cere- brum and cerebellum are either tilted in opposite direc- tions as in the rabbit preparation (Pig. 681), or the former is also medisected as in the cat (Fig. 682), or both partly- cut away as in the sheep (Fig. 794). § 51. Mg. 680 illwtrates : A. The availability of this reptilian brain for the exemplification of certain features supracommlssure porta olfactory nerves epiphysis postcommissure geminum cerebellum I trocSlear j decussation metatela optic nerve cliiasma precommissure myel medlcommissure hypophysis Fig. 680.— Mesal Aspect ol the Medisected Brain of the Green Turtle, Chelone midas. X 1. From nature and from the paper of O. D. Humphrey, 1894. The letters B., P., D., M., E., and Mt., designate respec- tively the six segments, rhlnencephal, prosencephal, dienoephal, meaencephal, epencephal, and meten- cephal. The first and second are placed on the pial surfaces of the olfactory bulb and hemicerebrum ; the other four are within the cavities. of the organ ; it is large as compared with that of am- phibia and most other reptiles ; the cerebrum and cere- bellum do not overtop the other parts so as to obscure their serial relations; excepting the pons and callosum most of the commissures are represented ; and the cranial flexure is slight (Fig. 671). B. The departure from the schematic brain in two re- spects: (as) the reduction of the mesal portion of the rhinocele and prosocele to a slight cavity, the aula, open- ing laterad by the porta ; (6) the crowding of the cephalic segments caudad, occasioning the diencephalic flexure, and bringing the aula and porta dorsad of the diacele in- stead of cephalad of it. C. The elongation and close apposition of the three dor- sal outgrowths, paraphysis, dorsal sack, and epiphysis. D. The relatively large size of the olfactory bulb, and the duplicity of the olfactory nerve. § 53. Fig. 681 illustrates : A. The greater obviousness of the segmental constitution than with the adult human brain from any point of view. B. The smaller relative size of the cerebrum than in man or the cat (Pig. 682). C. The much less extent of the callosum than in man or the cat, making it possible to uncover the diencephal without the medisection required in the cat (Pig. 682). D. The presence of a distinct roof of the diacele, the interthalamic space, notwithstanding the cerebrum has been tilted. E. The relation of this roof, the diatela, to the habenas, the ridges demarcating the dorsal and ectocelian from the mesal or entocelian surfaces of the thalami. P. The non-adhesion of the thalamus to the hemicere- brum in any way such as to indicate that the former enters into the composition of the paracelian floor. G. The more nearly equal size of the lateral (pileums) and mesal (vermis) lobes of the cerebellum, and the con- comitant absence of the vallis which is so obvious on the caudal aspect of the adult human cerebellum (Pigs. 672 and 697). § 53. Mg. 68B illiistrates : A. The possibility, even with so high a mammal as the cat, of making a prepara- tion that, without disturbing the essential morphological features of the organ, may exhibit portions of all of the encephalic segments excepting the last, the meten- cephal. B. The tendency of three of the encephalic segments to overlap those caudad of them. The cerebellum, the epencephalic roof, partly conceals the postoblongata, metencephal, in its natural attitude; in the present figure it is tilted caudad. The mesencephal (gemina or optic lobes) is covered partly by the cerebellum and partly by the cerebrum, and also at the sides overlapped somewhat by the postgeniculums, elements of the diencephal ; in the figure these bodies are in deep shadow, crossed by the line 3 on the right, and on the left by the line lead- ing to the postgeminum. Finally, the cerebrum con- ceals the diencephal and mesencephal, part of the rhlnencephal, and even the cephalic slope of the cerebellum in the cat, while in man it alone is visible when the brain is viewed from the dorsal aspect (Pig. 664). C. The relations of the callosum and fornix to the two hemicerebrums, as lines of secondary ad- hesion between the two, the one dorsal and the other ventral. D. That the triangular area, hemiseptum, is real- ly only a .portion of the mesal wall of either hemi- cerebrum, which has been intercepted between the two lines of junction above named. E. That the interval, pseudocele (" fifth ventricle ") between the two hemiseptums, has no connection with the true encephalic cavities. F. That the callosum and fornix are in no sense parts of the roof of the diacele (third ventricle) : this is consti- tuted by (1) its proper endyma, (2) the pia covering this, as all other parts of the brain, (8) the pia pertaining to the fornix, which layer of pia, with the layer (2) and the intervening vessels, constitutes the velum. Q. Incidentally it may be remarked that the cruciate fissure in cats and dogs constitutes, as it were, a gash ■ I rebrum llinbria h ibena ill itela 1 h ilamus postgenlculum ~ epiphysis — pregeminum . postgeminum --.,., cerebellum FIG. 681.— Dorsal Aspect of the Brain of a Young Rabbit, the Cere- brum and Cerebellum Pushed in Opposite Directions. Preparafton.— While fresh, the cerebellum was tilted caudad and the hemispheres cephalad, and the velum removed ; the brain was then placed in strong alcohol so as to retain the desired shape. The segmental names are at the left, the names of parts at the right. The specimen has been lost or destroyed. across the mesal margin near the cephalic end of the hemicerebrum ; it appears, therefore, upon both the mesal and the dorso-lateral aspects. The well-known and easily experimented-upon motor areas of the limbs occupy the TJ-shaped gyre between the cruciate and coronal fissures. It does not follow, however, that the cruciate fissure and the human central fissure are homologous (§ 303) . § 54. Relative Size of the Segments in the Embryo and the Adult. — In the embryo at one period the mesencephal is the most prominent region, and it remains the largest in MESENCEPHAL EPENCEPHAL 148 REFERENCE HANDBOOK OF THE MEDICAL SCIENCES. Brain. Brain. some fishes ; in the adult human brain it is one of the least conspicuous. § 55. Segmental Overla/pping. — Although originally subequal in size, certain segments early manifest a ten- dency to extend beyond their neighbors in one or more directions. In man and the mammals generally this ■overlapping is in inverse ratio to the original size of the parts. The mesencfephal, at one period most prominent, is encroached upon by the diencephal at the sides, by the pons ventrad, the cerebellum dorsad, and all are eventu- ally covered by the cerebrum, primarily a comparatively insignificant portion of the brain. § 56. This segmental overlapping is, upon the whole, greater caudad than cephalad, most of the segments pre- senting something like the "rake " of the mast of a ship. The cerebellum, for example, not only extends both cephalad and caudad from its connections with the epen- cephalic floor, but iS tilted distinctly caudad (Figs. 670, ■687, and 693). § 57. Transections at any level caudad of the aula usually aflfect two or more segments. This is illustrated in the following diagrams (Pig. 683). § 58. Tlie Caudato-thala/mic JPhtsion. — The relations of the prosencephal to the diencephal are further compli- cated by the intimate fusion of the sides of the latter (thalami) with the floors of the former (caudatums). Al- though, therefore, in the early embryonic stages (Fig. 671) it is very easy to distinguish between the two segments, there is some difficulty in the adult. For convenience, in the present article, the capsula (" internal capsule ") is § 59. TTie Segments Primitivdy Mesal and Single. — This view is generally accepted with regard to the diencephal and the parts caudad of it on account of the fainiliar A. Fig. 683.— Diagrams Illustrating the Lateral Overlapping of the Mesen- oephal by the Two Segments CepHalad of It. The transverse axes of the prosencephal, diencephal, and mesencepbal are indicated by the lines 1, 3, 3, respectively; in A they are directed laterad, as in the early embryonic stages ; at B they are inclined caudad, and tran- sections at a or b would cut two or three segments instead of one. conditions of early development. The prosencephal like- wise, although commonly described as a pair of lateral masses, is single in "fishes" (see the figures and state- ments in connection with that segment, §§ 158-163). no. 682.— The Brain of a Cat from the Dorsal Aspect, After the Callosum and Fornix had been Divided and the Hemicerebrums Divaricated ; 474. X 2. 1 Ar tery (precerebral ?) : 2, artery joining 1, perforatmg tbe callosum from the velum ; 3, 4, lines of division of the a■ V> postcon 1 1 V myelocele Fig. 684.— Cast of the Encepbalic Cavities, Ventral Aspect ; approxi- mately correct. X 1 (?) (From Weisker, modlfled.) The names at the right, doubly underlined, designate Ave divisions of the en- cephalocele, together with the slender myelocele (central canal of the spinal cord). The metacele and epicele together constitute the " fourth ventricle " of the text-books ; the mesocele corresponds to the aqueduct or iter ; the dlacele equals the " third ventricle " less the aula, which is the mesal part of the prosocele ; prosocele in- cludes all not already specified, viz., the mesal aula, the lateral paraoeles (" lateral ventricles "), and the two portas through which they are continuous. The names at the left designate the parts of the para«ele, viz., the cella, extending caudad from the porta ; the precomu, extending cephalad ; the medlcomu, extending in a spiral direction laterad, ventrad, cephalad, and mesad, succes- sively ; and the postcomu projecting caudad from the cella. 2 is placed near the tip of the right lateral recess of the epicele. The larger part of the figure is modified from a photograph of the wax model made by Weisker, of Freiburg. The metacele, my- elocele, and part of the epicele are from a cast of the cavities in a child. The ventral aspect was chosen in order to display to better advantage the uninterrupted series of mesal cavities, and the portas. DefccU.—I doubt whether any part represents the correspond- ing'cavity accurately. The portas are too long (compare Fig. 718) . The dlacele presents neither the orifice for the medicommissure (the presumed location of which Is Indicated by the dotted circle (1) just caudad of the portas) nor the marked ventral extension toward the hypophysis. The medicomua are not sufficiently curved ; in reality the extremity of each approaches the dlacele within about 2.5 cm.; the postcomua are too short ; the bound- aries of the epicele are vaguely and perhaps Incorrectly indicated, and the lateral recesses (2) should be longer. forms (Dipnoans, etc.); with birds and frogs the mesen- cephal is markedly tripartite (Fig. 682) ; with man and other mammals, and likewise with some other verte- brates, the epicele presents more or less extensive "lateral recesses" (Figs. 669, 684, 698). The embryonic dien- cephal protrudes at either side an optic Vesicle that be- comes the retina and optic nerve. § 61. Fiff. 684 illustrates : A. The continuity, general form, and relative size of the several divisions of the adult human encephalocele, as viewed obliquely from the ventro-dextral aspect. B. The obvious triplicity of the prosocele, and the existence of lateral extensions of the epicele. C. The slenderneSs of the mesocele as compared with its relative size in the embryo (Fig. 680) and m the adults of some other vertebrates (Fig. 685). D. The general modifications of the primitive and typical condition of the encephalic cavity which led the older anatomists, and still lead somtTof their modern successors, to regard the whole as compris- ing four "ventricles," a first and second (lateral), a '^ third," and a "fourth," the aula being ignored and the mesocele considered merely as a " passage from the third ventricle to the fourth." § 63. Fig. 686 illustrates : A. An arrangement and circumscription of the encephalic cavities in the adult cat (an accessible mammal), essentially identical with that in the human adult (Fig. 785> and fetus (Fig. 716), and in vertebrates genemlly. B. The great differences in size and shape be- tween the various divisions of the encephalocele; the' mesocele is little larger than the myelocele, and is tubular ; the diacele is narrow but high ; the meta- cele wide but shallow; the epicele is very irregular; the myelocele is patent throughout, while in man it is nearly obliterated. The epicelian lateral recesses are not exposed, so the triple constitution of a typical segmental cavity is exhibited only by the prosocele, with its mesal, aula, and lateral paraceles. C. The different constitution of the celian pari- etes. The roofs of the aula, portas, and metacele are membranous telas, with plexuses on the ental surface. D. The reduced thickness of the parietes near the rima, constituting the fimbria, one of the riparian or marginal parts. E. The apparent interruption of the wall of the medicornu at the rima ("great transverse fissure"). On close examination, however, although the proper nervous parietes are absent, the intruded pial fold . (paraplexus) is seen to be covered by the endyma reflected from the adjoining parts, so that the in- jected alcohol was completely confined. F. The not very obvious relation of the ectal f uitow, hippocampal fissure, to the ental elevation or colliculus, hippocamp; on the right the line from postgeniculum crosses the end of the fissure, which is not otherwise indicated. G. The relations of the alba (medulla) to the ectocinerea (cortex) and tlie entocinerea (" central tubular gray ") ; olfactory nerve olfM'.tory bulb cerebrum : thalaml : : geminum : : ; cerebellum : : : : postoblongata : hypophysis optic nerve myel FIG. 685.— Left-hand figure : Brain of Frog Seen from the Left After Removal of Parts of the Left Side; 654. X 1.5. Right-hand fig- ure : Enlargement of the Geminum (Mesencephal), so as to show more distinctly the lateral cavity of the mesocele and the orifice (comparable with the porta) by which it communicates with the mesal cavity. the metepencephalic entocinerea has been removed in ex- posing the cavities, but it is distinct and abundant at the sides of the mesocele (aqueduct), of the diacele, consti- 150 REFERENCE HANDBOOK OF THE MEDICAL SCIENCES. Brain. Brain. cinerea alba hemiseptum _ caudatum tuting the thalamus, and of the prosencephalic precor- nu, constituting the caudatum and — unexpectedly— the hemiseptum and column of the fornix, all vrhich were distinctly gray in the fresh preparation. H. The caudal extension of the cerebrum so as to reach the cerebellum, and thus conceal the lateral aspect of the intervening segments, diencephal and mesencephal. I. The fusion of the thalamus with the caudatum, of the diacelian side wall with the paracelian floor. The line of junction of the two segments may be regarded as indicated approximate- ly by the word dien. J. The absence or in- conspicuousness of the lenticula, claustrum, and insula (compare Fig. 783). K. The less width of the diencephal than in man, so that the genicu- lums maintain their prop- er morphological relation of cephalic (pre) and cau- dal (post), rather than of lateral, or " external, " and mesal, or "internal," as in man. L. The extension of the paraceles, the proper cav- ities of the hemicere- brums, caudad from the aula even farther than cephalad, thereby war- ranting the diagrammatic representation of the par- aceles as lateral exten- sions, not ceplialic only. M. The absence of a postcomu in the cat as in most other mammals, the exceptions being man, monkeys, seals, porpoises, and some dogs. N. The distinctness of the crista in the cat. It is not named on the fig- ure, but may be seen as a conical elevation at the cephalic side of the aula; the line from aula points at it. § 63. Oelian Circum- scription. — The facts of development and compar- ative anatomy, and anal- ogy with other hollow organs warrant the pre- sumption that the ence- phalic cavities communi- cate only with one another and with the myelocele. Any communication with the ectal surface is pre- sumably artificial, except- perhaps, at the meta concomitant completeness of the celian circumscrip- tion. C. The non-communication of the pseudocele witli the true cavities. (The meninges and blood-vessels are con- sidered under Fig. 801.) § 66. In tracing the continuity of the endyma at the meson it is best to begin with a region where a rupture could hardly occur in either floor, roof, or sides, and where also a transection is most readily effected when paracele (cella) medlcomu mesocele __~";^- epicele .— metacele myelocele Fig. 686.— The Encephalic Cavities ol a Cat, Exposed from the Ventral Side ; 479. X 2. 1, The valvula, which is so thin in the cat that the cerebellar folia show dimly through it (the line is interrupted just above the L of EPENCEPHAL) ; 2, the narrow space between the lateral aspect of the mesencephal and the overlapping hemicerebrum ; in anthropotomy this is commonly reckoned as part of the " great trans- verse Assure " ; 3, obliquely cut surface, left by the removal ot the caudatum and adjacent parts of the left hemicerebrum. Prepa/ration.—The brain was exposed from the ventral side and left in the calva for better support, the cavities were alinjected so as to harden the parietes and keep them apart. Successive sUces were removed until the portas and aqueduct (mesocele) and myelocele were exposed. With a narrow- bladed knife the walls of the dlacele (including the medlcommissure), epicele, and metacele were cut away obliquely ; also on one side (the right of the preparation, but the figure is reversed so that it appears on the left) the caudatum, hippocamp, and part of the thalamus, so as to expose the continuity of the precomu and medicornu. The olfactory bulbs were removed with the ventral portion of the cerebrum. The boundaries of the cinerea (cortex, etc.) and alba (medulla) were ascertained by com- paring the similarly exposed surface of a fresh brain ; some of the differences between the two sides are due' to a slight difference ot the section-levels. Defects.— The brain should have been prepared in a chromic-acid solution, or injected with the red mixture, so as to difterentiate the alba and cinerea. pore (" foramen of Magendie ") and the lateral recesses (§§ 78, 98). § 64. Endymal Continuity. — The endyma is the essen- tial and absolutely constant constituent of the celian parietes; hence in all figures purporting to illustrate celian circumscription the line representing the endyma should be distinct and uninterrupted, excepting where discontinuity has been demonstrated. § 65, Mg. 687 illustrates : A. The sharpness of the cranial or mesencephalic flexure in man. Compare the sheep (Fig. 794) and the turtle (Fig. 680). B The continuity of the endyma linmg the mesal series of cavities excepting at the metapore, and the the entire brain is to be studied in two parts, a cerebral and a cerebellar portion. This " place of election " is the mesocele (" aqueduct " or "■iter a tertio ad quartum mntriculum "). A. The endyma covering the floor of the mesocele may be traced caudad (actually almost directly ventrad) with slight depressions and elevations through the oblongata to the my el where it lines the slender myelocele, the "canal of the cord." B. Recommencing at the same point in the mesocele, the floor endyma turns quite sharply ventrad over the cephalic curvature of the crus, passes the albicans, and reaches a region where the floor is thin and frequently 151 Brain. Brain. REFERENCE HANDBOOK OF THE MEDICAL SCIENCES. torn in removing Hie brain. This is the tuber, commonly called "■tvber cinereum," which is continuous with the infundibulum, and thus with the hypophysis. The cephalic part of the tuber is reinforced by the chiasma, termatic a. \ dura precerebral a. copula precommissure terma splenium Telar vein pregemmum mesooele postcommissure postgemlnum optic n. cbiasma hypophysis I albicans postcribrum ~ yalvula llngula -- epicele nodulus metatela metapore myel ' myelocele Fics. 687.— The Mesal Cavities of an Adult Brain Exposed from the Left, with Their Immedi- ate Parietes. X .65. Pig. 801 represents the entire meson of the same specimen on a smaller scale, and its mode of preparation is there described. Defects.— la addition to those specUed under Fig. 801, the most serious are : (a) the non-representation of the postpontile recess, the mesal depression just caudad of the pons, shown In Fig. 703, 2; (b) the presence of the line curving dorso-caudad from the rostrum of the callosum ; (c) the imperfect indication of the membranous parietes of the dorsal sac, the pouch lying upon the epiphysis ; (d) the non-designation of the diacele. the ental margin of which presents a marked transverse ridge, sloping caudad into the tuber and cephalad into the optic recess. In Figs. 689 and 708, the chiasma and tuber are shown with the hypophysis attached ; but in Fig. 673 it is detached, leaving an orifice, the lura. C. Directly dorsad from the chiasma, the cephalic wall of the diacele is the terma (lamina terminalis, or I. cine- rea), so thin and delicate as not infrequently to be rup- tured during the removal or manipulation of the brain. The proper nervous material of the terma seems hardly more substantial than the lining endyma and the cover- ing pia, here represented by the ental and ectal lines. The ecteil aspect of the terma is shown in Fig. 711. D. Suddenly there is a marked thickening of the cephalic wall, from the reinforcement, so to speak, of the terma by a fibrous cord, oval or elliptical in section. This, the precommissure, connects the olfactory bulbs and portions of the cerebrum upon opposite sides, and hence belongs to both the rhinencephal and prosencephal ; the cavity just caudad and dorsad of it is the aula, the mesal portion of the rhinocele and prosocele ; §§ 363-364. E. From the precommissure caudad to the roof of the mesocele the course of the endyma is extremely irregular, and the nature and shape of the roofs are very diverse. The immediate roof is largely membranous, and the con- dition is further complicated by bloodvessels large and small, and by plexuses. Finally, the parts lying directly upon the meson differ materially from those just laterad of it, and as the chances are altogether against a medi- section being exactly mesal in the whole of its course, there is nearly a certainty that upon the first inspection one will miss anticipated features and see what one does not understand. F. The recognition and comprehension of the actual facts in a given preparation will be fa- cilitated by consulting the diagram (Pig. 735), and the representations of the brains of the cat and rabbit (Figs. 681 and 683). The important point to bear in mind is that the complete cir- cumscription of the mesal encephalic cavities would be unaffected were the entire cerebrum removed, including the callosum, hemiseptum (the lateral wall of the pseudocele), and fornicom- missure (the mesal continuity of the fornix), down to the point where the heavy line representing the endyma leaves the narrow, white area repre- senting the fomicommissure to cross the convex surface of the fornicolumn and be reflected upon the auliplexus. The details of this, the aulic and portal region, are more clearly seen in the en- larged figures of the porta (Figs. 731 and 719). G. From the auliplexus (at or very near the meson) or from the portiplexus (if the section plane passes through the right or left porta instead of the mesal aula) the endyma may be traced caudad upon the ventral surface of a mem- branous fold, the velum. Strictly speaking, between the endyma and the velum, which is a fold of pia, inter- venes the remnant of the primitive nervous roof of the diacele. This may persist in some animals, but in the adult cat and in man, so far as I am aware, there is practically nothing between the pia constituting the velum and the endyma. At each side of the meson there depends a more or less distinct vascular fringe, the diaplexus, continu- ous with the auliplexus, the portiplex- us, and thus with the paraplexus, these last three being successive mem- bers of the prosoplexus. H. The relations of the endyma to the velum and plex- uses are more clearly shown in Fig. 733, representing a transection of the diacele. There also are shown the re- lations of the habena. This is a low ridge following a curved line along the mesal aspect of the thalamus from the dorsal end of the porta to near the epiphysis ; it is covered by endyma, but just dorsad of it, dimly seen in the figure, is a shallow furrow, the habenal sulcus, from which the endyma is reflected first dorsad, and then me- sad, upon the velum and the diaplexuses. The habena unites with its opposite (fellow of the other side) at the supracommissure. The endyma line is seen to- leave the velum, and descend to the dorsal (really cephalic) surface of the epiphysis, whence it extends cephalad to and over the margin of the supracommissure, then into and out of the epiphyseal recess, and over the convex cephalic sur- face of the postcommissure ; thence it enters the meso- cele, where the tracing of its continuity was begun, only it is now the lining of the roof, the geminal bodies, in- stead of the floor. I. Continuing caudad, there is but slight change in the direction of the roof of the mesocele ; a great reduction in its thickness occurs in the transition from the postgem- inum to the valvula. The succeeding part, the lingula, is somewhat thicker and trends slightly dorsad, to become continuous with the cerebellum proper. The cavity here resembles a gable roof, with a sharp dorsal angle. The caudal slope is formed by the nodulus, a compara- tively massive mesal lobe ; but from its margin, common- ly more rounded than appears in this figure, the endyma 152 REFERENCE HANDBOOK OP THE MEDICAL SCIENCES. Brain. Brain. Table II. — Pbovisional Grouping of Some NEURAii Parts According to Their Segments and Some Other Characters. 1. Segment. 2. Chief constituent. 3. Cavity. i. Membranous portion. 5. Plexuses. 6. Thin and riparian parts. 7. Commissures, etc. 8. Some other parts. I. II. III. IV V. VI. Til. EMneuceph- alon. Prosencepha' Ion. Dienoepha- ion. lilesencepha^ ion. Epencepha Ion. Metencepha- lon. Myelon Bulbl oUac- torll. Cerebrum Thalaml . Quadrlgeml- num. Cerebellum . . Postoblon- gata. Myelon Ehinocoella. . . . Prosocoella (In- cluding the mesalaulaand lateral parar coellae) . Diacoella . . . Ehlnotela (In some "flshes") Prosotela (In- cluding the mesal aulatela and lateral paratelae) . Dlatela Mesocoelia . Mesoteladnthe lamprey). Eplcoella.... Metacoelia.. Myelocoella. Metatela. . . . Myelotela (In lumbar en largemeni ot birds). Prosoplexus (including the mesal auUplex- us and lateral paraplexus) . Dlaplexus . . . Taenia, flmhria, pala, terma. Habena Valvula. Eplplexus . . Metaplexus . Lingula.. Metaporus, Ug- ula, obex. Praecommissura (pars oltactorla) Frsecommlssura (pars temporalis), callosum, fornix. Supracommlssu r a , medlcommissura, chlasma. Postcomml s s u r a , decussatlones teg- mentorum. Pons Decussatlo pyraml- dum. Commissura ventra- lis, c. dorsalis. Prsecribrum, 11m en, crista. Pallium, Insula, len- tlcula, caudatum, paraphysis. Postcribum, tuber, hy- pophysis, epiphysis, genicula. G r u s , tegmentum, crusta, lemniscus, Intercalatum. Praeoblongaia, vermis, flocculus, deutatum. Pyramls, oliva, trape- zium. Conus, fllum. Is abruptly reflected, together with the pla which had cov- ered its caudal surface; these two membranes, closely united, and with apparently little or no trace of the primitive nervous roof, constitute the metatela. This is interrupted or modified at the orifice here called meta- pore, but commonly known as "foramen of Magendie"; in the present figure it is at the point where an artery appears. Later observations indicate that the above accounts of the metatela and metapore do not apply to all specimens; see §§ 77-83. § 67. Encephalie Variations. — Excepting as to the fissures and gyres, and the pyramidal decussation, treatises upon an- atomy seldom refer to varia- tions or anomalies of, the sur- faces or ental structures of the brain,* yet they are frequent, and sometimes significant, mor- phologically if not physiologi- cally. So far as I can deter- mine from my own materials, and from figures and descrip- tions, there is hardly a feature of the human brain respecting which it can be stated confi- dently what is normal, or how frequently certain peculiarities occur. § 68. Classification of the Parts of the Brain. — The fore- going account of the brain as a whole constitutes an intro- duction to the description of «ach of the six segments, be- ginning with that immediately succeeding the myel. § 69. Commentaries v/pon Table II. — A. It is substan- tially identical with Table VII. in my paper, 1896, h. Compare the tables in the first «dition of this work (1889, a). * The sub.1ect is treated with un- usual fulness by Krause, 1889, 193-195. precomu 4 interoerebral Assure Sylvian, f. - olfactory bulbl ^EHINENCEPHAI, Olfactory tract J caput Of caudatum 2 trochlearis nerve insula fornix 3 Cauda of caudatum habena medlcommissure thalamus pregeniculum postgenlculum epiphysis pregemlnum ) J-MESENCEPHAL postgemlnum ) PROSENCE- FHAL DIKNCEPHAL pons flocculus cerebellum EPENOEPHAL metatela postoblongata I- metenoephal — . MTEL Fig. 688.— Brain of the Sheep, dissected so as to exemplify the segmental constitution of the organ in mammals. From " Physiology Practicums." 1, Cephalic slope of the cut surface of the cerebrum ; 2, mesal wall of the paracele— at a higher level this would be one of the hemiseptums ; 3, horizontal cut surface of cerebrum ; 4, the mesal, vertical portion of the paracele ; 5, indicates the location of the ripa between the thalamus and caudatum, but it is overhung by the latter so as not to appear in this view ; 6, mesal furrow of the pregemlnum. From the cerebellum have been cut both caudal and dorsal parts. On the cut dorsal surface are seen the central alba and the peripheral cinerea, but the outline of the latter is diagrammatic only. At the sides are the tiers of foUums constituting the flocculus. From the cephalic end of the cerebrum have been cut the parts projecting over the olfactory tracts, but part of the cephalic slope is here marked 1. With the dorsal portion were removed the entire callosum and the fornix excepting the cephalic vertical part. This and the mesal walls of the paracele are really cut at a lower level than the larger cut surface on the left. On the right the insula has been exposed by pushing up and breaking oft the overhanging parts. The ectal sur- faces, covered by pla, are indicated by irregular lines representing the blood-vessels. The ental surfaces, covered by eudyma, are those of the caudatums in the paraceles, the habenas, medlcommissure, and dorsal pouch ; and the floor of the aula and portas. The Irregular line laterad of the habena and extending around the endymal area on the epiphysis represents a rlpa (shore line). It consists of the cut or torn edges of the pla from the dorsum of the thalamus and of the endyma from the habena which united to form a membranous roof of the dla- cele, the dlatela, which has been removed. Similarly the pial, dorsal surface of the thalamus is demarcated from the endymal surface of the caudatum by a rlpa which meets the other at the porta. The epiphysis, although a constituent of the diencephal. Is tilted caudad so as to rest upon the pregemlnum, and the mesal part is covered by the dorsal sack. 153 Bratn. Brain, REFERENCE HANDBOOK OF THE MEDICAL SCIENCES. and in Wilder and Gage, 1883, 409. From the tables of Schwalbe (1881, 397) and His (1893 and 1895) it differs especially in the absence of any attempt to indicate the relative " values " of the several segments upon embryo- logic or other grounds. B. Its purpose is twofold : (a) To indicate, according to my present information and belief, the number and constitution of the definitive encephalic segments. (J) To illustrate the verbal coiTelations betvifeen the names of the segments themselves (column 1), and those of (3) their major cavities, (4) their membranous parietes, and (5) their vascular plexuses. C. The Latin form of the names is employed (see § 10). III. Metbncbphal. — § 70. Synonyms: Metencepha- lon, after-brain, myelencephalon, macromyelon. § 71. Tabular Arrangement of Parts. — Chief part: post- oblongata (caudal portion of " medulla oblongata "). Cavity: metacele (caudal portion of "fourth ventricle"). Floor : postoblongata. Sides : restes (" restiform bodies ") and ligula. Roof : metatela and obex. Plexuses : meta- FIG. 689.— Ventral Aspect of the Entire Brain Stem. X 1. (From Qualn.) Compare Fig. 673. Tbe Boman numerals I.-XII. designate the twelve pairs of cranial nerves : ii, the optic tract, more com- pletely exposed than in Figs. 673 and 738 ; a, albicans ; c, insula ; CO, ventral column ; c 1, first cervical, or suboccipital nerve ; ce, cerebellum ; cl, lateral column ; d, ventral Assure of the myel, just cephalad of which is seen the decussation of the pyramids ; e, pre- genlculum ; /, lemniscus ; fl, flocculus ; 7i, hypophysis ; i, postge- niculum ; o, oliva ; P, cms ; pa, pyramid ; PV, pons ; r, " lateral tract of oblongata," direct cerebellar tract ; Sy, at the ventral mar- gin of the Insula, indicates where the"baslsylvlan Assure begins ; tc, tuber ("tuber cinereum"), between which and the hypophysis is the inf undibulum ; Th, thalamus, cut surface; X, postcribrum ("posterior perforated space") ; X X, precrihrum (" anterior per- forated space ");-!-, motor root of trifacial nerve. V Preparation. — The entire left hemicerebrum has been removed by an Incision described as passing (In the capsula?) between it and the thalamus ; on the right side are left the insula, the adjacent part of the frontal lobe, the olfactory tract, and the precribrum. De/ecfs.— Several parts, notably the alblcantla (o) and the floc- culus Cfi), are represented In a somewhat conventional way, and thecimbla (" tractus peduncularis transversvs ") isomltted. The crura, especially the left, are shaded so as to appear twisted. plexuses. Orifice or evaglnation: metapore ("foramen of Magendie"). Decussation: Dec. of the pyramids. Other ectocelian parts and features : Ventral sulcus ; ven- tral column; pyramid; oliva; arciform fibres; lateral column; funiculus of Rolando; tubercle of Rolando; cuneate funiculus; funiculus gracilis; clava; ligula; obex. Other entocelian parts and features: Mesal sul- cus; alacinerea; postfovea; eminentia cinerea. § 73. The postoblongata (Figs. 670, 688, 689, etc.) is so obviously a continuation of the myel tliat if there were no parts cephalad of it, and if it were wholly contained within the spinal canal, it would probably be regarded as merely a somewhat modified region of the myel, compai- able with the lumbar enlargement near its other extrem- ity, which also in birds contains a distinct and thin-roofed dilatation, the rhombocele.* There is, therefore, ample etymological warrant for the name macromyelon (large myel region), applied by Owen, and for myelencephalon (myel-like brain region), employed by Huxley, His, and others. On account, however, of its equally obvious continuity with the preoblongata (especially in animals lacking the pons, e.g., the turtle; Fig. 680); its location, mostly withm the cranium ; and the number, peculiarity, and vital importance of the nerves connected with it, the postoblongata is conveniently regarded as a definitive segmentf of the brain under the title, meteneephal. § 73. Nevertheless both the macroscopic and the mi- croscopic structure of the postoblongata are much better understood in connection with those of the myel. For more details the reader is referred to the articles Spinal Cord and Brain, Histology of tits. § 74. Fig. 689 illustrates : A. The ectal origins of the cranial nerves. B. The ventral aspect of the adult insula (comp. Figs. 678 and 781). C. The continuity of the optic tract with both genicu- lums. D. The decussation of the pyramids (see imder Fig. 673). , E. The representation of all six segments upon the ventral aspect of such a preparation, including the parts of what is commonly called the " brain stem. " § 75. The postoblongata differs from a corresponding length of the myel in size, shape, amount of alba, amount and arrangement of cinerea, the extent and form of the cavity, and the nature of its roof. § 76. In the myel the two halves dorsad of the com- missures are in contact ; this is the case also with the caudal extremity of the postoblongata ; but for most of its length the originally mesal surfaces are separated by a rapidly widening interval, so that what was mesal be- comes successively dorsal, and finally lateral, while what was lateral becomes approximately ventral. These changes materially increase the width of the segment. § 77. Metacele. — The cavity, a tube in the myel and caudal part of the postoblongata, is expanded into an irregular triangular fossa, the metacele or caudal part of the " fourth ventricle. " The roof of this cavity consists of only the lining eudyma and the covering pia, consti- tuting the metatela. § 78. Metapore (foramen of Magendie). — In 1836-37 Ma- gendie described (1837, 1-39) an. orifice in the roof of the " fourth ventricle " by which that cavity communicates with the subarachnoid space. Magendie designated the orifice as entree des cavites du cerveau or entree des rentri- cules cerebraux. In 1855 Luschka published a description and figure of the orifice, which he renamed /(wamc» Ma- gendii. In the present article these and -various other polyonyms are replaced by the mononym metapore, Lat- in metaporus, signifying an orifice in the metatela, the membranous roof of the metacele, the cavity of the me- teneephal. * This dilatation of the myelocele has also been called *iwws rhf^m- hnidalw ; and this name has likewise unfortunately been applied to the " fourth ventricle," the continuous cavity of the meteneephal and epencephal ; furthermore, there have come into use derivatives like " rhomboldal lip " and " secondary rhomboidal lip." + As stated in § 43, this region represents several potential segments or neuromeres. 154 REFERENCE HANDBOOK OF THE MEDICAL SCIENCES. Braiu. Bralu. § 79. Most later anatomical writers have admitted the existence of the metapore, but the descriptions are com- monly brief and the figures unsatisfactory. That by Key and Retzius is suspiciously symmetrical, although .pyramis Fig. 690.— Tlie Metapore (Foramen of Magendie) as Exposed by the Divarication of the Cerebellum and Oblongata ; 318. x 1. Prepa/ration.—tbe brain of an adult Swedish carpenter was re- moved with great care, by dividing the calva sagittally at the left of the meson, so as to avoid tearing membranous adhesions. The brain was supported on a bed of cotton ; the arteries and the arach- noid extending from the cerebellum to the oblongata were cut away and the two parts held asmider with Angers so as to expose the re- gion of the metapore. A photograph was then taken, upon which the drawing is based. After hardening, however, most of the cere- bellum was cut away and another photograph taken of the reduced mass. The' specimen and both photographs were shown at the meeting of the Association of American Anatomists, December 28th, 1892. Defects.— The right side of the cerebellum was displaced more than the left, giving rise to the marked obliquity. The metapore itself should be shown on a larger scale. The postcerebellar arteries are omitted ; they do not appear distinctly in the first photograph, and no record was made of their locations. This is unfortunate, ^nce in all the cases in which they are preserved their relations to the metapore are close. Had more of the caudal aspect of the cere- bellum been included, there might have been shown the line of at- tachment of the arachnoid at the boundaries of the postcisterna. The wavy lines on the dorsum of the oblongata hardly do .iustice to the vascularity of the pia covering that region. it is copied by Schwalbe; Henle's (Fig. 691) is more nat- ural. The best figures and the fullest description are those of Carl Hess, 1885, but few figures have the ap- pearance of having been based upon photographs. § 80. My own earlier scepticism was based partly upon the absence of any such orifice in the cat and sheep, and upon the presumption in favor of endymal continuity and celian circumscription. The steps of my conversion to the more common view are stated in the first edition of the Reference Handbook and in the papers there referred to. The examination of specimens carefully prepared for the purpose showed that: (1) The metapore is a normal and nearly constant fea- ture of the human brain at and after bh'th. (2) It exists also in apes and some monkeys. (3) There are two human types, viz. : (a) definite, as shown in Fig. 690; (b) indefinite, Fig. 691. The latter is the. more common. §81. Fig. 690 illustrates: A. The existence of a natural orifice in the membranous roof of the " fourth ventricle. " B. The simplicity of the form and relations of the met- apore in this specimen. It is mesal, symmetrical, and oval. C. The appearance of the metaplexuses just within the cephalic margin of- the metapore with no such extension upon the cerebellum as is shown in Fig. 691. § 83. Mg. 691 illustrates : A. The admission of the nor- mal existence of the metapore in the adult by so expert an anatomist as Henle. B. The attachment of an extension of the metatela from the cephalic border of the metapore upon the uvula and pyramis of the cerebellum. C. The extension of the metaplexuses upon the thus everted ental aspect of the metatela, whereas in the speci- men represented in Fig. 690 they barely appeared at the margin. D. The topographical relation of the contorted post- cerebellar arteries to the metapore. E. The relation of the flocculus to the lateral recess (Fig. 698) . §'83. I'he Metapore the Outlet of an Evagination. — In accordance with the general morphological relations of the germ layers Minot published (1893, 676) this passage: " Several writers have thought that the membrane [en- dyma] was broken through at certain points, but it prob- valUcula arachnoid pyramis Fig. 691.— The Metapore (Foramen' of Magendie) and Adjacent Parts Nearly as Represented by Henle ( "Anatomie," iti.. Fig. 232). Preparation.— la the absence of statement by the author, it may be said that the brain was probably removed in the usual way, and the cerebellum tilted cephalad so as to expose its caudal aspect and the dorsum of the oblongata. The left tonsilla was then cut out, ex- posing on that side the parts marked I, IX, and a continuation of the postcerebellar artery. I, metatela [velwn ntedullare postering), its lateral portion; II, lateral recess of the metepicele (fourth ventricle) opened by the re- moval of part of the metatela ; III, flocculus ; IV, epiplexus (plexus choroideus later aXis). Changes.— The boundary line of the tonsilla has been made more distinct than in the original. In the upper part has been introduced a Une to represent approximately the line of attachment of the arachnoid, constituting the dorsal boundary of the postcisterna (see Fig. 806). Defects.— The margins of the metapore are too sharply defined ; this is, perhaps, unavoidable when the parts are upon so small a scale ; it cannot be said to bear either way upon the question of the naturalness of the orifice, for the effect of tearing a tough mem- brane like the metatela would be to leave ragged edges. The rela- tions of the plexuses and accompanying strip of metatela are inade- quately. Indicated, and the writer regrets his present inability to elucidate them. The postcerebellar arteries are represented as if distributed only between the oblongata and cerebellum, and between theHbes of tjie latter (compare Fig. 806) . ■■#:■ ably IS really continuous throughout life. The fourth ventricle is to be regarded, then, as an expansion of the central canal permanently bounded by the original med- ullary walls. " In the following year, in a letter which he authorized 165 Brain. Brain, REFERENCE HANDBOOK OP THE MEDICAL SCIENCES. me to publish in my paper (1893, d), Minot made the im- portant suggestion that the metapore represented the mouth (proximal orifice) of an evagination of the endy- ma. Mrs. Gage found (1893) an evagination in Amia, and in BiemyctyltLs a distal orifice. Recently J. A. Blake has gone over the whole subject and shown (1898, 1900) by an admirable series of sections that in cats and dogs and other mammals there is a caudal protrusion of the metatela in the form of a closed sac, but that in man and apes, and (with modifications) in other primates, the larger part of the sac disappears so as to leave a free communication between the " fourth ventricle " and the postcisterna, a subarachnoid space. Blake's paper is ac- cessible to American anatomists, and the bibliography is very complete ; much, however, remains to be done. § 84. The increased cinerea of the postoblongata con- sists of (1) the continuous expanded masses of the ven- tral and dorsal cornua, especially the latter, which, with the modified ventral commissures, constitute the metace- lian floor; (2) special masses of cinerea, more or less completely separate, the nidi of Spitzka, the niduli of Henick, the "nuclei" of most writers, constituting the ontal or deep origin of certain cranial nerves, and pre- sumably representing detachments of the cornua ; (3) the dentatnm oUvce, or olivary nucleus, a capsule of cinerea within the oliva, resembling the cerebellar dentatum. § 85. Mg. 69S illustrates : A. The insensible transition from the myel to the postoblongata, and thus from the myel as a whole to the brain as a whole. B. The apparently sharp demarcation between the «pencephal, represented here mainly by the pons, and the prepefluncular fossa prepedimcle \ \ prepeduncle Ungula medipeduncle postpeduncle restis X yusipt^uuuciu pyiuiiiiu uiiva ii ripa Kg. 693.— Left Side of the Metepencephal (After the Removal of the Cerebellum) ; 2,136. X 1.5. 1, Emergence area of the trifacial nerve, the larger the sensory root, the smaller the motor ; 3, the fibrcB arciformie partly encircling the oliva ; 3, Une of emergence of the accessorius and of the dorsal roots of the spinal nerves ; 4, continuation of the lateral column of the myel ; 5, line of emergence of the ventral roots of the spinal nerves ; 6, ventral column ; 7, ven- tral (mesal) Assure; 8, myelocele: 9, dorsal (mesal) Assure; 10, funiculus gracilis, the oWongatal continuation of the myellc dorso- mesal (" posterior median ") column, enlarging cephalad Into the dava; the clava and funiculus together are sometimes called " pos- terior pyramid"; ll, "posterior median Assure"; 12, funiculus cuneatus: 13, the shaded band represents the mesal portion of the metacele (caudal part of the " fourth ventricle ") between the restes (" restiiform bodies ") of the two sides ; 14, acoustic tubercle, over which run the acoustic striae, which are not shovm ; 15, tubercle of Rolando, the continuation of the unspeclAed funiculus of Rolando, Interpolated between the funiculus cuneatus and the emergence line of the dorsal roots. De/ecfs.— Although good in general form and showing the oliva and its arciform Abres (2) with unusual distinctness, the specimen does not exhibit the several columns very clearly, and the lines of demarcation, excepting the " posterior median Assure," are taken from other preparations and from Agures ; this applies also to the lines upon the pons indicating the passage of the caudal fasciculi entad of the cephalic. The dotted lines demarcating the sectional areas of the peduncles are only approximately accurate. The facial and acoustic nerves are not shown, or the acoustic strise (see Jig. adjoining segment. In reality, however, not only do the cephalic and caudal margins overhang the adjoining sur- faces to a certain extent (see Fig. 703, 1 and 2), but it is by no means certain that the pons covers no more and no less than the epencephalic portion of the oblongata. In the sheep and cat, for example, the trapezium, here in- visible, is exposed (Fig. 794), while with many lower vertebrates the pons is rudimentary or absent altogether, and the boundaries between metencephal and epencephal must be otherwise determined; e.g., the turtle, Fig. 680. C. The lapping of the cephalic portion of the pons over the caudal, giving the appearance of a twist or rota- tion of the medipeduncle upon its own axis to the extent of the fourth of a circle. D. The relation to the oliva of the arciform fibres (2), which appear to be derived from the pyramid and to pass around the caudal end of the oliva to enter into the com- position of the restis and postpeduncle. E. The projection of the right clava beyond the left, a marked lack of symmetry in this specimen. F. The ripa, or line of demarcation between the gen- eral, pial surface of the myel and oblongata, and the en- dymal, metaceliau surface. The ripa consists of the pia and endyma with, in some specimens (Fig. 702), a thin intervening lamina of nervous substance. G. The prepedunoular fossa, a shallow depression on the dorsolateral surface of the prepeduncle, near the medipeduncle. § 86. The visible longitudinal divisions of the postob- longata do not correspond altogether with the myelic columns. The ventral column (Fig. 673, i, Fig. 689, ca. Fig. 693, 6) continues cephalad partly in the pyramid of the same side, as would naturally be expected, but mostly dips entad of the pyramid and oliva and forms longitu- dinal fasciculi near the meson farther dorsad. § 87. Of the lateral column (Fig. 689, d, and Fig. 693, I) a large part crosses at the decussation (shown in Fig. 689, but not always visible) to constitute mainly the pyramid of the opjDosite side. Some of the fibres join the restis of the same side, constituting the " direct lateral cerebellar tract. " The rest of the lateral column dips en- tad of the oliva and " forms the longitudinal fibres of the substantia reticularis grisea." § 88. The dorsal column of the larger portion of the myel is displaced in the cervical region by the dorso- mesal (" posterior median ") column (Fig. 693, 10) ; this, in the postoblongata, is called funiculus gracilis. Near the apex of the metacele it presents a distinct enlarge- ment, the clava (Fig. 693), cephalad of which the funicu- lus is no longer distinct. Between the funiculus gracilis and the lateral column (Fig. 693, 4) there intervene, in the postoblongata, two funiculi, of which the more lateral (15) is regarded as the direct continuation of the dorsal column of the myel, but is commonly called funiculus of Rolando, sometimes " lateral cuneate " ; between it and the dorso-mesal column {funiculus graeilis) intervenes another interpolated funiculus, the cuneate (13) ; this and the funiculus of Rolando appear to enter into the com- position of the restis (" restif orm body ") which is con- tinued as the postpeduncle into the cerebellum ; but, ac- cording to Quain, this relation is rather apparent than real, the components of the restis and postpeduncle being {a) the arciform fibres (Fig. 693, 3) from the ventral column, and (b) the " direct cerebellar tract " of the lateral column. § 89. The increased bulk of the postoblongata is due also in part to the entrance (or exit) of the roots of the accessory, hypoglossal, vagus, and glossopharyngeal nerves, which are more numerous than the spinal nerve roots upon a similar length of the myel (see Figs. 673 and 689). § 90. Fig. 693 illustrates : A. The general topographic relation of the cerebellum to the segments just cephalad and caudad, and to the ventral portion of its own seg- ment, through the three pairs of peduncles, prepeduncle (5), postpeduncle (3), and medipeduncle (the cut area crossed by line 5 on the right and by lines 3, 4, and 5 on the left). B. The tendency of anatomical writers to ignore the existence or traces or morphological significance of the thin or membranous portions of the encephalic parietes (see my paper, 1891, b). 166 REFERENCE HANDBOOK OF THE MEDICAL SCIENCES. Braiu. Brain. IV. Epencbphal.— 8 91. Synonyms.— 'Epencepb&lon; metencephalon ; cerebellar segment ; hlndbrain. § 92. Principal Pm-ts.— Floor: preoblongata and pons. Roof: cerebellum and lingula. Sides: peduncles. Cavity: epicele with lateral recesses. Ectocinerea: cortex. Entoclnerea: dentatum, fastigatum, embolus, globulus. Chief cerebellar divisions: (mesal) vermis; (lateral) pileums ("hemispheres"). Flocculus and para- flocculus. § 93. Bounda/ries.— The epencephal may be defined as Including as much of the brain tube as intervenes be- FlG. 693.— Dissection ol the Peduncles. X0.5. (I^omQualn, alter Sap- pey, and HlrscMeld and Levlell^.) 1, Mesal sulcus ; the line crosses the middle of the wide cut surface Of the medlpeduncle : 2, mesal sulcus at the place of emergence of the acoustic striffi ; 3, postpe- duncle, continuous with the restis ; the cut end of the postpeduncle Is crossed by the line, 2; 4, the clava, the swollen portion ol the fu- niculus gracilis ; 5, prepeduncle ; 6, lemniscus ; 7, lateral sulcus of the eras ; 8, pregeminum, the p(»tgeminum just caudad. Preparation.— On the left, the three peduncles are cut short ; the right half of the cerebellum is cut obliquely, and tilted laterad, so as to show the connections of the prepeduncle and postpeduncle. Z)e/ecf«.— There is no evidence of the lines of division, ripas, of the endymain exposing the metepicele ("fourth ventricle"), or of the existence of the valvula and lingula between the prepeduncles. tween the membranous portion of the roof (metatela) and the decussation of the trochlearis nerve, together with the corresponding regions of the floor and sides and the encompassed cavity, the epicele. § 94. Mg. 694 illustrates : A. The general aspect of the adult cerebellum from the side. B. The location of three main sulci, furcal, cacuminal, and peduncular. § 95. Epicele. — The epencephalic cavity includes the cephalic ("anterior") portion of the "fourth ventricle" .together with its dorsal extension (fastigium) into the cerebellum, more or less triangular in form. According to Blake (1898-1900, 89-90) the cavity of the cerebellum has at first a greater dorso-ventral extension which is reduced by the fusion of the opposed walls. § 96. Lateral Becesses. — ^By this name are commonly known the pair of extensions of the " fourth ventricle " laterad and ventrad (Figs. 684, 695, and 698). Their walls are partly membranous (metatela) and partly substantial (sides of oblongata, peduncles of flocculus, and certain nerve roots). They might with equal appropriateness, perhaps, be described under the metencephal, and the diflSculty in determining the segmental assignment is very naturally included by Blake (1898, 104) among the reasons for the non-recognition of two segments in this region. § 97. Mg. 695 illustrates : A. The embryonic continuity of the endyma and more substantial elements of the parietes around the lateral recesses at this stage (see § 98). B. The corrugation of the thin portion of the par- epicelian parietes preparatory to the formation of the epiplexus. § 98. Outlets of the Lateral Recesses. — Although closed in the embryo (Fig. 695) the ventral ends of the recesses are commonly described as open, constituting communi- cations with the subarachnoid space even when the meta- pore does not exist. I have been disposed to regard these cacuminal s. furcal sulcus peduncular sulcus FIG. 694.— Left Side of the Cerebellum of an Aged White Man ; 3,434. X 1. (From Stroud, 1897, a.) The outUnes were drawn with the camera lucida. orifices as artifacts from the readiness with which the membranous adhesions of that region are torn during the removal and examination of the brain according to cus- tomary methods. But the histological and embryological researches of Blake seem to show that in man and in mam- Fia. 695.— Transection of the Brain of an Embryo Babbit, Sixteen Days Old. (From KOUlker.) X 65 ; enlargement of part of Fig. 669. mals generally the ends of the recesses are opened by the more or less extensive disappearance of the membranous parietes. § 99. Mg. 696 illustrates, in addition to points also shown in Mg. 694 ■' A. The great depth of the furcal sulcus. B. The absence of the lingular foliums (§ 119). § 100. Preoblongata. — The floor of the epicele is the preoblongata,' continuous with the postoblongata and with the crura. In the turtle (Fig. 680) and other non- mammals there is no obvious line of demarcation. 16Y Bralu, Brain. REFERENCE HANDBOOK OP THE MEDICAL SCIENCES. § 101. Pons. — In mammals the preoblongata is so markedly reinforced by a transverse fibrous mass, the pons, that it is easily recognized ; but the width of the peduncular sulcus f ureal s. cacuminal s. Fig. 696. Mesal Aspect of the Cerebellum of an Adult Male Negrfa ; 3,118. X 1. Traced from a photograph. (From Stroud, 1897, a.) pons varies so greatly that its margins can hardly be ac- cepted as the boundaries of the entire segment. Compare the turtle (Fig. 680) with the sheep (Fig. 794) and man (Figs. 673 and 689). § 103. Peduncles. — At and near the meson the connec- tions of the cerebellum with the adjoining segments are thin ; tlie hngula is relatively atrophied (Fig. 703) and the inetatela wholly membranous (Figs. 670 and 687); but laterally the cerebellum has massive continuations, constituting three pairs of peduncles: a cephalic (prepedun- cles) to the mesencephal; a caudal (postpeduncles) to the metencephal and myel, and an intermediate (medi- peduncles) to the pons, part of the same segment. § 103. The peduncles constitute a continuous mass of alba at either side, but their relative positions and extent are pretty well determined by various methods, anatomical, microscopical, and experimental.- The medipeduncle is the largest and most lateral; it is mainly continued from the lateral lobe of the cerebellum to the pons, where the fibres cross the meson, interdigi- tating with their opposites, and form- ing a i-elation with the cinerea. The postpeduncle mainly connects the ver- mis with the restis, while the prepe- duncle connects chiefly the dentatum with the mesencephal and parts far- ther cephalad. The dorso-lateral as- pect of the prepeduncle presents a distinct shallow depression, the prepe- duncular fossa (Fig. 693). . § 104. The relative location and di- rection of the three peduncles on the right side may be illustrated by the digits of the right hand. Hold the hand with the fingers down, the thumb pointing backward, the index forward, and the other three fingers, slightly overlapping, outward between them. The palm may then represent the cere- bellum, the poUex the short and sharply curved post- peduncle, the index the longer and less curved prepe- duncle, and the other three fingers the intermediate and tliickest medipeduncle, continuous with its oppo- site through the pons. § 105. Mg. 697 ilhistrates : A. The lapping of the tonsillsB over the uvula. B. The location of the flocculus and the com- mencement of the peduncular sulcus. C. The relative position and size of the three pe- duncles. § 106. Flocculus and Parafloeculus. — Attached to the medipeduncle by short peduncles of their own are small foliated masses, the flocculus (in two lobes) and the parafloeculus (in one) (Figs. 698 and 701). Contrary to the implication of the names, the parafloeculus is really attached mesad of the floccu- lus ; in Fig. 698 they are twisted so that the reverse appears to be the case. The peduncle of the floc- culus forms part of the wall of the " lateral recess " (Pig. 698). Little is known of the functions of these parts or of their homologues in other animals. According to Stroud (p. 96) the parafloeculus is much larger in the cat and capable of division into a supraflocculus and mediflocculus. § 107. Fig. 698 illustrates : A. The location and form of the flocculus, witli its two divisions and rounded folia, and of the smaller parafloeculus. presenting but slight traces of foliation. All are attached to the medipeduncle, and the flocculus is sometimes called the peduncular lobe. B. The general location of the lateral recess (2), or parepicele, between the peduncles cephalad, the restis and other parts of the postoblongata mesad, and the flocculus stem laterad; its peculiar relations with the glosso-pharyngeal and vagus nerves are in- adequately shown and need special preparation and study. C. The twisting of the peduncles of the flocculus and parafloeculus whereby their real attachments are appar- ently reversed. The" parafloeculus, although its name peduncular sulcus medipeduncle postpeduncle lingula epicele Fig. 697.— Caudal (" Lower " or " Posterior ") Aspect of the Adult Cerebellum. A little l>?gs than natural size. (From Kdinger, Inverted and slightly modified.) 1, Part of Uie riglil quadrangular lobe. The cut ends of the peduncles are dotted ; the large medlpedunclcs extend latero-dorsad into the lateral lobes; the fiocculi are attached to the medf- peduncles. The continuity of the vermian divisions with those of the lateral lobes is not apparent upon this aspect. Defects.— In addition to the general remark made under Fig. 700 the followiiif!: special deficiencies are to be noted : (1) , There is no line to represent the divided endymii of the metatela along the caudal (here upper) side of the cavity (epicele) ; all this region requires elucidation in respect to celian circumscription ; (2), the omission of the ple.N- uses and nerve roots ; (3), the postvermis should be more deeply shaded to indicate iis depth below the level of the tonsilte, which also are really almost in contact ; (4), on this, or on Fig. 700, the vermis should present a line indicating the reflexion of the arachnoid. 158 REFERENCE HANDBOOK OF THE MEDICAL SCIENCES. Brain. Brain. suggests a lateral position, really is attached mesad of the flocculus; see Fig. 701. § 108. The cerebeUwrn is essentially an arch over the epicele (cephalic part of the "fourth ventricle") (Fig. flocculu.s paraSocculus ■piG. 698.— Caudal Aspect of the Right Flocculus and Adjacent Parts ; 2,238. X 3. 1, Endyma at the left side of the epicele; 2, right lateral recess, laid open ; 3, ollva ; 4, pyramid ; 5, trifacial nerve ; 6, ab- ducens; 7, facial; 8, acoustic; 9, glosso-pharyngeal ; 10, recess latero-dorsad of ollva. PreporaMon.— The cerebellum was removed by division of the peduncles to near the floor of the epicele, and the postoblongata by a transection just caudad of the pons ; the lateral recess (2) had already been torn open, as usual, in removing the brain, and its en- tire extent and exact form are not determinable from this prepara^ tlon (see Fig. 684). 699). sists human Fio. 699. — Caudal Aspect of the Cerebellum and Oblon- gata of a Fetus. (Size and age and ma^iflcatlon un- certain, specimen and notes having been lost; it proba- bly resembled quite nearly the specimen shown in Fig. 373.) a. The kilos. postsemllunar peduncular sulcus This condition exists in the embryo, and per- in many of the lower vertebrates. The adult organ, however, is a foliated mass of complex fibrous and cellular structure, well meriting the adjective hypertropMed, applied to it by E. 0. Spitzka. § 109. Mg. 699 illustrates: A. The large size of the epi- cele at this period, as compared with the thickness of the parietes. B. The ex- tensions lat- ero - ventrad constituting the parepi- celes or " lat- eral recesses" (compare Figs. 384 and 395). C. The non-appearance of the mesal lobe, vermis, at this period and the absence of sulci upon the lateral masses, pileums. D. The continuity of the riparian part, a, the kilos (" posterior velum "), along the line of junction of the ectal pia and ental endyma, they not being represented distinctly; if their torn edges were distinct they would con- stitute the cestus. The cestus and kilos indicate the line of attachment of the metatela. § 110. Aspects of the Cerebellum.— In. the natural condition of the adult brain the rounded margin of the cerebellum demarcates two surfaces looking re- spectively " upward " and " down- ward." But in accordance with the general principle of normalization (§ 38) and by analogy with the simpler case of the epiphysis (§ 154) the cere- bellum is here regarded as if projecting dorsad at right angles with its supporting portion of the brain- axis, the oblongata (Fig. 708). The two main surfaces become therefore cephalic and caudal, but they are not sharply delimited. § 111. Pileums and Vermis. — The adult cerebellum comprises a mesal lobe, the vermis, and two lateral masses, the pileums, commonly called "hemispheres." On the cephalic aspect, the vernjis (prevermis) is promi- nent (Fig. 700) ; but on the caudal the lateral lobes project decidedly beyond the postvermis, the surface of which is thus at the bottom of a deep mesal crevice, the vallis ("vallecula") (Fig. 697). § 113. Foliwns, Sulci, and Lobes. — The entire surface of the adult cerebellum presents numerous lines, for the most part parallel and having a generally transverse direction. These lines represent crevices of greater or less depth, the sulci, and the intervening thin plates are the folia. Certain of the interfoliar crevices are so con- stant, deep, or distinct as to warrant the recognition of the intervening groups of folia as lobfes. The commonly received division or the two regions of the cerebellum into lobes is indicated upon the figures. I am free to admit, however, that I am by no means fully satisfied therewith. § 113. Fig. 700 illustrates : A. The natural tilt caudad of the cerebellum, so that its normally cephalic surface looks dorso-cephalad, even when the oblongata is held in the cephalo-caudal plane. B. The extension of the cerebellum, so as to overhang the postoblongata. C. The enormous preponderance of the pileums (lateral lobes) over the vermis (mesal lobe) in the adult ; compare however, Fig. 699. D. The slight demarcation between the vermis and pileums on this aspect. E. The appearance of part of the postsemllunar lobes, and of the peduncular sulcus, both these appearing partly also upon the caudal surface. F. The connection of the two cacuminal (presemi- lunar) lobes by means of a single folium, the cacumen. § 114. Coj-to (ectocinerea). — Each folium consists of a central lamina of alba and a covering of cinerea having a peculiar cellular structure; see the article Histology of the Brain. '•^<. central lobe Ungula 77'^ A valvula prepeduncle FIG. 700. — Cephalic (" Upper " or Anterior ") Aspect of the Adult Cerebellum. From Ed- Inger, inverted and slightly modified ; a little less than natural size. 1, The ala or lateral portion of the central lobe. De/ecfs.— The original figure is obviously diagrammatic ; it was selected as more clear than usual, and as representing the general interpretation of the foliar arrangement on this aspect of the cerebellum ; I am not, however, satisfied In all respects, and regret that I cannot determine certain points upon my own preparations, so as to base the figures upon them entirely. These remarks apply equally to Fig. 697. 159 Brain. Brain. REFERENCE HANDBOOK OF THE MEDICAL SCIENCES. § 115. Peduncular Sulcus {^ great hwizontal Jissure"). — When the flocculus and paraflocculus are removed, or the overlapping foliums of the cerebellum are separated from them and from one another by the removal of the pia, the non-foliated lateral surface of the medipeduncle is easily seen to continue laterad and dorsad for about 1 cm. between the tiers of foliums on the cephalic and the caudal aspects. This interval is the beginning or stem of what is commonly called the " great horizontal fissure," but which, from its obvious relation to the medipeduncle, I have called peduncular. By most writers it is repre- sented as continuing along the dorsal (" posterior ") mar- gin of the cerebellum and as demarcating the cephalic and caudal aspects of "the entire organ. In particular it is regarded as meeting its opposite at the meson just caudad of the cacumen, a single thin folium which, at either side of the meson, enlarges and becomes a subdi- vided cacuminal (" presemilunar ") lobe. § 116. TTie Peduncular Sulcus Incomplete as a Land- ma/rk. — But, while it is perfectly possible, with most postgeminum- medipedunelei -\- Poirs. euhninal s. furcal sulcus. medipedunole.— vsuauniiuills.- Jhooi^t fteeexltr i.~ epiplexus pyramidal s.--^ uvular «.- B. B. Stroud, del Fig. 701.— Dia^fram ShowinK the Divisions of tbe Human Cerebellum as If Extended in One Plane. (From Stroud, 1897, b, 108. ) The line between the cacuminal lobe and the tu- beral lobe should be designated peduncular sulcus ("horizontaUs magnus "). specimens, to recognize a deep sulcus of the pileum which passes caudad of the cacumen and trends laterad in the direction of the medipeduncle, an inspection of the depths arouses doubts of its essential continuity and morpho- logical significance. § 117. Mircal Sulcus. — On various grounds, especially comparative anatomy and development, Stroud has con- cluded (1897, a, 6) that the primary and most constant sulcus, and the one which should be held to demarcate the two main regions of the cerebellum, is one which leaves the stem of the peduncular sulcus opposite the at- tachment of the paraflocculus and passes at right angles across the cephalic surface, dipping between the ad- jacent foliums so deeply as to more nearly reach the cavity than any other of the sulci. As seen in Table III. the furcal is the preclival sulcus of Schafer. § 118. The region cephalad of the furcal sulcus is divided by the culminal sulcus (postcentral of Schafer) into the culminal lobe and the central lobe. § 119. lAngula. —Wlxea the central lobe is lifted or removed there will be exposed the valvula, the thin zone of the mesocelian roof, and caudad of it, completely overhung and concealed by the adjacent parts of the cerebellum, a series of three, four, or five transverse di- minutive foliums; see the medisection (Fig. 703). At birth the lingular folia are rounded and distinct, but in the adult they are relatively smaller, often flattened as if by pressure of the overhanging cere- bellum, and sometimes (at least in cer- tain negro and insane brains) nearly or completely absent.* The cephalic foli- um is narrowest and has a rounded outline (Fig. 700): the pia adheres quite firmly to these folia, so that they are liable to be torn off. § 120. Fig. 70S illustrates: A. The mesal topography of the cerebellum and adjacent parts when brought into nearly their "normal position," i.e., when the metepencephalic floor is nearly horizontal (cephalo-caudal) and when the longer axis of the cerebellum is nearly dorso-ventral ; this is nearly their condition in a body lying prone, with the axon and longer portion of the neuron (myel) approximately hor- izontal, as with most quadrupeds and the majority of walking and swim- ming vertebrates (see § 9, and the arti- cle on Termiriology, AiMtomicaV). For comparison with Figs. 670, 687, and 756, this or they must be regarded as turned about one-fourth of a circle. B. The exact number and form of the cerebellar folia and subfolia at birth, so far as they appear upon an approximate medisection. C. The combination of the folia to form lobes, more or less well defined. D. The arboriform arrangement, whence the name a/rbor vitce (herein mononymized to a/rhor). E. The topographical relations of the mesal lobe (vermis) to the lateral lobes ; caudad, dorsad, and at the ven- tro-cephalic region the lateral lobes project beyond the vermis, but the latter is the more prominent with the culmeil at the cephalic side and with the nodulus at the caudo - ventral angle. The interval between the lat- eral lobes on the caudal aspect consti- tutes the vallis. F. The enormous size of the cere- bellum as compared with its cavity, even had the dorsal part of the latter been maintained at its natural size by alinjection. G. The projection of the cerebellum beyond its attach- ments and proper cavity. Cephalad, it overhangs not only the valvula, but the postgeminum, these being parts of the mesencephal ; caudad, whatever exact limit be as- * The lingula has not been recognized in the apes, but Stroud is in- clined to regard as Its homologue what he described (1897, 7), 120) as a "cephalic " lobe in apes and in certain human brains, e.g.. Fig. 698. 160 REFERENCE HANDBOOK OF THE MEDICAL SCIENCES. Brain. Brain, cacuminal lobe cllvus - furcal sulcus — — furcal sulcus culmen central lobe ~ signed to the epicele, the vermis covers the entire "fourth ventri- cle." H. The distinctness of the four lingular folia, constituting the transition from the massive cerebellum to the atrophic (?) val- vula. I. The prominence of the cephalic and caudal margins of the pons, and the concomi- tant depth of the pre- pontile and postpontile recesses. J. The merging of the dorsal commissure of the myel and post- oblongata into the obex, and of this into theligula; in the adult this latter seems to be hardly more than the combined pia and en- dyma (see Fig. 693), but in the child's brain from which this fea- ture was derived, al- though the meninges had been removed, there was, neverthe- less, a distinct lamina of nervous substance. § 131. The divisions of the caudal region of the cerebellum can- not be seen complete- ly unless the post- oblongata is forcibly bent ventrad or cut away; indeed the en- tire oblongata and pons may advantageously be removed by tran- section of the pedun- cles ventrad of the floc- culi as in Fig. 697. § 133. When the pil- eums are divaricated the postvermis caudad of the cacumen is seen to be at first narrow, then wider, and then decidedly compressed. The wide portion is thepyramis; the short region between it and the cacumen, the tuber ; the longer portion of the remainder is the uvula crowded between subglobular divisions of the pileums, the tonsils. Fi- nally, and seen with some difficulty, is the nodulus, a group' of three or four f oliums, connected at either side by the kilos with the flocculus. The relations of these parts to one another and to the lateral masses and to the sulci are indicated upon Table IV. • Table III.— Stnontms op the PEiiJon>AL Sulci op the Oeke- BELLUM ; STROUD, 1897, a. Scbafer. 1. Sulcus precentralis. 2. Sulcus postcentralis. . 3. Sulcus preclivalis. i. Sulcus postcliralls. 5. Sulcus borizontalis magnus. a. Sulcus postgraciUs. b. Sulcus intragracills. 6. Sulcus pregracllis. I s. postpyramidalls. f 7. Sulcus prepyramldaUs. 8. Sulcus postnodularis. peduncular sulcus uiilal sulcus - — — pyramls pyramis pyramis myelocele Fio. 702.— The Metepencephal (Cerebellum, Oblongata, and Pons) of a Child at Term, Showing the Approxi- mately Mesal Aspect of the Right Half; 478. X3. Traced from an enlarged pbotngrapb. (This Is the same specimen that is shown in Fig. 756, where, however, no attempt was made to represent details, and the cerebellum is more nearly in its " natural attitude." 1, Prepontile recess ; 2, postpontile recess (fora- men cceeum) ; 3, presumed caudal end of the pyramid ; between 3 and 4 there might be— but were not seen— indications of the pyramid decussation (Figs. 672 and 689) ; 5, slight elevation of the metaoelian floor ; the triangular darker area Just ventro-cephalad represents the posttovea ; 6, the dorsal extension of the epi- cele into the cerebellum ; ^, metatela (dia{;;rammatic). Defects. —The plane of section passed slightly sinistrad of the meson ; hence certain features are not exsMitly what would have appeared iipon a precise medlsection. On the cut (unshaded) surfaces the alba and dnerea are not distinguished, the latter having been bleacbed by the alcohol. The pons section does not show the fibres of the raph^. The cavities were not allnjected and hence are unnaturally small. The meninges were removed ; so there is no indication of the dorsal attachment of the arachnoid to limit the subarachnoid space, and the obex, Ugula, and metatela are supplied from other specimens, but the extent of the metapore (foramen of Magendie) is not shown. When the drawing was made, the significance of the furcal sulcus had not been recognized. Dr. Stroud has kindly revised the identifications. He would limit the prevermls to so much as is cephalad of the fur- cal sulcus ; but for the present 1 retain the original designations of the two regions of the vermis. The sul- cus just cephalad of the cacumen Is the cacuminal ; that Just caudad is the peduncular, deep in the pileum (lateral lobe) but shallow at the meson. The tuber is the part between the peduncular and tuberal sulci. See § 120. Table IV.— Synonyms of the Lobes op the Cerebellum; Stroud, 1897, a. Slightly Modified. Preferred. 1. Central sulcus. 2. Culminal sulcus. 3. Furcal suleus. 4. Cacuminal sulcus. 5. Peduncular sulcus. 6. Pyramidal sulcus. 7. Uvular sulcus. 8. Nodular sulcus. Vol. n.— 11 Terms Preferred. SCHAPER. Various Authors. Vermis. Vermis and pileum. Worm and hemi- sphere. Hemisphere. 1. (Lingu- la?),Ceph- alic lobe, variable 2. Central lobe. 3. Culmen.. Furcal sul- cus. 4. Cllvus . . . 1. Lingular lobe.. 2. Central lobe . . . 3. Culmlnal lobe . 4. Clival lobe Lobus llngulae 1. Lobus centralis.. 2. JVnt recognized as a distinct lobe. 3. Lobus culminls . . 4. Lobus cllvl Frsenulum llng- ulae. Ala lobull cen- tralis. Lobus lunatus an- terior. Lobus lunatus posterior. 161 Brain. Brain. REFERENCE HANDBOOK OP THE MEDICAL SCIENCES. Table IV.— Synonyms of the Lobes op the Cerebellum; Stroud, 1897, a. Slightly Modified.— OomtmMed. Terms Preferred. SCHAPBR. Various Authors. Vermis Worm and hemi- Vermis. and pileum. sphere. Hemisphere. 5. Cacumen 5. Cacuminal lobe 5. Lobus cacuminis. Lobus postero-su- perior. Presemilunar lobe. 6. Tuber . . . 6. Tuberallohe... 6. Lobus tuberis.... Postsemilunar lobe. Lobus postero-in- lerlor. a. pretuberal lobe. a L semilunaris inferior. h. medltuberal b Slender lobe. lobe. L. gracilis pos- terior. c. posttuhera] c. L. gracilis ante- lobe. rior. 7. Pyramis.. 7. Pyramidal lobe. 7. Lobus pyramidis. Cuneiform lobe. L. biventralis. Tonsilla. 8. Uvula.... 8. Uvular lobe.... 8. Lobus uvulae Amygdala. 9. Nodulus . 9. T h e nodulus does not ex- tend laterad into the pil- eum. The flocculus is a separate di- vision. It Is not a part of the pileura (or hemisphere) . 9. Lobus nodull Flocculus. § 123. Fig. 703 illustrates : A. The constitution of the dentatum as a corrugated capsule of cinerea, open cephalo- ventrad. B. The entrance of the fibres of the prepeduncle through the hilum of the dentatum to connect with its cells. § 134. Entocinerca. — Upon a medisection of the organ there would appear to be only alba and ectocinerea, the epicele -*- — ^v- nodulus ■ ;i.^,iSiii*L postpeduncle Fig. 703.— The Dentatums and Prepeduncles. (From Stilling, somewhat modified.) X2— . Pfeparaf M))i.— The plane of section was oblique, so as to coincide with the general direction of the prepeduncles as shown in Figs. 692 and 693. Defects.— By an inexcusable oversight the prepeduncles are not indicated by a line and the name ; but they are readily recognized as the fibrous tracts at the sides of the epi- cele. converging from the dentatums to the gemlnum. There Is no representation of the " fleece," the layer of fibres radiating from the ectal surface of the dentatum. former branching in a tree-like manner, whence the name arbor (vitce). But in the central part of the cerebellum, near the apex of the epicele, are four pairs of masses of cinerea sometimes called roof -nuclei or tectal nidi . There are reasons for thinking that the primitive cerebellar ento- cinerea has been displaced, and is represented by these masses enumerated in their order from the meson laterad ; Pastigatum; globulus; embolus; dentatum. § 125. The Dentatum.— This, is the largest and most easily recognized of the four masses ; (see Figs. 703 and 704). It has the form of a corrugated capsule, open lingula ■ commissure embolus globulus fastigatum dentatum PIG. 704.— The Dentatum and Other Masses of Cinerea in the Central Part of the Cerebellum. From Stilling, somewhat modified. X 2 - . Preparation.— This is commonly designated as a ' horizontal section. Keally, the plane cannot be indicated in such simple terms. The central part of the figure, including the cinereal masses, is through the f astigium, the roof of the apex of the epicele. jDe^ct'!.- No attempt has been made to represent the fibrous con- stitution beyond the purely diagrammatic indication of the cephaUc (anterior) decussating commissure. meso-ventro-cephalad, for the reception of the fibres of the prepeduncle (Fig. 703). In any cerebellum, whether fresh, or hardened in chromic acid compounds, or even alcohol, it is readily recognized upon transections or upon sagittal sections begun about 1 cm. either side of ' the meson and continued laterad for 3 or 3 cm. The dentatum has received the following additional names, of which the last only is used with any frequency: Nucleus dentatus ; corpus denticulatum, s. fimbriatum, s. lenticulatum, s. eiliare ; Eng. , ciliary body. § 136. The Pastigatum.— Thia, more often called "fastigial nucleus," is close to the meson, directly in the roof (fastigium) of the epicele; Fig. 703. It is rounded cephalad, but the caudal end presents two or three projections. § 127. The Embolus and Globulus. — These smaller masses of cinerea lie between the dentatum and the fas- tigium, and somewhat dorsad of the latter. Their forms are indicated by their names, and are well shown in Stilling's figure as reproduced in Fig. 704. More common (and cum- bersome) titles are nucleus globosus or glohuliformis, and nucleus emboli- formis. • § 138. Fig. 704. illustrates : A. The existence, near the apex of the epi- cele, of four pair of cinereal masses, representing, perhaps, dislocated por- tions of the cerebellar entocinerca. B. The lack of precise symmetry in the forms of these masses ; of the globuli there are three on the left and two on the right, the more cephalic probably representing two. V. Mesbncephal. — § 129. Syn- onyms: Mesencephalon; midbrain. Tabular arrangement of parts: Chief parts: quadrigemlnum and crura. Cavity: mesocele (aqueduct or iter.) Floor: crura. Sides: gemina. Roof: gemina and valvula. Ectocinerea: cappa. Entocinerca (" central tubular gray "). Commissures : postcommis- sure, trochlear decussation. § 130. In early embryonic stages the mesencephal is the most conspicuous region of the entire brain, but con- gemmum semicircular fibres globuli cinerea of the dentatum fibres of the dentatum rimula 162 REFERENCE HANDBOOK OF THE MEDICAL SCIENCES. Brain. Brain. sists of a single, thin-walled vesicle, with a relatively large cavity (Figs. 671 and 677). As the parietes thicken, two fuiTows appear upon the dorsal aspect; a mesal, demarcating the left elevation from the right, and a transverse, subdividing each of these into a cephalic and a, caudal portion (Fig. 673) ; there results, in the adult mammalian brain, the formation of four approximately similar elevations, whence the names, corpus quadri- geminum, corpora quadrigemina, optic lobes, etc. In the present article they are called gemina (twin bodies), pre- geminum and postgeminum (Figs. 693 and 707). They constitute the larger part of the mesocelian roof. § 131. Valtula. — k. caudal portion of the mesocelian roof retains nearly its primitive tenuity as a transparent lamina, the valvula, between the gemina and the lingula (Fig. 703). Its cephalic part presents some slight corru- giations, either a mesal furrow and a pair of lateral ridges, the frenulums (Fig. 706), or a mesal ridge in addition. § 133. The fibres of the trochlearis nerve decussate in the valvula. It is practically convenient, although not perliaps quite correct, to regard the trochlear decussa- tion as the boundary between the mesocelian valvula and the epicelian lingula (see Fig. 675). § 133. Mesocele. — In all mammals what Tiedemann picturesquely described as a " vast and spacious cavity " becomes relatively' an insignificant tubular passage, which has been called " aqueduct " and iter a tertio ad quartum ventrieulum. As may be seen from Figs. 670, 687 and 7.'56, it is expanded or trumpet-shaped at the cephalic end, and irregular in form at the caudal ; the intermedi- ate, longer part varies considerably in different indi- viduals, being sometimes nearly cylindrical, but usually a transection presents points in two, three, or four direc- tions, lateral, ventral, dorsal; the departures from the cylindrical shape are more frequent and distinct in the postgeminal and valvular portion (see Figs. 687, 706, and 708), and may be regarded as vestiges or suggestions of the potentially tripartite condition which is actually pres- ent with birds and frogs (Fig. 685). § 134. Lemniscus and Brachia. — The lateral slope of the mesencephal presents three megascopic features, the lemniscus, postbrachium, and prebrachium, shown in Fig. 706; in the former the fibres run approximately cephalo-dorsad, in the latter obliquely dorso-ventrad ; their course and con- nections , are considered in the article Brain, -.Ristologt/ of the, as is also the extent of the ectociner^l lamina called cappa. The lemhiscus and its connec- tions have been discussed at consider- able length by E. C. Spitzka, 1884, c. § 135. Entoeinerea. — This is the least modified of all portions of the ence- phalic " central tubular gray " ; it forms a layer 3 to 8 mm. thick surrounding the mesocele. § 136. The Crura (onira or pedunculi cerebri). — Excepting the parts already named, the mesencephal consists mainly of a pair of fibrous masses (Figs. 673 and 689) containing the compacted mo- tor and sensory conductors between the regions caudad, whose relations are mainly, with the body, and the regions cephalad,.jivhich are the organs of the mind. Each crus consists of two re- gions, a ventral, the crusta, and a dor- sal, the tegmentum (Figs. 706 and 708). § 137. Intercalatum (substantia ni- gra, locus niger). — A transection through the crus at almost any level reveals a dark mass (Figs. 706 and 708) of crescentic outline, approximately dividing the section into a ventral third and a dorsal two-thirds. Its lateral and mesal borders correspond to the furrows called sulcus lateralis and *. oculomotorius. The name commonly employed refers to the distinctly dark color (due to pigment in the cells) of the mass in man and some apes ; but the absence of color in other mammals has led E. C. Spitzka to propose a name referring to its more constant character of intercalation between the ventral crusta and the dorsal tegmentum ; the locative mononym was adopted by the Association of American Anatomists in 1897. § 138. Postcommissure. — The cephalic margin of the mesocelian roof is of moderate thickness, and curved epiphysis supracommissure epiphyseal recess postcommissure 4- mesocele tegmentum intercalatum crusta Fig. 705.— The Postcommissure and Adjacent Parts ; 2,239. X 1.5. Prepcwation.— The diencephal was transected just cephalad of the postcommissure ; the diatela was torn away to admit more light ; the space just above the epiphysis was occupied by the dorsal sack. The figure should be compared with the medisections (Figs..670 and 687), and with the dorsal aspect of the region (Figs. 707 and 708). / dorsad so sharply as to present a cephalic convexity (E^g. 705) and a caudal concavity (Fig.- 687). Osbom has suggested that it is intersegmental like the trochlear de- cussation (Fig. 675). § 139. Fig. 70S illustrates : A. The appearance of this aspect of the postcommissure as a cylinder. B. The considerable size of the epiphyseal recess ; al- though a mere diverticulum within an apparently func- tionless organ, it is larger than the cephalic orifice of the mesocele in this specimen. C. The distinctness of the supracommissure (commia- sura habenarum). prebrachium postbrachium | caudatiim pregemmum I postgeminum frenulum I valvula I I aqueduct po I Pig. 706.— Caudal Aspect of the Mesencephal and Part of the Diencephal : 2,360. X 1.5. 1, Tenial sulcus ; 2, right postgeniculum ; 3, right pregeniculum. Preparation.— A well-hardened, alcoholic, adult brain was transected just cephalad of the pons, at a level indicated nearly by the line from cms in Fig. 707. A block containing the thalami and adjacent parts was then cut out by incisions i&t various directions, the fornix peele(Pofl, and the velum and other parts of the pia rem'oved ; the ink lines near the sides marked ripa indicate the lines along which the lateral margins o( the velum, the paraplexuses, were torn ■away. De/ects.— More should have been left at the sides and ventrad. On the left, the roughly indicated curved line just laterad of the tenia was due to inadvertence, and may be disregarded. See § 140. D. The location of the dorsal sac upon (morphologi- cally, cephalad of) the epiphysis: see Fig. 687. E. The modified relative position of these parts. In a less modified condition of things, the two commissures and the epiphysis should all lie nearly in one plane ; but the pressure of the superincumbent cerebrum has made 163 Brain. Brain. REFERENCE HANDBOOK OF THE MEDICAL SCIENCES. the long axis of the epiphysis cephalo-caudal instead of dorsG-ventral, and left the two commissures and the two oriflces in a dorso-ventral series instead of a cephalo- caudal. § 140. Mg. 706 illustrates : A. Segmental overlapping. The thalami and geniculums project caudad beyond the intersegmental line, and the caudatum is here directly laterad of the thalamus instead of cephalad ; consequently a transection through the pregeminum would divide not only the mesencephal, but also both the diencephal and the prosencephal. B. The caudal extension of the thalamus as a rounded eminence, the pulvinar, on which, at the right, the word thalamus is placed. C. The existence of two other eminences on this aspect of the diencephal, the postgeniculum, mesad and more distinct, and the pregeniculum, laterad and less distinct. With lower mammals the general mass of the thalamus is less developed than in man, and the pregeniculum is not only still less prominent, but also decidedly cephalad, so that the prefixes pre and post are much more appro- priate. D. The continuity of the optic tract with both the geniculums, more obviously with the pregeniculum. E. The nearly complete concealment of the pregemi- num, in this view of the parts, by the postgeminum ; the former is seen at the left to project slightly. F. The location and forms of the postbrachium and prebrachium ; the former is between the two geminums, the latter just cephalad of the pregeminum ; as they pass ventrad they embrace, as it were, the postgeniculum. Q-. The location of the lemniscus, just caudad of the postbrachium. H. The T-shape of the mesocele in this specimen. I. The thinness of the mesocelian roof, here constituted by the valvula, with a mesal furrow and lateral ridges, the frenulums. J. The relatively extreme thickness of the mesocelian floor, constituted by the crura. K. The division of each crus into a ventral crusta and a dorsal tegmentum, the boundary between these two regions being defined partly by the lateral furrow, op- posite the word crus, on the left, and partly by a pig- mented tract, the intercalatum, not here seen, but shown in Figs. 705 and 708. L. The deep ventral depression between the crura, constituting an intercrural area. M. The presence, at the cephalic end of this area, of several rather large foramina for the transmission of arterial branches, whence this part is called postcribrum ("posterior perforated space "). N. The trefoil outline of the mesencephalic transection due to the mesal and the two lateral depressions. O. The obviously and unquestionably pial and ecto- celian character of all the natural mesocelian surfaces. P. The equally unquestionable continuity of these sur- faces over the geniculums to the pulvinar. Q. The absence of anything like a ripa on the visible surface of the thalamus until we reach the sharp and irregular line so marked at the left. R. The endymal and entocelian character of the slender natural surface of the caudatum. S. The continuation of this endymal surface upon the visible length of the tenia. T. The significance of the ripa as not only a boundary between contiguous pial and endymal surfaces, but as indicating where the margin of the paraplexus or some membranous continuation of it has been torn away. § 141. Mg. 707 illustrates : A. The segmental overlap- ping of the diencephal at the side of the mesencephal and of the prosencephal at the side of that (see § 55). B. The division of the caudatum (the entocelian por- tion of the striatum) into a cephalic, enlarged caput and a caudal, slender canida. C. The unlike topographical relations of these two parts," in that the caput is uncomplicated, while the Cauda has a slender, marginal (riparian) band at its mesal side, the tenia, having peculiar relations with other parts. D. The location of thediacele between the two thalami and its continuity with the aula. E. The presence of the medicommissure (seen somewhat better in Fig. 709). F. The relation of the callosal genu to the intercerebral Assure and the pseudocele; but for the callosum the Pig. tot.— Dorsal Surfaces ol the Caudatum, Thalamus, and Gemina. (From Henle, reduced and slightly modified.) 1, Tenlal sulcus ; 8, flmbrial sulcus ; 3, habenal sulcus ; 4, trigonum ; 5, " anterior tu- hercle" of the thalamus. Preporatiora.— The dorsal portion of the cerebrum has been re- moved, including the callosum, fornix, velum, paraplexuses, and diatela; also the pia covering the epiphysis! and mesencephal. De/ecfs.— The shading Is too deep and does not indicate the dis- tinction between the pial and the endymal surfaces. The caudal parts of the thalami are crowded mesad, and the gemina are not . well shaped. fissure and the pseudocele would be continuous, as would also the hemiseptum with the general mesal wall of the precornu. G. The demarcation of the mesal, entocelian surface of the thalamus from the dorsal, entocelian surface by a rough edge just dorsad of the habena ; here it is repre- sented by the narrow, white line between the two black ones, and designated as the habena; it is really a ripa along the dorsal side of the habena (see also Figs. 687 and 739). H. The presence of three shallow furrows on the dor- sal surface of the thalamus ; a dorso-mesal, just dorsad of the habena, the habenal sulcus ; a lateral, correspond- ing nearly with the mesal edge of the tenia, the tenial sulcus ; an intermediate and oblique, corresponding with the lateral margin of the fimbria (removed), the flmbrial sulcus. I. The demarcation of the dorsal surface of the thala- mus, which is pial and ectocelian, from the adjoining surface of the caudatum and tenia, which is endymal and entocelian, by a sharp, irregular line at the mesal edge of the tenia, constituting a ripa. This line was intro- auced into the figure ; it is absent in the original, as in all similar figures known to the writer, excepting Fig. 16, in Meynert's "Psychiatry," where it is called "linea aspera, " without, however, any reference to its morpho- logical significance. J. The vague and unsatisfactory representation of the parts at the porta. This region has yet to be cleared up in respect to the relation of the pial and endymal surfaces ; it was my inability to show these relations clearly upon original preparations that led me to employ the present figure provisionally. K. Incidentally it may be remarked that both this and 164 REFERENCE HANDBOOK OF THE MEDICAL SCIENCES. Brain. Brain. the previous figure exemplify the advantages of that feature of the simplified nomenclature which consists in the designation of members of natural or artificial groups of parts by words compounded of the generic terms and prefixes indicating relative position; e.g., pregeminum and postgeminum; pregeniculum and postgeniculum; precommissure, medicommissure, postcommissure, and supracommissure. V. DiENCEPHAL, — § 143. — Synonyms: Diencephalon, tleutencephalon, thalamencephalon, interbrain, 'tween- brain. Tabular arrangement of parts: Chief parts: thalami. Cavity: diacele. Floor: tuber, chiasma, and diaterma. Sides: thalami. Roof: diatela (practically the velum). Plexuses: diaplexuses. Commissures and decussations: medicommissure, supracommissure, chi- asma. Ectal elevations: albicantia, pregeniculums, and postgeniculums. Perforated areas: precribrums and postcribrum. Bntal elevations: habena. Ectal de- pressions: trigonum, habenal, tenial, and flmbrial sulci. Bntal depression : aulix (" sulcus of Monro"). Append- ages : hypophysis, epiphysis, and dorsal sac. With the adult of man and all other mammals the primitively thin sides of the diencephal are greatly thick- ened and become the ihala/mi, with the geniculums (pre- and post-) as latero-caudal elevations. The relations of the diencephal to the entire brain are well indicated in the young rabbit (Fig. 681). § 143. The pregeniculum and 'postgeniculum are repre- sented in Figs. 706 and 707, and described in connection therewith; the optic tract and the cMasma are shown in Figs. 689 and 711, and considered in connection with the optic nerves in the article. Cranial Nerwa. § 144. Mg. 708 illustrates: A. The form, direction, -- prehypophysis — optic n. - posthypopliysls — infundlbulum optic tract tuber albicans cms ■ K L- postcribrum —oculomotor nerrs crusta Intercalatum tegmentum . mesocele postgeminiun Fig. 708.— The Tuber (tuber cirwrevm) and Adjoining Parts ; T06. X 1.5. (The same region is shown In llgs. 672 and 689, upon a smaller scale.) 1, Expanded proximal end of the Infundlbulum, covering the lura, which is exposed In Hg. 672 ; 2, a slight elevation between the tuber and the optic tract. The Irregular line across , the tuber and optic tracts represents the cut or torn edge of the pla, which adheres quite flrmly to the chiasma. The black spots repre- sent the foramina In the postcribrum and elsewhere through which vessels passed ; the triangular region laterad of the chiasma is a part of the precribrum C" anterior perforated space "). Preparation..— The brain was removed with great care, the hy- pophysis being extricated from Its fossa by dividing the dural folds in several directions with the sharp point of a scalpel, and then in- troducing the blunt-pointed syrlngotome. Defects.— The natural surfaces of the crura should have presented a more fibrous appearance (somewhat as to Fig. 689), and another preservative than alcohol would have dUTerentfited the cinerea on the cut surface. The albicantia have perhaps the appearance of overhanging the postcribnim too far, but this Is more nearly correct than the usual representation, as. for example, in Figs. 672 and 689. The left Intercalatum should be shown more nearly like the right. and complete separation of the albicantia; they are usu- ally represented (as in Figs. 673 and 689) as hemispherical elevations; here they are seen to be elliptical in outline, their longer axes converging caudad, and the caudal ends overhanging the postcribrum; in the sheep (Fig. 794) and in mammals generally the albicantial sulcus is a shallow depression or wholly absent. B. That the hypophysis is wider than long, and con- sists of two parts, conveniently called prehypophysis and posthypQphysis ; the latter is the smaller and partly as it were let into an emargination of the former. C. The expanded base of the infundibulum (1). D. The raised, unnamed area (3) at either side of the tuber. E. The demarcation of the crusta from the tegmentum by the intercalatum. F. The slight, angular extensions of the mesocele, which sometimes is almost circular in outline. § 145. The diacelian floor is various in direction and composition. Beginning with the mesencephalic floor, the crura (Fig. 687), there is a marked decrease in thick- ness in the region of the postcribrum (which may really be common to the two segments), as well as a deflection of the floor ventrad; the albicantia (Figs. 673, 689, and 708) constitute lateral thickenings, and then the floor is re- duced to an atrophied lamina comparable with the val- vula; this, with the shorter, thin part just cephalad of the intervening and dependent hypophysis, constitutes the tuber {f.uber cinereum) and infundibulum. The fusion of the stems of the primitive optic vesicles to form the chiasma, and the fusion of this with the other- wise thin diacelian floor, confers upon the latter in this region considerable thickness and firmness, but this part is again succeeded by the atrophied terma (Figs. 687 and 711), strictly the diaterma, in distinction from the proso- terma dorsad of the precommissure. Although the dia- terma has a nearly dorso-ventral direction, it should properly be regarded as part of the floor, since the aula, the mesal division of the prosocele, is constructively ceph- alad of the diacele, although actually more nearly dorsad. § 146. Hypophysis (pituitary body or gland, Figs. 670, 687, and 708).— This has a twofold origin, viz., from the neuron (posthypophysis) and from the enteron (prehy- pophysis); see the article Brain, Development of. Herd- man thinks it may have been an ancestral sense organ (American Naturalist, 1888, p. 1137). At present, not- withstanding its constancy throughout the vertebrates, its function is still in doubt, but the not infrequent co- existence of acromegaly with lesion of the hypophysis merits careful consideration.* § 147. In marked contrast with the massive sides the diacelian roof is, for the most part, very thin, consisting apparently of the endyma only, closely attached to the ventral or diencephalic layer of the velum, from which are developed the parallel diaplexuses (Figs. 716 and 733) dependent at either side. Cephalad, the diatela is con- tinuous with the aulatela, or perhaps directly with the fornix dorsad of the aula and portas; caudad, it extends for some distance beyond the proper diencephalic bound- ary, is reflected ventrad upon the dorsal (properly cephalic) aspect of the epiphysis to constitute the dorsal sac, and is then continuous with the supracommissure, and the epiphysis itself (Fig. 687). § 148. Mg. 709 illustrates: A. The size, form, and connections of the medicommissure; it is relatively smaller than in other mammals (Fig. 688), and slightly constricted about its middle; if isolated it would have the form of a pulley -wheel with a shallow groove. B. The relations of the mesal aula to the portas and to the diacele (see § 163). C. The thinness of the lamina uniting the two halves (columns) of the fornix. This lamina must be regarded as the primitive prosocelian terma as high as the dorsal limits of the porta, and may, therefore, be called the * On this subject articles have been published by Woods Hutchinson in the New York Medical Journal for July, 1900. 165 Braiu. Bratn. REFERENCE HANDBOOK OF THE MEDICAL SCIENCES, § 149. Habena (habenula); (Fig. 687).— At the dorsal margin of the mesal surface is tlie habena, a slight ridge, with a dorsal convexity, extending from the porta to the supracommissure, which unites It with its opposite. pseudocele IiemisepDum I precomu caudatum ' ' endyma fornix porta Fig. 709.— The Medlcommissure and Adjacent Parts; 2032. X 1.3. (Compare Fig. 707, where some ot the same parts are shown on a smaller scale.) Preparation.— The brain was removed with care so as not to tear the medlcommissure, and alcohol was injected per luram so as to harden the parietes and keep them apart. The prefrontal lohes were then removed, thus opening the precomua and exposing the caudatums ; with these as guides the block containing the medicom- missure was safely isolated ; the thalami are cut away almost to the level ol the commissure. See § 148. Along the dorsal side of the habena is the habenal sul- cus, and the two represent nearly the line of reflection of the endyma from the mesal surface of the thalamus upon the roof of the diacele (see Figs. 681, 687, 707, and 732). § 150. Fig. 710 iUiistrates : A. The overlapping of the cerebrum upon the diencephal, so that the transection of one includes the other. B. The folding of the pia covering the now apposed dorsal surface of the thalami and the ventral surface of splenium pia velum genu rostrum callosum' fomi.\ Fig. 710.— Diagrams Illustrating the Relations of the Callosum, For- nix, and the Pseudocele, the Constitution of the Velum, and the Su- perposition of the Prosencephal. The upper flgure represents the mesal aspect of the right half of the schematic brain ; the lower, a transection of both right and left halves at the level indicated by the line A in the upper. In the lower flgure the thickening of the black line representing the fornix may indicate the hippocamp, but strictly it should be corrugated, presenting an ectal furrow— the hippocampal Assure. The relations of the fornix to the rest ot the parietes would also be more completely shown had the black line been interrupted a little laterad of the hippocamps. Defects.— The aula, the mesal part of the prosocele, is shown of equal size with the diacele, and on the same level ; this is not the case, so far as the writer is aware, with any vertebrate in which the callosum and fornix attain dimensions such as are indicated m the flgure (see Fig. 725) ; but so far as concerns the special objects of this flgure, the above inconsistency may be ignored. Unhke most ol the figures, the substantial nervous parietes are represented by the heavy black line, the pia and endyma by Ughter ones. the cerebrum so as to constitute the velum (see Fig. 733); but sfhce this flgure does not represent the lapping of the prosencephal upon the diencephal at the sides, or the formation of the rima and paraplexus, the pia of the two segments is continued independently around each. C. The theoretical constitution of the diacelian roof by (1) the possible, though not always actual, continua- tion of the thicker nervous material at tlie sides, (3) the lining endyma, (3) the covering pia, one or both layers according to the closeness of their adhesion. D. The relations of the callosum, fornix, and pseudo- cele; the two former represent two lines of extended junction between the apposed mesal surfaces of the hemicerebrums; they are continuous at the splenium and likewise in man at the cephalic end; the space thus circumscribed like the hollow of a partition is the pseu- docele or " fifth ventricle " ; it is really narrower, but the relations are as indicated. E. The general constitution of the fornix is more fully described in § 197. § 151. Medicommissure (commissura media, s. grisea, s. cinerea, s. mollis, s. thalamic fusion). — Primarily sepa- rate, the apposed, mesal surfaces of the thalami unite (at about the fifth month of gestation according to Mihalko- vics), giving rise to what is commonly called the "middle commissure " (Figs. 670. 687, 707, and 709). It is in a di- rect line between the porta and the aqueduct, consider- ably nearer the former, and just dorsad of the aulix. The shorter, dorso-ventral, diameter, is 4-5 mm. , the longer, cephalo-caudal, 6-7. It is relatively larger in all other mammals {e.g., sheep, Fig. 688); it is present in turtles (Fig. 680) but absent in birds and other immammalia. Its functions are experimentally unknown, but in a man and a cat lacking the callosum, it was larger than usual. § 153. AriomaUes of the Medicommissure. — It is said to be sometimes double. Among sixty-six brains Wenzel found it absent in ten. It is wanting in at least half a dozen of the (about two hundred) brains prepared or ex- amined by me with reference to it, amongst others in No. 3,334, Professor Oliver.* § 153. Aulix (sulcus of Monro; part of the interzonal sulcus?). — Most well-preserved brains present a more or less distinct furrow just ventrad of the medicommissure terminating ceplialad at the porta (" foramen of Monro ") and caudad near the postcommissure, sometimes in the mesocele and sometimes in tlie epiphyseal recess. It was figured and described by Reichert under the title " sul- cus Monroi, " for which I proposed (1884, c) the mononym aulix, a furrow (Figs. 675, 687). f § 154. Epiphysis (conarium, pineal body or gland ; Figs. 675, 687, 707).— Excepting the laneelet {Branchiostonia) every vertebrate likewise has this apparently useless or vestigial diverticulum of the diacelian roof. Max Flesch believes that it is associated with the temperature ap- paratus, but the number of forms in which has been traced a connection between it and a rudimentaiy mesal eye is so great as apparently to wari'ant the view that it is the remnant of a primitive mesal organ of vision; see the papers of Beraneck (1893,) Heckscher, Ritter (1891), and StudniCka (1899); Ritter also describes the relation of the epiphysis to a blood sinus in Phryiiosoma. § 155. Acervus (aeervulus cerebri). — The adult epiphy- sis frequently has embedded in'follicular cavities calcare- ous particles known by the above names, and as " brain- sand "; in the brain shown in Fig. 687, it was so abundant as to leave a considerable cavity when removed, but this unusual feature is not represented. * I venture to suggest that some of the reported cases may have been based upon inadequate evidence. Unless the brain is medi- sected while fresh, or prepared by the injection of a preservative into the arteries or the cavities, or both, the medicommissure commonly fails to be reached ; Its peculiar softness causes it to break easily : and the Imperfect preservation of the adjacent thalamic surfaces might lead to the non-recognition of the slight elevation indicating its exist- ence. If the specimen is allowed to dry slightly, and is then held so that the light is reflected from the smooth endymal surface of the thal- amus, then the presence of the remnant of the commissure will be in- dicated by the absence of such reflection from an area corresponding with its usual location. There are lew other parts of the brain where errors of observation are more hkely to occur. t His and others have applied the name "sulcus Monroi " to an al- leged sulcus extending from the mesocele to or toward the optic recess, and have interpreted it as a portion of the interzonal sulcus (sttlctm limita/m ventriculorum) ; the grounds lor dissent from this Interpretation are stated in my papers 1896, d, and 1897, a. 166 REFERENCE HANDBOOK OP THE MEDICAL SCIENCES. Brain. Brain. § 156. Peculiar Topographic Relations of tlie Epiphysi». — One of the striking results of the segmental overlapping and crowding is the embedding, as it were, of the epiph- j^sis amongst four segments. Although directly con- nected with the thalami, the epiphysis leans caudad so as to rest upon the pregeminum; the cephalic aspect of the cerebellum rests upon the postgeminum and abuts against the epiphysis; finally the caUosum, a cerebral commissure, has its splenial curvature upon the epiphy- sis. Between all these parts, of course, there are mem- / e, " convolution of parietal eminence " ; PO, occipital Assure ; pp, postero-parletal convolution " ; K, central Assure ; g/, superfrontal gyre ; I, II, mesal transverse gyres, nearly at the level of tbe adjoining hemicere- brum ; in, sloping cortical suriface ; IV, mesal gyres at a lower level than I and II. Preparation. — The bram was taken from an epileptic imbecile, male, forty- eight years of age, 146.7 cm. (four feet ten inches) hiA, and weighing 55.7 kgm. (123 pounds). The entire brain weighed 1,111.7 gm. (39.35 ounces), of which the , cerebrum constituted 978 gm. (34.5 ounces) . Most unfortunately this rare, if not actually unique, specimen was simply placed in alcohol, which was not changed ; hence the base was in-preserved, and the ental features, although described in some detail by Turner, cannot be fully understood. A transection disclosed a single mesal, cerebral cavity, about 5 cm. wide, the floor of which is said to have been " formed of the upper surfaces of the corpora striata and optic thalami, which bodies were related to each other and to the twnia semieircuUvi'is as in a normal brain " : yet " the third ventricle opened freely into the cerebral cavity along the middle of the floor." It is to be hoped that figures and more detailed descriptions may be published respecting the structure of this remarkable specimen. A good abstract of the original paper is given in Brain, I., 133-134, April, 1878. nearly undivided. Substantially, the prosencephalic vesicle has not only increased in size and in parietal thickness, with but slight differentiation into a mesal and lateral mass, but the entire mass has developed fissures and gyres after the usual pattern, in general, ex- cepting that certain gyres cross the meson; a priori, in- deed, it is not clear why such a brain should not he eflS- cient for mental as well as bodily manifestations. * On this account it is to be the more regretted that so few such specimens are adequately preserved, examined, figured, described, and explained ; Indeed, no case is known to me in which the best possible use has been made of the opportunity ; it is particularly de- sirable that, when malformation Is suspected, the brain be thoroughly hardened by altnjection (Injection of alcohol) of both the arteries and the cavities. Fig. 714.— Diagram of the Prosocele and Adjoining Cavities. all the fissural corrugations and inequal- ities, excepting the Sylvian, which is a mere shallow depression extending obliquely dorso-caudad along the lateral aspect of each hemicerebrum. C. The enormous size of the porta, yet the maintenance of its complete circum- scription. D. The tenuity of most of the parietes; in the occipital region they are no thicker than a sheet of ordinary paper, and are really exaggerated by the two ink lines and inter- vening space. E. The extraordinary distinctness of the mass named coMdatum, of which another view is given in Fig. 723. F. The peculiar form and relations of the rounded mass intervening between the cau- datum and the lateral wall, and which may represent the lenticula. G. The non-appearance of the thalamus in the floor of the paracele. H. Upotf the whole, the retention, sub stantially, of a condition of the cerebrum comparable with the normal state at a much earlier period of development; it is, as it were, an ex- pansion of such a cerebrum as exists at twelve weeks (see Fig. 667). § 165. P(Wflsc«Zes ("lateral ventricles").— But the lateral extensions speedily become so considerable as to warrant the specification of a mesal portion, aula, a pair of pa/ra- celes ("lateral ventricles"), and constricted communica- tions, the portas ("foramina of Monro") (see Figs. 678, 684, 690, 723).* § 166. Gornua. — Each paracele is primarily sub- spherical and simple as in Figs. 667 and 678; in hydro- * If the rhinencephal is regarded as a segment, the aula and portas must be regarded as pertaining in part to it. 168 REFERENCE HANDBOOK OF THE MEDICAL SCIENCES. Brain. Brain. cephalus this condition may be maintained approxi- mately till birth (Fig. 715^. But normally, by the unequal thickening of the parietes, by their encroachment upon the cavity, and perhaps by the further extension of the latter, there are somewhat vaguely demarcated a central eella, continuous through the pm'ia with the aiila, and caudatum 2 3 lentloula (?) porta ;_portiplexus -^^ iliiibria I hipIKJcamp (?) paraplexus Fig. 715.— The Left Paracele (Lateral Ventricle) of a Female New-Bom, (7 Months?) Hydrocephalus. No. 2,131. X' 1. 1, One of several slight undulations of the ental surface in the frontal region ; 2, slight pit, probably artificial ; 3, cephalic margin of a break, apparently natural, in the mesal parietes ; the ven- tral margin of this break is indicated by 7, and the corresponding caudal margin projects slightly mesad Just caudad of the line ; it may be supposed that this interruption of the mesal wall represents the loca- tion of the caUosum that might have been formed ; 4, 5, slight elevations as yet undetermined ; 6, dis- tinct though rounded ridge corresponding to the shallow Sylvian Assure, the only recognizable As- sure ; 7 (see 3) ; 8, occipital end of the hemicere- brum, projecting slightly beyond the cut surface ; 9, membranous portion of the parietes (perhaps an attenuated tenia) through which the thalamus shows. Preparation.— The child was supposed by the physician and parents to be seven months advanced ; it breathed a few times ; the weight was 1,618 gm. The neck and scalp were swollen, but the head was not unusually large. Normal salt solution was in- jected into the umbilical vein and escaped, with blood, from the Jugular. Then half a litre of ninety-per-cent. alcohol was injected, the Jugular being closed. The scalp, calva, and dura were re- moved, and the head supported in brine while the brain was extracted; in spite of care there was some separation of the hemlcerebrums at the me- son. The contained liquid was allowed to escape, the brain placed in ninety-per-cent. alcohol, and the hemlcerebrums iuAated to their natural size ; they were then covered Willi a thin layer of absor- bent cotton to keep them submerged. The alcohol was changed twice at intervals of two days, and on the Af th the various sections were made under al- cohol. The mass supposed to represent the caudatum was extremely dense. The pia was Arm, and in parts more substantial than the attenuated parietes. The condition of the dlenoephal was not fully de- terminable : the mesocele seemed to be wholly oc- cluded, which would account for the condition of the cerebrum. Th3 entire specimen needs further study and comparison with similar cases. three "horns," a ventral medicornu, a cephalic precornu, and a caudal postcornu. The last exists only in Primates (man, apes, monkeys, and lemurs) and a few other mam- mals, mostly members of the seal family. The cornua appear in Figs. 684, 730, 736, 735, and 736. § 167. Fig. 716 illustrates : A. The great extent of the paraceles at this period, relatively to the entire cere- brum, and to the mesal part of the prosocele, the aula. B. The less difference in the thickness of the parietes than in the adult. C. The distinct collocation of the hippocamp with the hippocampal fissure. D. The topographical relation of the Sylvian fossa, the first stage of the Sylvian fissure, to the caudatum. E. The extension of the postcornu farther caudad of the aula tlian the precornu extends cephalad. F. The absence of the insula at this period. G. The outgrowing margin of the operculum. H. The depth and peculiar shape of the lambdoidal fissure (see Fig. 750). § 168. The porta, in a little modified condition, may be seen in the large salamander, Cryptobranchus. When the lateral wall of the alinjected hemicerebrum is removed (Fig. 717), the paracele is seen to communicate with a mesal space (aula) and thereby with its opposite and with the diacele, through a considerable orifice, the porta. Its caudal end is narrower than the cephalic, but it is seen to be completely ciroumscribed by ordinary nervous walls. § 169. Mg. 717 illustrates : A. The simple condition of the prosencephal in this amphibian; each hemicere- brum is an elliptical, thin- walled sac, the cavity of which, the paracele, communicates through a porta with the aula and so with the diacele. B. The large size of the porta, its length equalling caudatum Sylvian fossa 1 : precornu ■ caudatum : : : genu precornu pseudocele hemiseptum supracommissure medicornu : 2 thalamus :■ paraplexus epiphysis Fig. 716.— Ventral Exposure of the Prosocele of a Fetus about 24 cm. Long, and Esti- mated to be Twenty Weeks Old ; 499. X 1.5. 1, Line of continuity of the thalamus and the caudatum ; 2, thin extension of the paraplexus into the postcornu ; soon after the preparation was made tliis became detached and was lost ; another speci- men must be depended upon to show whether or not such extension exists, and in what way it is disposed of in case it be deciduous ; 3, hippocampal Assure ; 4, dia- plexus. Preparation.— The brain was hardened in place by arterial aUnjection ; the scalp and calva were removed piecemeal, and the dorsal part of the cerebrum re- moved by one sweep of the knife under alcohol. The paraplexus was cut at each side as indicated by the heavy line (endyma) enclosing the lighter area. The left caudatum was removed so as to expose the paracele more completely on that side and make the Agure comparable with that of the cat (Fig. 686). 169 Brain. Brain. REFERENCE HANDBOOK OP THE IVIEDICAL SCIENCES. 3 porta Fir. 717.— Prosencephal ot Cryptobranchus (a Salamander), the Left Paracele Exposed ; 391. X 6. Preparation.— The fresh hraln, while supported by the skull, was alinjected by lifting the metatela (membranous roof of the "fourth ventricle") and pointing the cannula at the broad epieele ; the entire brain at once swelled somewhat, and the thinness of the walls caused it to harden almost Immediately ; the lateral wall of the left hemicerebrum was then sliced off, and the paraplexus cut off where it projected from the aula through the porta into the paracele. about one-third that of the entire cerebrum; its cephalo- caudal direction. as compared with that of mammals, birds,, and reptiles, where — especially in mammals — it is dorso-ventral. C. The absence of a rima; the prosoplexus enters the aula from the supraplexus and sends a prolongation through either porta into the paracele, where it hangs freely. § 170. The porta is com- pletely circumscribed, so that a cast has a definite outline, viz., that of an elongated el- lipse, its longer diameter, 4-6 mm. , its shorter 1-3 (see Figs. 718, 734). The portal bound- aries are as follows: caudal, the thalamus (perhaps the te- ,\^ paracele supraplexus dlencephal § 171. The exact conditions and relations of the rima, jjara- plexus" tenia, fimbria, and thal- amus near the porta have not been as yet clearly made out. Preparations should be made with special reference to then- elucidation, and figures upon a very large scale. Excepting the metapore ("foramen of Magen- die") no part of the brain in- volves so many and so important morphological questions; seethe difficulties and doubts admitted under Fig. 719. § 173. Fig. 719 illustrates : A. The size, form, and direction of the porta from the mesal as- pect. B. The complete circumscrip- tion of the porta, dorsad, by the reflection of the endyma upon the intruded plexus (Fig. 668). C. The greater length of that part of the prosoplexus which hangs in the porta (portiplexus) than of that which hangs in the aula (auliplexus). D. The constitution of the ve- lum as a fold of pia, with blood-vessels intervening; one lamina of the fold belongs to the fornix, and the other to the thalamus, or rather to the diatela or primitive dia- celian roof (Fig. 710). E. The relation of the ventral end of the porta to the aulix ("sulcus of Monro "). Fig. 718.— Cast of Aula, Portas, and Part of Dlacele. X 1.5. The main object of the flgure is to demonstrate the complete circumscription of the porta, and its independence of the rima(§177). The material used was a mixture of wax and gutta percha. The mesal ridge which represents the auUc recess is just dorsad of the precommissure (Fig. 734). The flg- ure should have been so placed as to make this ridge nearly vertical. nia); cephalic, the column of the fornix; ventral, the junc- tion of the thalamus and col- umn; dorsal, the endyma re- flected from the thalamus and column upon the intruded por- tiplexus (Pig. 668). So long as this endyma retains its ad- hesions, so' long the circum- scription of the porta is com- plete. auliplexus portiplexus medicommis8ur& lonncolumn porta dlacele precerebral a. — ^ * "- diaterma -i Fig. 719.- The Right Porta and Adjacent Parts, Seen Obliquely from the Caudal Side ; 385. X 4. The lateral aspect of the left porta of the same brain is shovra in Fig. 720, under which the mode of preparation is described. 1, Dotted line from the ventral end of the porta to the ventral margin ot the precommissure, and assumed to demarcate the diacele from the aula ; 2, part of the mesal sur- face of the hemiseptum, unusual and not fully understood (see 8 172, H). i3e/ecf8.— The area marked 2 is not a cut surface as its plainness would indicate ; it was shaded lightly in the drawing, but became blank in the engraving. The extent ot the pseudocele and the length ot the copula are so unusual as to be anomalous ; these peculiarities, however, do not materially affect the porta, which is the important feature ot the flgure. 170 REFERENCE HANDBOOK OP THE MEDICAL SCIENCES. Brain. Brain. F. The thinness of the commissure of the fornix, a. 6. The unusual length of the copula connecting the callosal rostrum with the prosoterma. H. The unusual extension of the pseudocele and of its lateral parietes, the hemiseptums; it is uncertain how far this existed naturally, or was produced by the pressure of alinjection. § 173. Fig. 7S0 illustrates : A. The location and general form of the paracele; unfortunately, however, the post- precomu porta Fig. 720.— The Left Paracele ("Lateral Ventricle "), Viewed Obliquely from the Latero-Ceplialic Aspect ; 385. X about ..5. (This figure was published in the New York Med. Jovr. for March 21, 1895, and Is here reproduced by permission.) Preparation.— The arteries and cavities were allnjected. When the brain was thoroughly hardened the medicornu was flrst exposed by removing successive slices of the temporal lobe till it was reached ; contiguous parts were then removed till the entire paracele was brought to view ; this involved the formation of Ave cut surfaces, all oblique excepting the most dorsal, which was about 1.5 cm. from the meson. The dura was retained until the preparation was com- plete and the drawing made ; it has since been medisected, so that the left porta may be looked through. cornu is unusually short, and foreshortened by the way in which the preparation is viewed; but the sharp curve of the medicornu is well seen, and the projection of the precornu cephalad from the porta. B. The absence of any indication of a rhinocele, which exists in the sheep (Fig. 793), and in mammals generally. C. The indis- tinctness of the col- liculi, calcar, collat- eral eminence, and occipital eminence; whether this was due to hydrocepha- lus or to the press- ure of the injected alcohol it is impos- sible to say. D. The location and size of the por- ta, which is shown on a larger scale in Fig. 731. E. The location FIG. 721.-The Left Porta and Adioining °^ JH PfJ^^Pleptus Parts of the Alinjeoted Brain Shown in and of the rima Fig. 720 ; 385. X 3. The form of the lat^ through which it eral or paracellan orifice of the porta ap- o„f j,™ r. mr <> r p H pears more distinctly, and the endyma is «"''''"'' ^" ,? ' seen clearly to be reflected upon the porU- however, by the en- plexus from the adjoining surfaces. Just dyma (Fig. 759). dorsad of the line from rima are a few c i rri jiVn 7Se (presumably) artificial rents In the en- .„» J-'^- ■^'*,' J,f djma. illustrates: A. The great size of the porta in this hydrencephal; its ventral half is concealed by the caudatum, but the total length (dorso-ventral dimension) is 19 mm. (three-fourths of an inch) and its width 8-9 mm. B. The complete circumscription of the porta, not- FiG. 722.— Lateral Aspect of the Right Caudatum and Porta (Foramen of Monro) of aNew-Born (seven months?) Hydrocephalus. 2131. X 1. 1, Angle between two cut edges of the thin mesal wall ; 2, cephalic end of the natural (although presumably abnormal) hiatus In the mesal wall, corresponding with 3 in Fig. 715 ; 3, ental surface of mesal wall ; t, depression between caudatum and ad.ioining pa- rietes ; 5, triangular depression near tip of medicornu ; 6, membra^ nous part of parietes ; see 9 3, G. Preparation.— See Fig. 715; the paraplexus on this side was trimmed closely. withstanding the delicacy of the parts and the pressure that may have caused its enlargement. C. The great extension of the paraplexus and adjoin- ing portions of the parietes; the parts marked 6 and 7 intercerebral f. FIG. 723.— The Two Portas, from the Precornua ; 2,345. X 1.5. 1. Part of the intercerebral fissure, between the rostrum dorsad and the chiasma ventrad ; 2, precornu ; 3, tenial vein ; 4, undetermined band on the cephalic slope of the thalamus ; 5, dorsal part of right paracele ; 6, the short diverging Unes point to the locations of veins (septal ?) at the angle of junction of the hemiseptums with the cal- losum ; dorsad of the junction of the hemiseptums with the ros- trum is a small (septal ?) vein at either side. Preparation.— See under Fig. 724. The slice including the portas is 12 mm. thick ; the caudal (aulio) aspect is shown in Fig. 724, the certialic (precomual) in this. Defects.— The shading does not indicate with sufficient distinct- ness that the entire surface, and plexus at either side dorsad of the porta, slope doreo-caudad beneath the callosum, and are not continu- ous with it. As in Figs. 724 and 739, the lines representing the cal- losal fibres are diagrammatic. Other preparations and figures upon a still larger scale are needed, in order to exhibit the somewhat in- tricate relations of the parts about the porta. The morphological importance of the entire aulic region can hardly be overestimated. are membranous; the zone justcaudad of 7, and forming part of the upper margin of the figure, may be the fimbria; and the thicker zone just caudad of it may be the hippocamp. § 175. Mg. 7SS illustrates : A. The existence of the two portas, and their obviously natural condition. This point, already shown in several previous figures, is here lYl Bralu. Brain. REFERENCE HANDBOOK OF THE MEDICAL SCIENCES, reiterated because this aspect of these orifices is seldom presented, and because a distinguished anatomist has de- clared (Progres Medical, Nos. 35 and 26, 1879) that when one finds a communication between the middle and lat- eral ventricles in an adult human brain it results from an artificial perforation; see my papers, 1884, a and 1884, /. B. The transection of the callosum in two places, viz., dorsad near the genu and ventrad through the rostrum; the part of the septum or pseudocele here shown was therefore embraced by the genual curve of the callosum (see Figs. 687 and 756). C. The continuity of the hemiseptum with the corre- sponding column of the fornix; so far as the porta is concerned, the former may be compared to a thin parti- tion, and the latter to a door-post ; see also Figs. 707 and 709. § 176. Mg. nil. illustrates: A. The existence, form, size, and complete circumscription of the two portas (" foramina of Monro "). B. The extent of the aula, the mesal- division of the prosocele, and the cephalic or prosocelian constituent of the "third ventricle." It includes the interval between the portas, extending ventrad so as to include the pre- commissure, only part of which appears in the figure. C. The existence of the aulic recess, a subtriangular depression between the precommissure and the two col- umns of the fornix; the line from the word aula ends in this recess; on the cast shown in Fig. 718, it is a ridge. D. The peculiar curvature of the columns of the fornix. They converge dorsad, curving at the same time caudad, Intercerebral f. ,,„„ callosal f. -*- callosum endyma roof of paracele hemiseptum pseudocele paraplexus ripa fornix velum aullplexus porta aula column precommissure tuber optic tract cMasma optic nerve Fig. 724.— The Two Portas, as Seen from the Aula, Looking Obliquely Dorso-Cephalad ; i!345. X 1.5. (Compare with Figs. 723 and 739.) 1, Tenial vein ; 2, velar vein ; the number rests upon the thalamus. Preparation.— From a brain, the arteries of which had been in- jected with the red glue mixture, and the cavities with alcohol, a transection was removed, 12 mm. thick, so as to include the chiasma ; for security of handling it was trimmed down so as to include little more than the parts represented. The optic nerves were divided obliquely, to show their cut ends more fully. Defmts. — The alba and cinerea are not distinguished, and the figure is not upon a scale large enough to show certain details as to the connections of the velum and plexuses. The divided ventral ends of the columns of the fornix were inadvertently omitted, but may be seen in Fig. 739. so as to appear as cut ends in this transection ; ventrad they diverge, are twisted somewhat, and again curve caudad, so that their cut ends should appear again just dorsad of the optic tracts, as shown in Fig. 739. E. The relation of the precommissure to the columns, which pass just caudad of it. In a figure including a greater width of this region, the cut ends of the precom- missure would appear at the side, as in Fig. 739. P. The refiection of the endyma upon the plexuses from the fornix and thalami, at two points upon each side; such lines of reflection constitute a ripa. G. The continuity of the hemiseptums with the cal- losum dorsad and the fornix ventrad. § 177. flima.— The porta is primary, and constant among all vertebrates where the prosocele presents a tripartite condition (§ 60). In reptiles, birds, and mam- precommis- sure terma. endyma parletes pla chiasma hypophysis Fig. 725.— Schematic Medlsection of the Prosencephal and Two Ad- joining Segments ; approximately the right halt of Fig. 7U, seen from the mesal aspect. (See § 178.) mals (perhaps also among some lower forms) at the dorsal end of the porta there begins a line of greater or less length along which the proper nervous parietes of the paracele are abrogated for the intrusion of a pial exten- sion, the paraplexus; this line of intrusion is the rima (chief part of the so-called "great transverse fissure") shown in Figs. 720, 725 (diagram), 730, and 735. It is to be noted that (1) the paraplexus fills the space, and (2) the endyma is carried before it, so that there is no true solution of continuity. The only way in which the porta and the rima can become continuous is by the arti- ficial rupture of the membranous attachment, but this is by no means infreCiuent with brains removed and handled in the usual way. § 178. Fig. 7S5 illustrates : A. The communication of the paracele (lateral ventricle) with the mesal series of encephalic cavities solely through the porta (" foramen of Monro "). B. The reduction in size of the aula, the mesal divi- sion of the prosocele, relatively to the diacele, and to the prosocelian lateral extensions, the paraceles. C. The location, in man and other mammals, of the aula at the dorso-cephalic side of the diacele, instead of directly cephalad as in Amphibia. D. The concomitant change in the direction of the dia- celian and prosocelian floors; instead of cephalo-caudal, their direction is more or less nearly dorso- ventral. E. The crowding of the epiphysis caudad by the over- lying cerebrum; the epiphysis and hypophysis are re- tained in the figure, however, mainly as landmarks. F. The relation of the rima (essential part of the " great transverse fissure ") to the porta. The line along the meso-ventral aspect of the hemicerebrum represents a narrow tract where the paracelian parietes are reduced to the lining endyma and the covering pia, and where the latter, or its vessels, intrudes into the paracele, still covered, however, by the endyma. The rima always begins at the margin of the porta, and extends, in man, to near the tip of the medicomu (see § 183 and Figs. 728 and 734). G. The secondary and morphologically unessential nature of the caudato-thalamic extension, the enormous thickening of the thalamus, the lateral wall of the diacele, and of the caudatum, the wall and floor of the paracele. This feature of the mammalian brain, which is very confusing and not altogether easy to describe, may be ignored in a diagram like the above, where the parietes are represented of nearly uniform thickness, as in the embryo and in adult amphibians. § 179. Fig. 726 illustrates : A. The close contact and even interdigitation of the mesal aspects of the frontal lobes of the sheep concomitantly with the absence of a falx. 112 REFERENCE HANDBOOK OP THE MEDICAL SCIENCES. Biraln. Brain. * PAKAPLEXUS paraplexus blppocamp __ -— i«a»— s;/- callosum HIPPOCAMP ^ splenium ,.__. MEDICOBND Fia. 726.— Sheep's Brain, the Paraceles ("Lateral Ventricles") Exposed. X 2. (From my " Physiol- ogy Practicums.") Prepa/ratton. — ^By the removal of successive slices the paraceles have heen opened ; the left has then been more completely exposed by oblique sections, and the paraplexus trimmed oil so as to expose the wide fimbria and the furrow between it and the hippocamp. The plane of section did not coincide exactly with the callosum ; the caudal three-fifths of this is represented by the transverse lines ; also the cephalic end, the genu ; but an Intermediate portion is wholly re- moved, exposing the narrow pseudocele ("flfth ventricle") and ita thin lateral walls, hemiaep- tums. Defects.— The cerebral cortex is not represented. The caudal half of the cerebellum is omitted. 1, Intercerebral Sssure ; 2, callosal fissure ; 3, vessel ; 4, interrupted lines indicating the con- tinuation of the paracele into the rhinocele (Fig. 792) ; 6, precomu ; 6, caput of the caudatum ; 7, Sylvian fissure crossed by arachnoid ; 8, vessel at bottom of fissure ; 9, cauda of caudatum ; ID, part of caudal wall of paracele. allow the plexal intrusion; at this age, therefore, the human thalamus is as perfectly ex- cluded from the paracele as it is in mammals generally. § 183. Paratela.— But with all liunian adults (perhaps also with the new -bom, and possi- bly with fetuses during the later months) the tenia and fimbria, for most of their length, are separated by an in- terval, 2-7 mm. in width, nar- rowing at the porta and in the medicornu. This interval is filled by (1) the paraplexus, which retains its attachment to the fimbria rather than to the tenia; (2) an extension of the endyma from the margin of the tenia with or without the adhesion of the subjacent pia. This zone of endyma, or endyma and pia, extending from the porta to near the end of the rima is the paratela (Pigs. 732, 735). § 183. Mg. 7S8 illustrates : A. The existence of substantial walls of nervous substance about the medicornu at the distance of at least 1 cm. from the tip of the temporal lobe. B. The concomitant rlon-ex- tension of the rima ("great transverse fissure ") to the ex- tremity of the medicornu. 0. The existence of digita- tions at the ventral end of the hippocamp (pes hippocampi). D. The non-extension of the hippocamp to the extremity of the medicornu. E. The dilatation of the medicoi'nu in hydrocephalus. P. The efiicacy of alinjec- tion in maintaining the size of B. The width of the fimbria and hippocamp, and thence of the entire fornix, as compared with the human. C. The apparent absence of the tenia. D. The total exclusion of the thalamus, even in ap- pearance, from the paracelian floor. § 180. Mg. 7^7 illustrates : A. That, at this age, the paraceles extend much farther dorsad than in the adult, far beyond the level of the callosum. B. That the paraplexus is relatively more ex- tensive. C. That the caudatum is relatively larger. D. That the margin of the fimbria reaches the groove between the caudatum and the thalamus, which probably represents the tenial sulcus of the adult. E. That the thalamus is therefore absolutely excluded from the paracelian floor, without even the appearance of representation which exists in the adult. § 181. With all mammals other than man, the apes and certain members of the seal family, the margins of the rima are, throughout their whole extent, separated only so far as to permit the in- trusion of the paraplexus, e.g., the sheep (Pig. 736); nor does this adhesion yield at all in cases of hydrocephalus, observed by me in dogs and cats. With the human fetus, also, up to the esti- mated age of four months (Pigs. 727 and 734), at least, the tenia and the fimbria are closely ap- -as closely, that is, as they can be and yet an encephalic cavity and pre- serving the contour of its parietes. G. The nearly typical zygal, or H-shape, of the orbital fissure (see Fig^ 778, III.). § 184. TJie Mima Not Coextensive with tile Medicornu. — The rima extends from the porta to near the extremity of the medicornu, but for about 1 cm. from its extremity callosum fornix .paracele paraplexus .caudatum 'tenial sulcus J medlcom- I missure thalamus diacele Fig. 727.— Transection of the Brain of a Fetus, About 16 cm. from Nates to Bregma, and Estimated at Four Months ; 1816. X 1.3. Preparation.— The fetus was received in alcohol, not very well preserved. The,calva was cut away with scissors, and the dura and pia removed. The entire brain was then transected at the level of the medicommissure, but only the dorsal half of the divided surface is included in the figure ; it is the ceph- alic aspect of the caudal part. The two lines crossing the right hemicerebrum indicate the plane of the section shown in Fig. 761. 1Y3 Brain, Brain. REFERENCE HANDBOOK OF THE MEDICAL SCIENCES. the parietes are substantial (Fig. 728). The transition to the rima is constituted by the riparian part, pala, which connects the two rimal margins, fimbria and tenia. This Tig. 728.— Ventral (Orbital) Aspect of the Right Fronto-Temporal Be- glon at the Hydrencephal Shown in Fig. 743, after removal of the tip of the temporal lobe ; 747. X 1. 1, Zygon of the orbital As- sure (see Fig. 778) ; 3, 3, 4, undeterminea Assures ; 5, undetermined Assure, zygal in form, perhaps the orblto-Jrontal ; 6, medltemporal (?) Assure ; 7, subtemporal (?) Assure ; 8, collateral Assure. Preparation. — See Fig. 743. thin portion has, in man, a shape like the blade of a turf- cutter; it is not distinctly shown in any of the figures in this article, but in Fig. 730 it would constitute the thin endyma Kg. 739.— Schematic Transections of the Medicomu at Four Different Levels. For simplicity the comu is represented as tubular and straiffht, normalized, so to speak (§ 38), and the parietes merely as substantial tissue covered by pia and lined by endyma. For some distance from its extremity (1-2 cm. in man) the medicomual pari- etes are typical, as at A ; this condition of the parts appears In Fig. 738. The proper nervous parietes suddenly become very thin and transparent, so as to resemble the terma and valvula, as at B. At C the proper nervous parietes have entirely disappeared, leaving only the two membranes ; this is the normal constitution of a tela, and sometimes exists near the tip of the medicornu, though relatively for a much less distance than on the diagram. Finally, whether or not a plexus is intruded into the cavity, as is the case with the medi- comu, the tearing away of the tela leaves a ragged edge which is a ripa at either side of the rima. lamella at the ventral end of the fimbria. In the diagram, Fig. 739, the pala is seen in transection at B. § 185. Fig. 730 illustrates : A. The early and distinct formation of the caudatum (see also Fig. 715). B. The continuity of the two margins of the rima, the fimbria and tenia, near the tip of the temporal lobe, the place of their union, at and after birth, being somewhat distinct, the pala. § 186. Fig. 731 illustrates: A. The thinness of the fornix at the meson (§ 203). B. The considerable extent of the pseudocele; smce this is not connected with the true encephalic cavities, it cannot be exaggerated by the hydrocephalous condition. C. The completeness of the pSraeelian floor after the removal of the thalamus; the interval, rima, between the substantial tenia and tlie lateral margin of the fornix (fimbria) is completely filled by the paraplexus and the paratela. D. The greater width of the rima in the cella than near the end of the medicornu. E. The extension of the calcarine fissure (stem of united occipital and calcarine) across the hippocampal gyre; it does not, however, reach the hippocampal fissure. § 187. Fig. 732 illustrates : A. The main point is the cpntinuityof the floor of theparacele ("lateral ventricle") irrespective of the dorsal surface of the thalamus, and the concomitant exclusion of this diencephalic mass from paracele caudatum tenia olfactory bulb temporal lobe Fig. 730.— Mesal Aspect of a Right Fetal Hemicerebrum, Partly Dis- sected ; 3,(X)0. X 2.5. 1, Transection surface between the caudatum and thalamus ; 2, part of cut surface left by removing a section of the mesal wall (including the rudimentary fornix and callosum) in order to expose the caudatum ; the paraplexus was also torn from its attachments, leaving the rima open ; its margins, the tenia and Ambria, are separated more than is natural ; in a fetus of this age they should be closely apposed (see § 181 and Fig. 737) ; 3, 4, transi- tory Assures in the places of the future occipital and calcarine. this portion of the prosencephalic cavity; but so many other points are shown incidentally that the figure will be described in detail. Beginning at the dorsal side of the figure, the inter- cerebral fissure is seen to separate the apposed mesal sur- faces of the hemicerebrums. The arachnoid dips into this fissure to a certain depth, so as to pass around the ventral margin of the falx (not shown in the figure); since this has (as seen in Fig. 801) a curved margin, and becomes narrower (dorso-ventrally) cephalad, the extent of the arachnoidal fold varies at different levels; in the specimen here figured, for example, which is about 1 cm. thick at the level of the callosum, the arachnoid crosses 5 mm. dorsad of the oallosum on the caudal aspect and 8 mm. on the cephalic. The pia, however, follows the ap- posed hemicerebral surfaces to and into the callosal fissure at either side and is continuous upon the dorsal surface of the callosum. Of the vessels the figure includes only the two parallel precerebral arteries (4). The callosum itself presents a slight mesal elevation, which is more dis- tinct at the cephalic side of the section and of a somewhat diiferent color (§ 217). The callosum extends laterad and likewise dorsad to form the roof of the paracele, and it is to be noted that the lateral portion of this cavity would be opened by a horizontal section at the level of the 174 REFERENCE HANDBOOK OF THE MEDICAL SCIENCES. Brain. Brain. Sylvian fissure dorsal surface of the callosum; hence the appearance commonly described and figured under the name of " centrum male majus " seldom if ever exists. For the condition of things in fetal brains, see Pig. 727, § 180. Ventrad of the callosum is the fornix, connected there- with by a thin lamina, the hemiseptum, at either side of a mesal cavity, the pseudocele. The lateral margin of the fornix is formed by the fimbria (corpus fimbriatum). At the extreme left of the figure the lateral wall of the paracele is seen to be formed by a cinereal mass, the caudatum. By reference to Figs. 707 and 735, it will be seen that this narrows rapidly from the cephalic end (caput) as a slender prolongation (cauda); but this Cauda is really folded somewhat upon its longitudinal axis so as to constitute, in at least part of its course, not only the side but a part of both the roof and floor of the para- cele; in the figures just mentioned the roof portion and part of the lateral is removed, leaving only the floor portion. Along the mesal border of the cauda there passes a vein (3), the tenial vein, which may be regarded as indicating the boundary between the cauda- tum and the thalamus. Projecting mesad of the vein is seen a lamina, consisting evidently of the paracelian endyma, and also, at least near the caudatum, of some nervous substance; this is, or in- cludes, the white band named tenia in this article, but commonly called taenia semieircu- laris or atria cornea. All the parts so far described are unques- tionably constituents of the prosencephal; the remaining portions shown in Fig. 733 belong to the diencephal. The walls of the diacele are the thalami, of which the figure includes only the portions dorsad of the level of the medi- and postcommissures (see Fig. 687). The mesal surface is covered by endyma, which is continued over the low ridge called habena (" habenula ") seen from the mesal as- pect in Fig. 687, and from the dorsal in Fig. 707. Just dorsad of the habena is a slight furrow, the habenal sulcus; here the endyma meets the pia covering the dorsal aspect of the thalamus, and is reflected with it dorsad and then mesad toward the opposite side. Instead of passing horizontally across the in- terval between the thalami, however, the en- dyma is deflected over the two vascular plex- uses (folds of pia or vessels therefrom) which hang in the diacele. The habena and its sulcus, more accurately, perhaps, the latter, constitute the boundary line between the mesal, entocelian, endymal surface of the thalamus, and the dorsal, ectocelian, and pial surface, which extends dorso-laterad. Between the dorsal surface of the thalamus and the ventral surface of the fornix (including, of course, the fimbria), the pia is freely separable, and appears to con- sist of but a single layer; but laterad it is traceable to the paraplexus, and it is almost inconceivable that a plexus should be formed of a single layer of pia as a free edge covered by endyma. When, however, this fornico-thal- amic pia is traced mesad, it is found to separate into two layers, a dorsal, belonging to the fornix, a ventral, con- stituting part of the diacelian roof (diatela) with a pair of arteries, a pair of veins, and numerous smaller vessels in the intervening space. The ventral layer is not separable (in man) from the diacelian endyma, but the dorsal not only may be detached from the fornix in an alcoholic specimen, as may the pia from most of the sur- faces which it covers, but here, excepting at the margins, the disjunction was almost spontaneous, and there is a distinct space (8) between it and the commissure, bounded at the sides by the thicker (hippocampal) con.stituents of the fornix. This double curtain of pia is the velum (interpositum), which belongs equally to the dience- phal and to the superposed prosencephal. Were it possible in separating the two segments, the dorsal layer should accompany the cerebrum, and the ven- tral remain attached to the thalami; the continuity of the two is seen at the aula and the two portas, as well endyma insula ,tenial vein itenia paraplexus attached to the paratela iparacele callosum .pseudocele hemiseptum ■fornix 3 2 splenium 1 hippocampal Assure ■dentate gyre ■calcarine Assure Ambria hippocamp medlcomu collateral Assure subtemporal Assure Fig. 731.— Transection of the Bight Hemicerebrum of an Adult Hydrocephalus ; 747. X 1. 1, Ventral curvature of splenium ; 2. groove at cephalic margin of splenium ; 3, mesal furrow of fornix (the line does not quite reach it). The furrow between the Unes from hippocampal iUssvre and dentate gyre is the continuation of the callosal Assure, separated from the hippocampal hy a Aattened area of cortex. The deep Assure opposite the word inmla is the central. Preparation.— This represents the cephalic aspect of the caudal part of the hemicerebrum, the mesal aspect of which is shown In Fig. 743. The transection was along the oblique line d-u on that Agure. So much of the thalamus as was included was cut away, together with some of the adjoining prosencephaUc mass, capsula, lentlcula, and perhaps claustrum, leaving little more than the cortex of the Insula at that point. Defects.— The shading does not discriminate sufficiently between the natural and artlAclal surfaces, but the former are curved while the latter are straight and bounded by sharp lines. The alba and cinerea are not distinguished. The left hemiseptum is added by dotted lines. as along the entire margin of the paraplexus (see Figs. 710 and 737). Corresponding with the margin of the fimbria, the dorsal surface of the thalamus presents a shallow groo ve,the fim- brial sulcus (" sulcus choroideus, " Fig. 707) ; laterad from this the surface is nearly regular, and overlaid partly by the paraplexus and a membrane apparently endyma only, and partly by the thin but more substantial lamina (tenia ?) already described as an extension of the caudatum. The entire dorso-mesal surface of the thalamus, instead of being homogeneous, as it has been sometimes figured and described, may be divided, first and most sharply into a mesal, or entocelian, and a dorsal, or ectocelian, portion, the boundary between the two being the habena and its sulcus. The dorsal surface itself presents a two- fold division into a subfornical (B) and a parafornical (C and D), separated by the flmbrial or choroid sulcus. Finally, the parafornical area is covered partly by the paratela and plexus and partly by the tenia, and may thus be distinguished as subparatelar (C) and subtenial (D), there being occasionally a furrow, the tenial sulcus, between them. The desirability of discriminating be- tween these areas will appear in connection with Pig. 733, where certain different, and perhaps anomalous, con- ditions are described. 175 Brain. Brain. REFERENCE HANDBOOK OF THE MEDICAL SCIENCES. So far as this preparation is concerned, there is abso- lutely no adhesion of endyma to any part of the thalamus dorso-laterad of the habenal sulcus; on the contrary, the endyma is traceable in uninterrupted continuity about callosal f. Fig. 732.— Transection, Partly Schematic, of tlie Fornix and Adjacent Parts at a Level Cor- responding with the Interval between the Medicommissure and the Posteommlssure ; 1,824. X 2.5. 1, Fimhrial sulcus ("sulcus choroideus") ; 2, tenlal sulcus (in some specimens) ; 3, tenial vein ; 4, precerebral arteries ; 5, velar veins ; 6, velar arteries ; 7, habenal sulcus ; 8, Interval (natural ?) between the velum and the commissure of the fornix ; 9, lateral part of the fornix (hemif omix) ; A, mesal, endymal surface of thala^ mus ; B, C, D, zones of its dorsal surface ; B, subfornical ; C, subendymal ; D, subte- nial. Between the left paraplexus and the tenia the membranous floor of the paracele is the paratela. The figure represents the caudal surface of the transection ; the observer is look- ing cepbalad, and his right coincides with the right of the specimen and the figure ; the two sides are substantially identical, but less is shown upon the right ; the meson of the figure, the anatomical middle of the various parts and cavities represented, is dextrad of the middle of the area covered by the figure. Throughout the figure the cavities are shaded and the blank areas represent transected surfaces. The arachnoid is represented by a narrow, straight line, the pia by a corrugated Une, and the endyma by a heavy Une ; the endyma is made to adhere closely to the entocelian surfaces, but the pia and arachnoid are separated sUgMly from the parts which they cover. Preparation. — See Fig. 744, representing another transection of the same brain. The celian parietes were thoroughly hardened before the brain was removed from the skull, and the membranes and plexuses have retained their connections notwithstand- ing much handling and considerable transportation. There is some distortion and dislocation of the loosely connected parts about the fornix, but it has been possible to clear up most of the doubtful points by comparison of the two sides and with adjoin- ing sections. So far as respects the exclusion of the dorsal surface of the thalamus from the paracele, the preparation affords unequivocal evidence. Defects.— As in several other figures representing transections of plexuses, it has been assumed that a plexus consists of a fold of pia covered by endyma ; for present purposes it matters not whether there is a complete fold of the pia, or merely an ex- tension of vascular loops. The ventral lamina of the velum is made too low. 'JTie medicommissure, the dorsal margin of which is included at the ventral side of the fig- ure, did not actually appear in this section, which was just caudad of it, but is intro- duced as a readily recognized landmark. The indnsium is not shown (§ 317) . each paracele, over, in turn, the ventral surface of the callosum, the caudatum, the tenia, the paraplexus, the fimbria, the thicker portion of the fornix, and the hemi- septum, back again to the callosum. § 188. With some specimens the interval between the paraplexus and the caudatum seems to be occupied by a somewhat substantial lamina, separable from the thala- mus, continuous with the caudatum, and perhaps merely a special development of the tenia, but requiring further investigation (Fig. 733). § 189. The point illustrated upon Fig. 733 is the con- tinuity of the paracelian floor from hippocamp to cau- datum without the intrusion of the thalamus. This figure is to be studied in connection with the transection (Kg. 732), and the dorsal view of the floor in Fig. 735. There are, however, differences between these and other preparations which are not easy to explain, except- ing upon the general supposition that a region in which the conditions are nearly peculiar to the human brain might naturally be expected to present individual peculiarities and even anom- alies. § 190. There seems to be considerable variation in the details of the parts in- volved in the apparent representation of the thalamus within the paracele; tliis is perhaps to be expected, since the conditions that have made the usual state- ments possible constitute a great and perhaps peculiar modification of the primitive and typical relations — ^indeed, almost a malformation. It is hoped that the fore- going descriptions and fig- ures may at least serve to induce anatomists to investi- gate the subject in all its bearings. § 191. In What Sense does the T7ialamua Form Part of the Floor of ths Paracele {Lateral Ventricle)? — So widespread and so deeply rooted seems to be the notion that the thalamus con- stitutes a part of the paracelian floor in the same sense as do the caudatum and the hippocamp, that, much as I would prefer to avoid the critical attitude, 1 am induced to comment upon the cur- rent representations of this region. Admitting, for the sake of occupying common ground, that a certain area of the dorsal surface of the human tliala- mus is covered by endyma; that it is continuous with the caudatum, and that therefore, like that body, it enters into the composition of the paracelian floor; none will deny that an adjoining area of this same dorsal surface is as dis- tinctly covered by pia; that it is con- tinuous with the optic lobes (gemina), and like them wholly excluded from the encephalic cavity. To represent the entire dorsal aspect of the thalamus as a smooth, unbroken surface is practically to affirm one of two things : either the whole is pial or ectocelian, which would be in contra- vention of the obvious facts; or else the whole is endymal or entocelian, which would involve not only the gemina but the cerebellum and oblongata, a mani- fest reductio ad absurdum.* § 192. The CoUiculi.— Tins collective term is applied to the rounded emi- nences and ridges which project into the paraceles ("lateral ventricles") from their parietes. They are the caudatum (caput and Cau- da), hippocamp ("hippocampus mc0or"), calcar ("hippo- campus minor "), collateral eminence, and occipital emi- nence. Excepting perhaps the first, each of these * For a fuller discussion of the relations of the thalamus to the para- cele, and for commentaries on the misrepresentations in standard works, see the first edition of the Eefekenoe Handbook, vlii., 144- 147, and Ix., 107, and my papers, 1888, a, and 1889, d. The delicacy of the membranes, the readiness with which they are detached along a ripa, the rough handling to which brains are commonly subjected during the ordinary processes of removal and examination, the slight degree in which preservatives can reach the parts in question when the entire organ is merely immersed as usual, and, finally, the fact that some agents, excellent for microscopic purposes, do not well pre- serve the endymal attachments— all these conditions conspire to bring it about that the endyma across the wide rima should be torn, and the dorsal surface of the thalamus protrude through the rent. 176 REFERENCE HANDBOOK OP THE MEDICAL SCIENCES. Brain. Brain. represents a corrugation of the entire thickness of the parietes, the ental elevation (colliculus) being collocated with an ectal depression (Assure) ; this collocation is in- dicated in the list of total fissures, § 258. § 193. Tlie Gallosal Eminence. — Besides the coUiculi named in § 193, all of which are more or less distinct in at least some adult brains, there is one which is perfectly obvious in some fetuses (Fig. 734, 1), and which, from its apparent collocation with the callosal fissure (Fig. 743), may be called, provisionally, the callosal eminence. It, the hippocamp, and the occipital eminence form an ir- regular triradiation. Its commencement and disappear- ance require further observation, but its unbroken con- tinuity with the hippocamp confirms the idea that the callosal and hippocampal fissures are essentially parts of one, merely deflected by the splenium of the adult. § 194. The relative size of the coUicull is not the same in the adult as in the fetus. This is clear from the com- parison of Fig. 734 with Figs. 744 and 761. The callosal eminence may disappear wholly ; the occipital is seldom recognized (Fig. 744); the collateral is certainly less prominent in the adult than in the fetus (Fig. 734). § 195. Fig. 734. illustrates : A. The contiguity of the margins of the fimbria and the tenia (the edge of the caudatum) with just room for the entrance of the para- plexus, and the concomitant complete exclusion of the thalamus from the paracelian floor (compare Figs. 783 and 733). B. The existence of an ental ridge (1) at this period, continuous and corresponding with the hippocampal and callosal fissures ; whether it extends still farther cepha- lad, as in Fig. 743, cannot be ascertained from this speci- men. C. The branching off of a ridge corresponding ap- parently to the occipital fissure, and representing the adult occipital eminence. flmbrla. D. The existence of two intermediate ridges, perhaps prefiguring the calcar and collateral eminence. I Sylviana paraplexus I caudatum ■ fimbria 1 occipital eminence ,occipilal f. calcar — collateral eminence collateral t. ■-—hippocamp -— .meclioomu FIG. 734.— Left Hemlcerebrum, Laid Open, of a Fetus Weigbing 88 gm. (3 ounces), Measuring 15 cm. from Heel to Bregma, and Esti- mated at Fourteen Weeks ; 2,083. X 1.5. Preparation..— Tbe letus was received fresh ; the bead was cut off and pinned by the neck to a cork loaded with sheet lead ; a shawl pin was inserted as a handle at one side of the head. A sUt was made through the scalp at the lateral angle of the prefontanel, and the guarded cannula adjusted so that ninety-flve-per-cent. alco- hol should enter the paracele gently, with opportunity for egress at the side of the cannula. After six hours the allnjection was discon- tinued, but the specimen remained in alcobol for two days, when the scalp was removed and tbe specimen placed in ten-per-cent. nitric acid. After five hours the calva was so far decalcified that it could be cut away with the scalpel and scissors without jarring the very delicate brain. The left hemlcerebrum was then exposed as indicated, and the nape of the neck removed to expose the collateral fissure. Upon a larger scale some of the points would have ap- peared more clearly. medlcomu. Fig. 733.— Dissection, Partly Schematic, of theFloor of theLeftParacele ("Lateral Ventricle"), Caudal Aspect; 2,345 and 2,347. Xl.5. Com- pare in part with Fig. 706. 4, Lateral sulcus of the mesencephal ; 3, oculomotor nerve ; 5, line of somewhat sudden deflection of the splenlal fibres caudad into the occipital lobe ; 6, large vein ; 7, flmbrial sulcus ; 8, angle between the fimbria and the hippocamp ; 9, hippocampal fissure. Pr-eporafton.— The arteries were Injected with the red glue mixture, and the cavities with alcohol. When hardened, a thick sUce was taken by one transection at about tbe middle of tbe length of the callosum and another at the splenium, just shaving off the tip of the epiphysis. The original transection of the brain stem between the mesencephal and epencephal was modified by carrying two sections cepbalo-mesad, meeting at the level of the valvula. On the right of the cerebrum the parts were left undisturbed, excepting that the paraplexus was raised so as to expose the floor of tbe cavity. On the left, a thin slice of the hemlcerebrum is left attached to its opposite by the pla. In order to expose the paraceUan floor as completely as possible from this point of view, the sections had to be made in many directions. The paraplexus was trimmed down for a certain distance ; then a wedge-shaped piece was cut from the thick caudal wall, hippocamp, etc., including part of the thinner floor, fimbria : this exposed the velum, the double fold of pla between the dorsal surface of the mes- and dlencephal and the ventral surface of the fornix. Very cautiously then the two parallel incisions were carried across tbe floor to and into the caudatum constituting the lateral wall ; the strip so enclosed was then lifted ; it included (1) a piece of tbe fimbria; (2) the disconnected part of the paraplexus ; (3) a strip of the thin lamina Intervening between the plexus and the caudatum ; In 2,347 all these were found separable from the dorsal surface of the thalamus, substantially as in the transection, Fig. 732 ; in 2,345 there were com- plications which should form the subject of monographic consideration. See § 189. Defects.— The defects of the figure are due mainly to the attempt to combine the appearances presented by two different preparations. Vol.. II. — 13 REFERENCE HANDBOOK OF THE MEDICAL SCIENCES. Fig. 735.— The Paraceles C" Lateral Ventricles ") ol an Adult Male, Exposed from the Dorsal Side ; 2,867. X 1.3. Prepa/ratUm.—Tbe entire body (an emaciated consumptive, weigliing only 37.71 kgm., 83.25 pounds) was aUnjected through the fem- oral artery. Eight and one-half Utres were introduced on the first day, and some escaped from the mouth. On the second day, and again on the fourth, another Utre was injected. On the Hfth day there was in.ieoted a litre of Pansch-Gage starch mixture (see article JBroim : Methods, etc.). When the brain was removed, on the eighth day, the only odor was of the alcohol. The substance had already hardened somewhat and the arteries were well filled, notwithstanding some of the mass had extravasated into the thorax. The brain was tran- sected through the mesencephal (see Brwim: Methods), and the paraceles exposed by removing the dorsal portion of the cerebmm in thick sUces down to the level of (he callosum ; then in thinner sUces and wedge-shaped pieces tiH the desired condition was reached. On the left the medicornu was exposed into the part extending cephalad ; the terminal portion extending also mraad could not be shown with- out cutting away an undesirably large mass. On the left also the occipital lobe was cut to a slightly lower level than on the right; hence, on the right appears the dorsal slope of the calcar, while on the left the plane ol section coincides with the line of Its greatest elevation, and the width of the postcomu is correspondingly reduced. To lessen the width of the figure a part of the lateral convexity was removed by dorso-ventral incisions between 3 and i, and 4 and 5, so the line representing the pia ceases at 3 and 5. Finally, the left paraplezug was trimmed oft quite closely. (For the rest of this explanation, see at bottom of page 179.) 178 REFERENCE HANDBOOK OF THE MEDICAL SCIENCES. Brain. Brain. I 196. Fig. 735 illustrates : A. The general relation of the paraceles (lateral ventricles) to the cerebrum; air though relatively much smaller than in the fetus, they are absolutely extensive; here their natural extent has been maintained by the injection of alcohol; when ex- amined in a fresh brain or in one hardened in the usual way their walls are often found nearly in contact.* B. The terminal dilatation and squareness of the post- comu, as contrasted with the pointed form which usually exists in brains not prepared by filling the cavities; sometimes, indeed, there has been doubt as to the extent of the postcomu, as admitted by Huxley, Zool. Soc. Proceedings, 1861, p. 350; in Krause's "Handbuch" (1880), Fig. 479, the postcornua are merely linear. C. The great thickness of most of the parietes as com- pared with their thinness in the fetus. Fig. 667. D. The retention of the fetal tenuity of a portion of the mesal wall, viz., the hemiseptum (halves of the septum lucidum). B. The considerable length and width of the human pseudocele (fifth ventricle) ; so far as I have observed it is wider than in any other animal ; in Fig. 726 (of the sheep) it is unnaturally wide. F. The relation of the cortex (cerebral ectocinerea) to the medulla (alba), as an ectal layer following the fissural indentations. G. The relation of the insula to the Sylvian fissure; the former is a typical siibgyre, the latter is a typical superflssure. H. The relation of the claustrum to the insular cortex €ctad and the lenticula entad (see also Fig. 783). I. The constitution of the caudatum by two regions, a larger cephalic, the caput, and the Cauda, narrow, and following the curve of the medicomu. J. The junction of the occipital and calcarine fissures so as to constitute as it were a single bifurcate fissure. K. The size and distinctness of the collateral eminence, an ental elevation or coUiculus, corresponding to the col- lateral fissure upon the ventro-mesal aspect of the cere- brum. L. The existence, on the left, of an elevation, the oc- cipital eminence, corresponding with the occipital fissure. This colliculus is distinct in the fetus (Figs. 734 and 761), and in some adults (Fig. 744) is better marked than in this specimen. M. The location of the portas (foramina of Monro), and their visibility in a direct dorsal view of the para- celes ; by reference to Figs. 720 and 734, it will be seen that each porta opens into the corresponding paracele obliquely, looking laterad, cephalad, and also dorsad; hence it is visible from three different directions at right angles with one another. N. The distance between the two portas. Deducting the sUght length of the passages themselves, this dis- tance represents the width of the aula^ the mesal division of the prosocele, which is commonly reckoned as merely the cephalic part of the " third ventricle. " O. The continuity of the hemiseptum, a part of the mesal wall of the paracele, with the fimbria, a part of its floor; indeed, their topographical relations may be illus- trated by bending a sheet of paper or metal, and holding *Tlie paper of E. A. Splteka (1900) will contain an account of the topofi^pbic relations ol tlie paraceles to tbe cerebral surfaces. it so that one portion is vertical and the other nearly horizontal; the former will represent the hemiseptum, the latter the fimbria. P. The narrowness of the human fornix as measured by the distance between the lateral margins of the two flmbrias in their horizontal portions : compare the sheep, Fig. 736. It is true the ■word fornix does not occur on the figure ; but, as discussed in § 197, the fornix is constituted by the two hippocamps, with their flmbrias, united at the meson by the commissure (Fig. 732); in this dissection the commissure is invisible, being upon a lower plane, so the fornix, as a whole, cannot be indicated. Q. The smallness of the paraplexus as compared with its fetal condition. Figs. 667 and 747. R. The formation of the free margin of the paraplexus by the medicomual vein, considerable in size and more or less contorted, by which the blood of the plexus is re- turned to the velar vein. S. The considerable width of the attached portion of the paraplexus. This appears on the left side where the plexus has been trimmed quite closely. The rima is the line of apparent interruption of the parietes for the in- trusion of the paraplexus, and is unusually wide in this specimen. T. The completeness of endymal continuity and celian circumscription. These terms have been discussed in §§ 63-66, as exemplified upon the mesal aspect of the brain. Fig. 687. There only the mesal cavities are visible. In the present figure (aside from the pseudocele, which is not a true member of the series) there appear only the great lateral cavities of the prosencephal. The continu- ity of the endyma is represented by the uninterrupted heavy line surrounding either paracele. Likewise is the endyma a continuous sheet upon the sides and floor of this cavity. At the margins of the rima it may be traced as a smooth surface upon the intruded paraplexus, and its cut edges are represented on the left in this figure. I am aware that several authors claim or admit the exist- ence of orifices along the medicomu whereby the neuro- lymph may escape therefrom into the adjacent subarach- noid space; but I am compelled, at present, to regard these as artifacts, like the half-dozen ruptures of the endvma near the porta in the preparation shown in Fig. 721 ."• U. The apparent entrance of the thalamus into the composition of the floor of the paracele. This condition is presented on the left side ; on the right it is hidden by the overlapping paraplexus. § 197. Fornix is a collective noim, a comprehensive name applied to a congeries of parts, each of which has its own name, and all of which, with a single exception, may exist in lower vertebrates and in man or other mam- mals, in certain anomalies, without the formation of the fornix as a whole. § 198. Columns of the Fornix. — In each hemicerebrum there is a bundle of fibres ascending from the albicans and thalamus, passing just caudad of the precommissure, forming the cephalic boundary of the porta, diverging presently from its opposite, pursuing a curved direction along the floor of the medicornu and ending in the tem- poral lobe ; in the aulic region, where it is most compact and exposed, this is commonly called an " anterior pillar of the fornix " ; see Fig. 739. § 199. Hippoeanvp (^^ hippocam/pus ma^or ''''). — In each (Fig. 735.)—!, Cut surface, extending meso-ventro-cephalad ; 3, cut surface of the genu, the cephalic curvature of the eallosum : part of Its nat- ural, pial surface Ues just cephalad ; the transverse lines on the areas 2 and 9 are Introduced merely to indicate the direction of the callosal fibres, not as representations of microscopic structure ; 3, point of disappearance of the pia as a result of cutting away part ol the lateral convexity of the cerebrum ; 4, meeting-place of the two oblique cut surfaces caused by the exposure of the medicomu ; 5, point of reap- pearance of the pia, which was interrupted at 3 : 6, is an area just caudad of the left calcarine Assure ; 7, the occipital fissure ; 8, the occip- ital eminence (see under De/ecfs) ; 9, oblique cut surface of the splenium, of which a part of the natural surface is shown just caudad ; 10, the cut edge ol the paratela covering the thalamus ; from 10 a line should pass mesad to the narrow area between the two lines. De/ects.— The alcohol had so bleached the oinerea as to render the recognition ol Its outlines somewhat dilBcult, so Jhe width ol the cortical zone is only approximately accurate. ,^ , , x^ ^.x, ,. The absence of shading upon the larger part of the surface would imply that it is all upon one level ; really, however, the highest part corresponds nearly with the length of the exposed portion of the right caudatum, and from that level there are gentle slopes cephalad, cau- dad, and laterad. The cut edges ol the hemiseptums are also at a lower level than the adjacent lateral parietes. Not all of the arteries are represented. The occipital eminence (8) is indistinct upon the right and made too small upon the left. The cut edge of the paratela (10) is made too thick and the relations of parts are indistinct (see § 191). On the left, near the word fimbria, is a defective patch of shading du ' to a blemish in the paper. The arachnoid is represented distinct from the pia at only two places, viz., on the right, near the cephalic end, where the former crosses the wide mouth of a fissure, while the latter dips into it as a fold, and at the collosal fissures, just caudad ol the splenium. 179 Brain. Brain, REFEKENCE HANDBOOK OF THE MEDICAL SCIENCES. hemicerebrum there is a corrugation of the entire thick- ness of the parietes, resulting in the formation of a total Assure, the hippocampal (§ 259, C), and an ental eleva- tion, or colliculus, the hippocamp, along the medicornu ; the hippocamp is thickened also, and in- timately associated with the fibres of the column already men- tioned. § 200. Fimbria.— In each hemicerebrum be- tween the hippocamp, with its corresponding cortex, and the rima, or line of intrusion of the paraplexus, there is a zone consisting of alba alone, and form- ing, as it were, a mar- gin for the hippocamp (Figs. 733, 735, and 759). This is the fim- bria {corpus fimbriatum, tmnia hippocampi). § 201. The column and its caudal, curved extension, the hippo- camp and the fimbria, are simply portions of the prosocelian pari- etes, mainly of the par- acelian floor; they are continuous with the mesal wall, hemisep- tum (Fig. 732), and thus indirectly with the roof (callosum) ; excepting at the ven- ,,-- ,, tral end, in the tip of '^iVf'Ll^SS^V' ''"*''^ the temporal lobe, how- Fig. 736.— Tte Left Hippocamp and Ad- joining Parts. X 6. (From Quain, altered from Hirsclifeld and LeTeiU&) 1, Apex of the temporal lc*e ; 1', un- cus ; 2, cut surface of tbe cerebral me- dulla surrounded by the cortex ; 3, at the apex of the postcomu : 3', collat- eral eminence ; 4, part of the spleni- um, nearly medisected ; 4', points to the caloar ; 5, cut end of the lateral portion of the fornix which is contin- ued at the hippocamp (5') and the fimbria (6) ; 6, the fimbria ; 6', the terminal expansion of the hippocamp. ever, their substantial continuity with the caudatum and tenia Preparation. — The left occipito- temporal region of the cerebrum was separated from the rest, together with a part of the splenium and fornix, and , ,, ,. » the dorsal and lateral parietes of the and other portions ot postcomu and medicornu sUced away the paracelian parietes ?e°nTonheravttS"'''^' '"""''" i? interrupted by the De/ecfs.— The specimen had not rima. it would be been allnjected, and the figure looks perfectly legitimate, somewhat diagrammatic, especially as thprpfnrp tn rlpsiirnntp to the dentate gyre (7); the actual ex- ineieiore, to aesignate tremity of the medicornu does not ap- the irregular, elongat- pear (see Fig. 728). There l8 no indi- ed portion of either cation, along the free margin of the „„™ppiian flnnr pnm- fimbria, that one surface of this lamina pardcena,n noor, com was covered by pia and the other by en- posed ot hippocamp, dyma, and that they were continued In fimbria, and fornicol- and upon the removed paraplexus. ^^^^^ j,y ^ special name, e.g., liemifornix. § 202. Commissure of the Fornix. — The parts compos- ing either hemifornix pertain each to its own hemicere- brum, and in brains in which the callosum is undeveloped, these Jiave no connection across the meson dorsad of the aula and portas, representing the primitive mesal cavity of the prosencephal. So far as I know, the fornicommis- sure is thinner in man than in any other mammal; Fig. 731. § 203. The fornix is monographed by Honegger in the Recueil iSawe (zoologie), 1890, v., 311-434. The hippo- camp has been treated by Alex. Hill, in a paper of which an abstract is published in the Royal Society Proceedmgs, vol. iii., p. 5. Variations in the form of the hippocamp and the collateral eminence are described by Howden in Joum. Anat. and Physiol., xxiii., p. 283, January, 1888. J. G. MacCarthy has described an interesting feature of the hippocampal structure in Joum. Anat. and Physiol., xxxiii., p. 76, 1898. In the same journal are several re- cent papers by G. Elliott Smith discussing instructively the fornix and the commissures generally. § 304. Lyra. — When the fornix is transected through the columns (Fig. 737) and turned caudad the exposed ventral surface, including the splenium, is seen to pre- sent lines which have been rather fancifully compared to the strings of a harp ; the lyra is not a part, but merely § 205. Fig. 737 illustrates : A. The general form of the velum, a double fold of pia between the thalami and the superposed cerebrum, one of the layers belonging to each of the two segments (Fig. 710) ; the great veins are between the two, and others enter them from adjoining organs. The free lateral margins of the velum project into the paraceles as the paraplexuses (Fig. 720), and its rounded apex hangs in the aula and the two portas as the auHplexuses and portiplexuses (Figs. 731 and 734). B. The triangular form of the fornix ; the cephalic, or "ascending " part, consisting of the two parallel columns, constituting the so-called "anterior pillar": it expands caudad, the sides being incurved instead of nearly straight, as with the cat, and at the splenium is quite wide. Each lateral half here is practically composed of Fig. 737.— The Velum and Lyra. X 1..5. (From Qualn, after Sappey and Vlcq d'Azyr.) 1. The narrower cephalic part of the velum ; 2, left paraplexus, the margin of the velum which enters the paracele as the paraplexus ; 3, left velar vein, partly covered by the right ; 4, columns, with small veins said to come from th9 callosum and sep- tum, the precornual veins ; 5, tenlal vein ; 6, medicomual vein ; 7, thalamic vein ; 8, vein from left medicornu ; 9, posteornual vein ; 11, body of fornix, transected and reflected ; 12, lyra ; 13, on the lateral part of the fornix ; 14, splenium. (The names here employed for the veins are those adopted in the article Brain, Ci/reulation of. In this volume.) Preparation.— 'With a preparation such as is represented In Fig. 735, If the fornix were transected at its middle (/ ), the caudal half turned caudad, and the cephalic halt, with the attached hemisep- tums, removed down to the middle of the height of the portas, the appearances would be nearly as in the present figure. X>6/6Cf8.— The relation of the parts shown to the rest of the brain would be clearer if there were included at least an outline of one side or of the adjoining region. The tenias are omitted, between which and the f ornical margins, fimbrias, the paraplexuses enter ; at the mesal side of each paraplexus should be a line, a ripa, indi- cating where the endyma covering the plexus was torn or cut in the separation of the fimbria. The whole, especially the lyra, is some- what idealized. the corresponding hippocamp and fimbria, which, as they continue along the medicornu, are sometimes called the " posterior pillar. " 180 REFERENCE HANDBOOK OF THE MEDICAL SCIENCES. Brain. Brain. C. The nature of the lyra (§ 204). The line from 13 ends at the meson, the location of the fomicommissure or thin part connecting the thicker lateral portions. D. The double relation of the splenium to the callosum and the fornix. The larger part, body, of the callosum consists of fibres which pass laterad, dorsad of the para- celes, constituting their roof ; at the splenium some fibres pass dorsad, some caudad, some ventrad, and others in intermediate directions ; now all the constituents of the fornix form parts of the floors rather than the roofs of the paraceles, and at the splenium fornix and callosum become continuous. § 306. ModiflcatioTis of the Prosocelian P(vrietes. — Pri- marily the cerebrum is a pair of lateral extensions of a small mesal rudiment, the first (cephalic or " anterior ") encephalic vesicle ; this forms their only bond of union with one another and with the other segments; their walls are thin and vary little in thickness or composition. Secondarily, the two hemicerebrums are closely conjoined by the callosum and other commissures; between the cerebrum and the crura (and thus the oblongata, the myel, and indirectly the entire body) are developed ex- tensive fibrous communications, the capsulas or " internal capsules " ; the parietes are, for the most part, extraordi- narily thickened, the most notable, and physiologically the most important of these increments constituting what are commonly called the "corpora striata," from the ap- pearance presented on sections of alternating strips of alba and cinerea. Each striatum, however, is now recog- nized as composed of an entocelian ("intraventricular.") portion, the caudatum, and an ectocelian (" extra ventricu- lar ") portion, the lenticula (" lenticular " or " lentiform nucleus "), separated by the capsula already mentioned (Figs. 739 and 783). § 307. Tlie Gaudatum and Lenticula. — With all Rep- tiles, Birds, and Mammals, and at a very early period, the lateral wall and floor of the paracele present a more or less distinct elevation ; in man, and some other mammals, the form is such as to suggest the application of caput to the cephahc (precornual) portion, and cauda to the taper- ing continuation along the medicornu, thus of ccmdatum to the entire mass (Fig. 735). Between the caudatum and the cortex the greatly thickened hemicerebral wall presents (a) the medullary lamina called ea/psula (§ 308) ; (J) next the cortex, a sub- circular disc of cinerea, the claustrum (Figs. 739 and 783) ; and (c) the lenticula, consisting of three zones, all more or less striated, the ental the smallest, and the ectal, also called putamen, the largest. The lenticula, like the claustrum, may be a dismemberment of the cortex. This entire region, from caudatum to operculums, is of great' morphological as well as physiological interest and should be studied in the other mammals. § 308. Ga/pmila and Corona. — As already stated (§ 306) the capsula or " internal capsule " is the thick layer of fibres between the caudatum and thalamus mesad and the lenticula laterad; it is continuous with the crura caudad, and expands in the substance of the cerebral alba in such a way as to be called there corona (radiata). The histolog- ical and physiological aspects of the capsula and corona are considered in other articles; here an attempt will be made to indicate only their topographical relations by explanations of the accompanying figures (738 and 739). § 309. Fig. 738 illustrates: A. The general relations of the alba (medulla) to the ectocinerea (cortex). B. The locations of the two great masses of entocinerea (central tubular gray), the caudatum and the thalamus. C. The intermediate position of the lenticula, as a blunt wedge-shaped mass between the caudatum and thalamus. D. The position of the capsula (" internal capsule ") as a stratum of alba between the lateral lenticula and the other two masses, and constituting a fibrous path for motor and sensory conduction between the cortex and the crura. E. The existence of two zones in the lenticula, the more lateral being distinguished as putamen; a third would have appeared at a level farther ventrad (Fig. 739). F. The existence of a thin, clnereal lamina ectad of the lenticula, between it and the cortex; this is the claus- trum ; it and the cortical corrugations of this region are shown upon a larger scale in Fig. 783. § 310. Mg. 739 illustrates : A. The existence and rela- tive positions of four important masses of connecting fibres, the callosum, columns of the fornix, precommissure, FBONTAL LOBE precornu fomicolumn v"i lenticula thalamus postcomu OCCIPITAL LOBE Fig. 738. — Longiseotion ol tlie Right Hemlcerebrum at the Level of the Aula. X .05. CFrom nature [2,397] and from Gray.) PreparaUon.—The mesal outlines o( the removed ft'ontal and occipital regions were adapted from Gray. The plane ol section corresponds nearly with the direction of the dotted Une from avJa on ng. 739. The line J., B, C should have been dotted. This line and the one parallel with it mesad by the "internal capsule " were introduced with reference to another figure which is not given here. and chiasma, differing from one another in either their direction or their appearance upon this section. The most ventral, the chiastna, is mainly a decussation, as described in the article Cranial Nerixs. The next, pre- commissure, is a true commissure, connecting correspond- ing regions of the temporal (and frontal?) lobes; at the meson it is seen as a raised transverse band, but laterad, on account of its deflection caudad, it is divided ob- liquely, and appears as an elliptical dotted area. The two columns have at this level a nearly dorso-ventral direction, appearing as raised bands just dorsad of the precommissure (the line from the word aula ends upon the right), but they are curved in such a way as to be divided obliquely in two places — one at the level of the precommissure, and the other about 1 cm. (on this scale) dorsad. Finally the callosum, a true commissure, unit, ing corresponding regions of the cerebrum, is divided in the direction of its fibres. B. The general relation of parts and cavities at this important level. Two segments are represented — the diencephal (thalami, chiasma, and diaterma) and prosen- cephal (the remaining and much the larger part). Of the cavities, the mesal space between the chiasma and pre- commissure is the cephalic part of the diacele, the dark- est portion being the optic recess. The prosocele is rep- resented by the aula, the mesal space dorsad of and including the precommissure; by the considerable lateral cavities, pa/raceles; and by the intervening ^oria«. All these are true encephalic cavities, but the dark triangular area still farther dorsad is the pseudocele. ,181 Brain. Brain. REFERENCE HANDBOOK OF THE MEDICAL SCIENCES. Three kinds of surfaces are included, viz. : entocelian, lined by endyma; ectocelian, covered by pia; and pseu- docelian, -with no distinct membrane. There is ecto- cinerea (cortex), entocinerea (caudatum and thalami), and '-•callosal I. callosum pool of paraoele tenia paracele caudatum 3 - fomicolumn (d) aula [ — porta claustrum putamen lenticula Z lentlcula 3 insular cortex opercular cortex precommissure (1) amygdala fomicolumn (v) "■^- precommissure (m) dlacele temporal lobe Fig. 739.— TransecMou at tlie Chiasma and Precommissure, Caudal Aspect. (From Dalton, by permission.) Reduced one-sixth and modified (compare Figs. 724, 738, and 782) . 1, A subgyre (covered gyre) at the bottom of tbe su- percallosal fissure ; 2, margin of the cortex dorsad of the callosal fissure ; 3, tenlal vein ; 4, the cephaUc part of the thalamus, faintly outlined on the other side ; 5, capsula. JDe/ects.— The dots representing out fibrous areas are too heavy. The lines representing the callosal fibres are diagrammatic ; one of them is interrupted. The pseudocele Is not specified. The area of the thalamus is too vaguely indicated. See § 210. what may, for the sake of a general term, be called medi- cinerea, the lenticula, and the claustrum, probably dis- memberments of the ectocinerea. C. The extension of the hemicerebrum nearly equally in three directions from the place of its morphological centre, the porta ; were this brain not somewhat depressed by its own weight, the width and height would be nearly the same. D. The thickness of most of the parietes as compared with the earlier fetal conditions shown in Figs. 667 and 716 ; the hemiseptums and the terma, however, have re- tained their tenuity in great degree. E. The absence of the crista which was seen in a young brain (Fig.. 793), and is constant in the cat (Fig. 686) ; whether it is absorbed or merely obscured in the human adult is not known (§ 366) . F. The overlapping of the proseucephal at the sides of the diencephal, of the cerebrum upon the thalami. G. The relations of the several layers of alba and cinerea between the thalamus and the lateral surface of the cerebrum. The capsula (5) has an oblique direction, dorso-laterad, between the thalamus and caudatum and the lenticula (see Fig. 738). The lenticula itself com- prises three more or less distinct segments, each extend- ing farther dorsad than the one mesad of it ; all present the alternating lines of white and gray which led to the application of striatum to the united lenticula and cau- datum. The thin lamina of cinerea between the putamen, the most lateral division of the lenticula, and the insular cortex is the claustrum, and the alba between it and the lenticula is commonly, but inappropriately, called the " external capsule. " H. The relations of the insula to the parts just named, and to the overlapping gyres which constitute the oper- culums (see Fig. 783). I. The relation of the cinereal mass called amygdala to a Assure opposite pia the m of postoper- intercerebralf. f?f^«™' 7'^^'^'^ ^^ thence been called supercallosall. ^j^^ amygdaline fis- sure; but it is doubtless homolo- gous with the post- rhinal of quadru- peds. (§ 372, Fig. 765.) ■ § 311. Besides the precommissure, a medisection dis- plays two extensive lines of cut surface (Figs. 670, 683, 687, and 765), indicating that there was a continuity of the apposed, mesal sur- faces of the two hemicerebrums. Of these the dorsal, more extensive and more substantial, is the oallosnm (Figs. 734, 737, 739, and 740); the ven- tral is the commis- sure of the fornix (Figs. 733 and 743). § 313. Oallomm. — When the fresh hemicerebrums are divaricated, as in Fig. 740, the bot- tom of the intercer- ebral Assure is seen to be formed by a white mass which unites them for more than the middle third of their length; upon hardened brains this, the callosum {corpus callosum, trabs cerebri, etc.), is easily determined to be fibrous, and somewhat Arm in consistency, and to extend into the hemicerebral masses. At about the middle of its cephalo-caudal extent, the trend of the callosal fibres is almost directly laterad, but at the cephalic and caudal ends, especially the latter, the direction is oblique, giv- ing rise to the conditions known as pi'eforceps and post- forceps (Figs. 735 and 740). The rounded cephalic region of the callosum is the genu, and the caudal, the splenium. As seen in medisections (Figs. 670, 687, and 743) the genu appears like a folding of the callosum upon itself; the ventral continuation being the rostrum, which, in man and other primates, is connected with the terma by the thin copula. The gentle curve of the genu gives to the cephalic part of the pseudocele a rounded outline. § 313. Fig. 71)2 illustrates : A. The primary continuity of the hippocampal and callosal fissures, and of the frontal extension marked 1. B. The existence of several early fissures, some of which are probably transitory. C. The continuity of the callosum, fornix, and terma. D. The degree of separation of the callosum and the fornix at this period, and the concomitant form and ex- tent of the pseudocele. § 314. Splenium. — This region of the callosum is much less easy to understand than the genu from the study of normal adult brains, but most of the difficulties are re- moved or diminished by the study of fetal and hydro- cephalous specimens (Figs 743 and 743). From these it. is clear that, like the genu, the splenium represents a, 182 REFERENCE HANDBOOK OF THE MEDICAL SCIENCES. Brain. Brain. flexion of the callosal sheet upon itself so that there is a dorsal lamina, a ventral lamina, and a caudal connecting portion; commonly the dorsal and ventral portions are callosum Fig. 740.— The Dorsal Aspect of ttie Callosum, Exposed by Divaricating the Hemlcerebnims. (I'rom Quain, after Sappey and Fovllle.) X 0.5. 1, Dorsal surface of the body of the callosum ; 2, mesal ridge or raph^ ; 3, lateral ridges, bounding furrows in which, sometimes at least, are lodged Vas preoerebral arteries ; 4, lateral ridge, said to be formed by the arching of the callosum over the paracele ; 5, cepballc curved margin, genu ; 6, caudal curved margin, splenlum ; 7, preforceps, callosal fibres passing cephalad into the frontal lobes ; 8, post- forceps, fibres entering the occipital lobes; 10, cephalic portion of the cal- losal gyre, the line crossing the cepha/- 11c end of the superoallosal fissure ; 11, callosal fissure ; 12, caudal part of the callosal gyre, the line crossing the para^ central gyre ; 13, cephalic sunace of the cerebellum, the number being just cau- dad of the occipital fissure. Preparation.— WbUe fresh the dor- sal portions of the hemlcerebrums were separated widely; the curved margin of the callosal gyre ("ej/rus fornicor- tus") has been detached and pushed lat- erad so as to expose more completely the extension of the callosal fibres into the hemicerebrum ; caudad this gyre has been divided. See § 212. um are parts of the mesal wall of the precomu and postcornua respectively, while those which compose the ventral lamina and the splenium are parts of the para- splenium fornix ! I , callosum p^ourt-oele t Fig. 742.— Mesal Aspect of the Left Hemicerebrum of a Fetus, Measur- ing 16.8 cm. from Heel to Bregma, and Estimated atjElghteen Weeks ; 2,(h4. X 1.5. 1, GephaUc extension of the primitive callosal fissure ; 2, 3, 4, 5, short but distinct radial fissures, some of them probably transitory ; 6, point of reflection of the endyma from the fornix at the dorsal end of the porta ; 7, point of reflection of the endyma at the Hp of the rima upon its other margin, the tenia, which has been removed ; 8, region which would have become the uncus ; 9, tip of the temporal lobe ; F. hmp., the hlppocampal fissure ; G. dnt., the dentate gyre (fa«ciola or fascia denlata) ; L. ol., olfactory bulb. Preparation.— The fetus was 111 preserved and the head dis- torted; the entire head was medisected with a scalpel; the brain was so tender that the caudatum and plexus broke loose. Defects.— The terma is shown too thick ; the tenderness of the specimen did not permit determining the location and form of the chiasma and precommissure. diaterma chiasma splenlum pseudocele fornix precommissure tuber in close contact, but in hydrence- phals (Fig. 743), as in the fetus at a certain stage, they are separated by a considerable interval; in these cases the pseudocele has a greater extent and a somewhat rounded caudal end. For the most part the callosum extends dorsad of the paraceles, thus con- stituting their actual (though not primary) roof; but the fibres ex- tending obliquely cephalad and caudad from the genu and spleni- * This neuter noun is employed to des- ignate the primitive, undifferentiated mass or rudiment of a part, thus in the sense of Anlage of the German embryologists (as adopted by Minot and others), and of fmidament, as proposed by Mark (" Com- parative Embryology"). It avoids cer- tain obvious objections to those terms as English words, is shorter than prlmardi- Mm (proposed by WUley), and is in har- mony with the following phrases from Aristotle, kindly quoted b^ President B_. I. Wheeler: to irpiaTOv; rt nfmnt vKifs if ^ptoTTj airia. Fig. 741.— Six Diagrams of the Devel- opment of the Human Callosum ; to be viewed from below upward. The chiasma and tuber are introduced merely to facilitate orientation by comparison with Figs. 670 and 687. In A the primitive end wall of the mesal series of cavities Is undiffer- entiated but reinforced by the chi- asma which demarcates the tuber below and the terma above. In B the terma is reinforced by the pre- commissure, and its dorsal end (margin really, but seen as an end in medisectlon) is enlarged, consti- tuting the proton * or rudiment of the callosum and fornix. In C the elongation of the whole terma ren- ders more obvious its demarcation into the diencephalic portion (dia^ terma) and the prosencephalic (pro- soterma) ; the calloso-fomical pro- ton presents a slight cavity or vacuole, the proton of the pseudo- cele. In D the callosum, fornix, and pseudocele are enlarged espe- cially caudad. In E and F the proc- ess continues and all the adult structures are seen. The lateral wall of the pseudocele is the hemi- septum, and it (the pseudocele) is never in communication with either the ental or the ectal surfaces. celian floors, continuous with the fornix (Figs. 733 and 744). § 215. Mg. 743 illmtratea: A. The complete separation of the fornix and callosum as far as the splenium, which is thus a com- mon bond between them, although usually, and perhaps properly, reckoned as a constituent of the callosum only. B. The concomitant extension of the pseudocele and of the hemi- septum. C. The large size of the porta. D. The wasted appearance of the visible gyres, in contrast with those of Chauncey Wright (Fig. 788). § 316. Mg. 744 illustrates: A. The continuity of the splenium with both the floor, roof, and caudo-mesal wall of the paracele ; some of the fibres pass dorsad, some ventrad into the hippocamp, while others, constituting the post- forceps, extend caudad into the calcar, dorso-caudad into the occip- ital eminence, and ventro-caudad into the collateral eminence. B. The unusual distinctness of the occipital eminence, this being, in fact, the preparation in which it first attracted my attention (comp. Fig. 761). C. The prominence of the cal- car, here seen, of course, greatly foreshortened ; of the left hippo- camp only a segment of the caudal convexity appears in this prepara- 183 Braiu. Brain. REFERENCE HANDBOOK OF THE MEDICAL SCIENCES. tion, with the collateral eminence iust beyond (compare Fig. 735). § 317. Indusium. — This term (coupled with the adjec- tive gri^eum) was given by Obersteiner (1893, p. 88) to supercallosal fiesvire porta pseudocele d callosam fornix chiasma Fig. 743.— Mesal Aspect of Part of the BlgM Hemlcerebrum of an Adult Hydroceplialus ; 747. X .7. The dorso-ventral line, d i\ Indicates the transection plane represented in Fig. 731. 1, Splenium ; 2, ven- tral surface of fornix ; 3, subsplenial gyres ; 4, 5, ? ; 6, collateral As- sure ; 7, uncus ; 8, hippocampal Assure. The tip of the temporal lobe, included by the interrupted line just cephalad of v, indicates what was removed to expose the parts shown in Fig. 728. the thin layer of cinerea upon the dorsal surface of the callosum. It has been discussed by Giacomini, Blumenau, and more recently by Fish, 1893, as.* § 318. In several (perhaps half a dozen) brains in the Cornell museum the callosum presents a de- cided thinning at about the junction of the middle with the splenial third; most if not all of the individuals were mentally defect- ive in some degree. § 319. IncaUosal Brains. — In addition to about fifteen cases of shortness or thinness of the callosum, there have now been reported at least a dozen instances of its complete ab- sence, together with the mesal part of the fornix. Commonly this deficiency was ac- companied with mental and physical weak- ness, amounting often to idiocy ; but Malin- verni reported {Oiornale del R. Acad. Torino, 1874 ; Gazette medicale de Pa/ris, January 16th, 1875; Gazetta delle Gliniche, 1874, No. 15; London Medical Record, 1874, No. 73) the case of a soldier, forty years of age, who had been noted merely for melancholy, taciturnity, and lack of neatness. A case of total absence of the callosum and fornix is described and figured with unusual fulness by Alex. Bruce, in Brain, xiii., 171-190. There are included abstracts of previous cases and reduced copies of the illustrations of some. § 320. Fig. 745 illustrates : A. The absence of the callosum and of the commissure (mesal part of fornix). B. The development of the columns as far dorsad as a point corresponding apparently to the dorsal limit of the aula and porta (which is not distinctly indicated). C. The roofing in of the aula and diacele by a thin (membranous?) tela, the remnant of the primitive roof of the cavities. D. The absence of the medicommlssure and small size of the precommissure, in contrast with the same parts in the incallosal cat (§231). E. The independence of the occipital fis- sure, and the a/ppa/rent junction of the calcarine with the hippocampal. F. The radial disposition of the mesal fissures ; some of them probably represent the transitory fissures men- tioned in § 337. § 331. Among other mammals than man the total ab- sence of the callosum has been observed, so far as known to me, only in three cats examined in the anatomical laboratory of Cornell University ; one of these (No. 881) has been described in my paper (1883, c), and was repre- sented in the first edition of the Refeeenob Handbook, Fig. 4,835. At the Boston meeting of the Association of American Anatomists, December 39th, 1890, 1 showed the brain of a sheep (No. 3,844) in which the callosum is rep- resented, if at all, by a short thin lamina ; but this speci- men, fortunately unmutilated and thoroughly hardened, has not yet been figured or described. § 323. Pseudocele ( ffth ventricle," " mntriculus septi pellucidi"). — This compressed, subtriangular mesal cav- ity has no connection with the true encephalic cavities either in the adult or at any stage of development. Its anatomical relations are shown in Figs. 687, 733, 735, and others; but they are more clearly understood from the series of diagrams in Pig. 741 based upon my own speci- mens and the account of Marchand ("Ueber die Ent- wickelung des Balkens im menschlichen Gehirn, " Archin fur mikr. Anat., xxxvii., pp. 398-334). § 333. In the cat (Fig. 683) and mammals generally, both the anatomical and developmental conditions are different. The fornix commissure and the callosum con- stitute portions of two lines of secondary junction of the two hemicerebrums and are continuous at the splenium ( snpercallo- ' i sal fissure . . .callosal f. callosum ( occipital ' ( eminence , calcar collateral eminence .hippocamp * I have to record with some chagrin that, upon a series of transections of an adult brain (1,824), sections of which are shown in Figs. 732 and 744, hardened in a mixture of ammonium dicbromate and alcohol, the con- tinuity of the cinerea upon the callosum was recognized in October, 1880 ; notwithstanding its significance, fur- ther examination and publication were deferred. Fis. 744.— Transection of an Adult Brain through the Splenium ; 1,824. X 1. 1, Postcomu ; 2, section of a subsplenial gyre. Prep(waUon. — The brain was that of a Pole, male, and was received in the head through the kindness of Dr. F. Gary, a former student. With the special object of furnishing reliable preparations for the elucidation of the celian pari- etes (see Fig. 732), the sides of the head were sawn off so as to expose the medi- comu, and tnto this was injected a mixture of alcohol (95°) and water, each 2 litres, ammonium dicbromate, 10 gm.; the same was injected into the arteries. When the brain was completely hardened it was removed and transected at in- tervals of about 1 cm. Defect.— The lines representing the callosal fibres should be continued across the meson. 184 REFERENCE HANDBOOK OF THE MEDICAL SCIENCES. Bralu, Brain, as in man ; but cephalad the callosum ends as a point so tliat the triangular area is not completely circumscribed ; commonly, also, the interval corresponding to the pseu- docele is narrower than in man. § 324. In three apes (orang, gorilla, and chimpanzee*) gations of the wall (Pig. 747). They do not branch. Their general direction is radial. By the end of the fourth month they disappear from the lateral surface (Pig. 748) and partly at least from the mesal, although there is reason to believe that two of them may be prac- R. gyn. fomlc lam. term. abn. ™'°' '^°''''- sulc. call. marg. !. ! r r praeouD. flss. par. occ. cun. sulc. occ. trans, flss. clc. / -ling. col. ant torn. sp. luc. / .- com. ant. 1 1. perf. ant. tr. opt. ■g. Wpp. sulc. occ. temp. ml. schn pulv. thai. gyr. unc. Fig. 745.— Mesal Aspect ol the Eight Hemlcerehrum of an Incallosal, Microcephalic, Adult Brain. X .93. (From Onulrowicz.) Ahn., abnor- mal radiating Assures ; Cpl. ant. forn., fornicolumu ; Gam. ant., precommissure ; Cun., cuneus ; Fiss. clc, calcarine Assure ; Wiss. par. occ., occipital Assure ; G. hipp., hippocampal gyre ; O. unc, uncus ; L. perf. ant., precrlbrum ; Lam. term., terma [aulatela and dia- telaj ; liner., subcoUateral gyre ; proecun., precuneus ; Pulv. Thai., pulvinar (of the thalamus) ; B. gyr. fornic, margin of the callosal fyre (gyrus fnmicatus) ; Schn., out surface between the diencepbal (thalami, etc.) and mesencephal (gemlna) ; Sp. luc, hemiseptum [?] ; ulc. call, marg., supercallosal Assure [?] ; Sulc centr., central Assure ; SmJc. occ. temp, inf., collateral Assure ; Sulc. occ tr., " trans- verse occipital Assure " [?] ; Tr. op , optic tract. Prepcwotion.— This was the brain of a male idiot, thirty-seven years of age, who had never learned even to feed himself ; It seems to have been o]titaiued fresh early and well preserved ; the paper C Daa balkenlose Mikrooepbalengehirn Hotman," ArcMv filr Psychiafrie, 1887, xvul., pp. 1-24) from which the figure is taken is by Onufrowioz, but this and most of the other figures are by Porel. There are sev- eral transections, but the lack of distinct Indication of endymal continuity renders them less instructive than they might have been. The weight of the entire brain is not stated. See § 320. and in all the monkeys examined by me the conditions are as in man ; the mode of development is not known to me. § 335. To English-speaking anatomists interested in the morphology of the cerebral Assures and com- missures are particularly commended the recent writings of T>. J. Cun- ningham, and G. Elliot Smith in the Journal of Anatomy and Physioloijy. § 326. Fig. 746 illus- trates: A. The condition and relative size of the encephalic segments at this period. B. The presence of transitory Assures which are absent from the other hemicerebrum (Fig. 673). C. The indication, so far as these transitory fis- sures are concerned, that in this individual the right hemicerebrum was more advanced than the left. § 227. Transitory Fis- sures. — During the third and fourth months both the lateral and mesal sur- faces of the cerebrum present linear depressions corre- sponding with ental ridges and thus representing corru- * A gibbon brain has not yet been available. Fig. 746.— Eight Side of the Brain of a Fetus Measuring 49 mm. from Nates to Bregma, and Esti- mated at Twelve Weeks; 1,828. X 1.4. (The left side of the same is shown in Fig. 673, where the mode of preparation is described.) tically perpetuated by the formation of the permanent ealcarine and occipital fissures along the same lines (Fie. 730). § 228. Fig. 747 illustrates : A. The great size of the paraceles and paraplexuses at this stage; compare Pig. 667. a lateral fissure paraplexus a mesal colliculus a lateral colliculus a lateral gyrus a mesal Assure 1 part of falx Fig. 747.— Transitory Fissures of a Fetus Measuring .'5-6 cm. from Ver- tex to Nates, and Estimated at Fourteen Weeks ; 2,770. X 2.2. Prepcwattoji.— After the exposure of the brain the frontal end of the cerebrum was sliced ofl: so as just to clear the large paraplexuses. Of the falx all was removed excepting the fragment shown. The head was tilted so that the face is much foreshortened. 185 Brain. Brain. REFERENCE HANDBOOK OF THE MEDICAL SCIENCES. B. The slight and nearly uniform thickness of the parietes. C. Suggestion of a wrinkling or corrugation of the parietes as if from growth within a confined space. transitory Assure quadrigeminum Sylvian lossa Sylvian fossa Fig. 748.— Fetus Measuring 7 cm. from Nates to Vertex, and Estimated at Fourteen Weeks ; 3,761. X .9. Neg. 1,090. Beceived in weak alcohol and injected through the umbilical vein with alcohol and 2inc chlonde. D. The approximately symmetrical distribution of these corrugations. E. The length of the Assure on either side, reaching from the Sylvian fossa nearly to the meson. F. The absence of any indication of branching. § 329. Mg. 748 illustrates: A. The large number of transitory fissures at this stage. B. Their general arrangement as radiating from the Sylvian fossa; compare, however, Fig. 747. C. The considerable difference in their length ; one of the longest is indicated by the line from "transitory fissure"; one of the shortest is just below it. § 330. Trandtory Fissures Prob- ably Mechanical in their Origin. — The simplest explanation seems to be that their formation is due to the growth of tlie cerebral walls at a rate more rapid than that of the cranium; and that their dis- appearance results from the yield- ing or more rapid growth of the cranium. § 331. Fig. 749 illustrates: A. The disappearance of the trans- itory fissures, at least upon the lateral aspect. B. The concomitant increase in the length of the cerebrum, apparent- ly from the development of the occipital region; compare Figs. 667 and 673. C. The non - appear- ance of the lambdoidal fissure (Fig. 750) . D. T h e commence- ment of the postoper- culum as a fold of the temporal lobe projecting over the Sylvian fossa. . , , E. The non-appearance at this stage of the other oper- culums or of any elevation indicating the future insula. § 383. Abnornial Persistence of Transitory Msswres.— In several brains lacking the callosum {e.g., the one shown in Pig. 745), the mesal permanent fissures present the radial arrangement characterizing the transitory fissures. This condition likewise exists upon the lateral aspect in the case described by Hans Virchow and shown by Cunningham (1893, Fig. 7). § 333. Are Tranntory Fissures Peculiar' to the Hvman Pmm.?— Hitherto, as remarked by Cunningham, they f iii-„ X'^ _ ^jST - - Fig. 749.— Fetus Measuring 8.8 cm. Irom Vertex to Nates, and Esti- mated at Pour Months ; 2,644. X .9. It is not very well preserved and the cerehrum is evidently shrunken. FIG. 750.— Dorso-Caudal Kegion ol the Cerebrum of a Fetus Meaaurmg about 30 cm. from Heel to Bregma, and Estimated at Six Months; 1,817. X 1. 1, Sagittal suture; 3, lambdoidal suture; 3, nght lambdoidal Assure ; 4, left lambdoidal Assure. Preparation.— The entire fetus had been preserved in alcohol. From the left side the calva and dura were removed, excepting a narrow strip along the meson ; on the right there was left a trape- zoidal area, 12 to 25 mm. wide, including most of the sagittal and lambdoidal sutures. have been observed only in man. Before, however, con- cluding that they constitute a real human peculiarity they should be looked for in the other primates, where I believe they will be found at corresponding periods of development; the examination of the fetal gorilla de- scribed by Duckworth will be interesting in this respect. Cunningham has considered the transitory fissures quite fully, but the subject re- quires further investiga- tion. §334. Lambdoidal Fis- sure. — In several fetuses estimated at from three to seven months I have observed a fissure direct- ly underlying the lamb- doidal suture (see Figs. 750 and 761, and my pa- per 1886, a). It is ap- parently identical with what are called by Cun- ningham "external cal- carine ", and " external perpendicular" (1893, a. Plates I. and II.); but I am unable to concur in his disposition of the matter or to decide whether the fissure dis- appears or persists (see Fig. 777). § 385. Fig. 750 illus- trates : A. The distinct collocation of a fissure and suture at this period. B. The early appear- ance (or late disappear- ance?) of this, the lambdoidal fissure; ex- cepting, perhaps, the dorsal end of the occipi- tal, the rest of this re- gion is smooth. 186 REFERENCE HANDBOOK OF THE MEDICAL SCIENCES. Brain. Brain. C. The peculiar sharpness of outline, reminding one of the transitory Assures (Figs. 746 and 747 ; § 327). § 236. Intereerebral Fissure. — The interval between the apposed, mesal surfaces of the two hemicerebrums is the intefrcerebral fissru/re ("interhemi^pheral," preaylvian I. operculum. Sylvian I. 1 I insula | central t. olfactory bulb Fig. 751.— Left Fetal Hemicerebrum ; 1,820. X 1. 1, Orbital region, unflssured ; % temporal lobe, unflssured ; 3, sllgbt furrow, the pre- occipital fovea; 4, circular depression, unldentiUed (see % 241). Prepcwattora.— The fresh hemicerebrum was placed in a mixture of alcohol and glycerin, equal parts ; after two days half the mix- ture was replaced by alcohol ; after two days more alcohol alone was used, and renewed on the following day. The original mix- ture seemed to prevent the usual distortion of fetal brains, and to facilitate the removal of the pla. Unfortunately the age and size of the fetus were not recorded. or "great longitudinal") (Fi^s. 682, 707, and 739). It differs from ordinary fissures in the following respects: 1, It is mesal or azygous, while all others are lateral or in pairs ; 2, although its sides are formed by cinerea, its bottom, the callosum, is apparently alba, with a com- paratively thin layer of cinerea, the indusium, § 217 ; 3, although the pia has the usual relation, the arachnoid, instead of passing directly across, dips into it to a greater or less depth on account of the f alx (Figs. 687 and 733) ; 4, it is, in one sense, a superflssure (§ 328) since in its depths are concealed the callosal fissures. § 237. Poles and Lobes of the Cerebrum. — The two ends of either hemicerebrum are distinguished as the frontal and occipital poles respectively, and the tip of the temporal lobe as the temporal pole. For topographical convenience, and not be- cause they represent perfectly natural di- visions, either anatomical, histological, or physiological, each hemicerebrum may be regarded as forming five lobes, the insula and the frontal, parietal, occipital and tem- poral lobes (Figs. 757 and 758) . In a gen- eral way, but by no means accurately, the last four lobes coincide with the cranial bones for which they are named. § 238. The insula (Johus operfus, "cen- tral lobe ") is nearly or quite covered in the adult brain by folds (operculums) from the adjoining lobes (Figs. 763 and 767); except- ing at part of the ventral side the insula is surrounded by an irregular furrow, the circuminsular fissure (Figs. 781 and 783). § 339. The other four lobes have more or less complete natural boundaries on either the lateral or mesal surface, but not on both. The primary division is by the line of the central fissure (Fig. 751) into a frontal region and an occipito-temporo-parietal re- gion. The former, although commonly ac- cepted as a single lobe, is so extensive as to be conveniently subdivided by a line continued dorso- cephalad from the presylvian fissure into a postfrontal and prefrontal lobe, the latter including the orbital sur- faces § 340. The region caudo-ventrad of the central fissure line is divided first by the occipital fissure into a — ""'"' and an occipito-temporal portion, and the latter again into a temporal and an occipital lobe by artificial lines drawn from the preoccipital fovea, the indentation of the ventral margin corresponding with the petrous portion of the temporal bone (represented by the emargination opposite the word collateral in Fig. 757) to the splenium on the mesal aspect and on the lateral to the extremity of the Sylvian fissure. § 341. Mg. 751 illustrates: A. The early appearance of the Sylvian, presylvian, and central fisures, and of a depression which perhaps represents the beginning of the paroccipital. See the ventral surface of this specimen (Fig. 789). B. The nearly uncovered and slightly fissured condi- tion of the insula at this period ; the faint dorso- ventral line just caudad of the end of the line from insula rep- resents the just commencing transinsular fissure. § 343. Permanent Mssures. — The surface of the adult cerebrum presents alternating depressions, fissures, and elevations, gyres (or " convolutions "). The fissures vary in depth from 1 mm. to 30, and in length from 1 cm. to 10. The intervals between the fissures (and thus the width of the gyres) vary greatly, but an adult brain seldom presents an unflssured surface more than 30 mm. in width. Notwithstanding considerable variations in different brains, and in different parts of the same brain, one can hardly fail to be impressed with the approximate uniformity of the interfissural spaces (when viewed squarely, as suggested under Fig. 763), as if the fissures were produced mechanically by the extension of the sur- face within a confined space. § 348. Mg. 752 illustrates: A. The condition of the insula and operculums at this stage. The former is dis- tinctly elevated, but as yet perfectly smooth, while in the otherwise less advanced brain shown in Fig. 751 it has a slight transinsular furrow. The subsylvian fissure is just forming as the ventral boundary of the preoper- culum. B. The demarcation of the subfrontal gyre by the sub- frontal fissure. C. The non-continuity of the parietal and paroccipital fissures. D. The non-appearance of the precentral and post- central fissures. E. The peculiar triangular depression which seems Bupercentral f __ .»_ snperfrontal f subfrontal (...- 4- prenylvian f . — 6absylvlaxtf...i oUactoi; bnlb. - parietal f. .^ Sylvian f . -.6 .-...paroccipital f. .. .Bupeitemporalf.. _... .postoblongata FIO. 752.— Lateral Aspect of the Left Half of the Brain of a Fetus, Size and Age Un- knovm ; 2,278. X 1. 1-8, Fissures not Identifled with certainty. On the temporal lobe, just dorsad of the pons, the apparent Assure is an artmcial crack. Preporatfoji.— The brain was medlsected while fresh and this halt placed in al- cohol upon its mesal aspect ; it has become thinner and wider than natural, but ex- hibits the Assures more perfectly on this account. to represent the commencement of the supertemporal flsstire. F. The presence of three fissures or series of fissures caudad of the supertemporal, the middle of which may represent the exoccipital (§ 344). G. The interruption of the central fissure near its dorsal 187 Brain, Bratn. REFERENCE HANDBOOK OF THE MEDICAL SCIENCES. end ; so much as appears in the figure is continuous, but near the mesal margin of the hcmicerebrum is a slight depression separated from the longer lateral portion by an isthmus (comp. Fig. 773). H. The small size of the cerebellum, the distinctness of the flocculus, and the prominence of the oliva. callosum fornix .paracentral t. i — . . .calloBal f. supercallosal f . pseudocele olfactory t olfactory bulb... Tig. 753.— Mesal Aspect of tlie Left (Reversed) Hemicerebrum of a Fetus, Size and Age Unknown ; 2,278. X 1. The lateral aspect of the left half of the same brain Is shown In Fig. 752. 1, 2, Rostral fissures ; 3, tip of temporal lobe ; 4, ventral end of hippocampal Assure ; 5, uncus ; 6 (should have been extended a Uttle farther so as to reach the light band), fimbria ; 7, dentate gyre {fascia dentata) ; 8, un- determined fissure. central f . paracentral g. ._ : \ paracentral f . _ ^a callosal g. \^^ callosal f _. callosum § 244. A cerebral fissure is a narrow space vacant of brain tissue and containing only a fold of piawith blood- vessels ; yet it has many and sometimes important rela- tions, a complete account of which would embrace about fifty distinct topics. There are also about one hundred problems of a more or less general nature applying to several or all of the fissures. § 245. Mg. 75S illuitrates : A. The existence of three in- dependent furrows between the callosum and the margin of the hemicerebrum along the line of what is common- ly called the calloso-marginal fissure. B. The distinctness at this period of the four total or collicular fissures, occipital, calcarine, collateral, and hip- pocampal. C. The independence of the occipital and calcarine. D. The extension of the calcarine alone nearly or quite" as far as the point reached in some other brains by the occipital alone or by the stem of the two. Sometimes the occipital is the longer in the fetus and occasionally, as in Fig. 754, union fails to occur. § 246. Mg. 7S4. ilhistrates : A. The complete separation of the calcarine fissure from the occipital by a calcarine isthmus. On the other side the two are connected as usual. B. The bifurcation of the calcarine at each end, consti- tuting a long zygal fissure (§ 307). C. The extension of the occipital fissure so as to represent what is usually the common stem of it and the calcarine. D. The presence of a "spur" extending caudad from the occipital toward the calcarine upon the isthmus. E. The appearance of trifurcation of the dorsal end of the occipital. The middle extension, however, is con- splenlum - 6 ■ fasciola occipital 1. - hippocampal g. _ collateral f . _ subcollateral g. — 7 — tinuous with the fissure only superficially ; the cephalic branch is apparently my adoceipital ; the caudal, although doubtless the dorsal part of the occipital, presents an unusual curve and is invisible from the lateral aspect. F. The extent of the precuneal fissure. G. The considerable extension of the central upon the mesal aspect. H. The presence of a subcalcarine fissure. § 247. Each of the forty or more fissures demands monographic treatment; but the limits of this article will permit the detailed consideration of only two, the central (§§ 269-303) and the paroccipital (§§ 309-825), as exemplifying different phases of fissural study. § 248. Fig. 75S illustrates: A. An early stage in the formation of the Sylvian fissure, the presylvian fissure being represented by a mere notch. B. The incomplete separation of the calcar and the occipital eminence. C. The size of the postcornu relatively to that of the entire hemicerebrum. D. The corrugation constituting the collo- cated calcar and calcarine fissure. E. The equally distinct collocation of the occipital fissure at this period with the ad- joining colliculus, occipital eminence, some- times called " bulb of the posterior cornu. " Collocation of Permanent Fissures with Cranial Suiwi-es. — In the adult the dorsal end of the occipital fissure has a notably constant position at the mesal angle of the lambdoidal suture, as seen in Pig. 670. With fetuses of between three and seven months this suture is decidedly caudad of the occipital fissure, but is distinctly -precuneal!. 'A«-4jS^l;«iS.^[fc. precuneus ™»a TjaK»j«. _ adoceipital f. iL^ ^B t^WWIt. 1 [ occipital f . cuneus. calcarine isthmus 2 calcarine f . subcalcarine g. subcalcarine f . postcalcarine f . collateral f. § 249. FIG. 754.- Caudal Half of the Mesal Surface of the Right Hemicerebrum of an Adult Female Paretic. No. 2,358 In the Museum of Cornell University. X 1. collocated with the lambdoidal fissure (Pig. 750); this collocation does not persist after the seventh month, and it is not yet known whether the fissure disappears or changes its position. The approximate collocations of the central and other fissures with sutures are considered in the article Brain, Surgery of the. 188 REFERENCE HANDBOOK OF THE MEDICAL SCIENCES. Brain. Brain. § 250. Fissures should T)e studied before gyres, because: 1, They are simpler, being represented by lines instead of planes : 2, they are more commonly entirely independ- ent of other fissures; 3, they are comparable with the rivers of a region which are employed as boundaries of ,- Sylvian 1, ,. occipital em. ^occipital 1. ' postcomu calcar collateral em. "■"--lilppocamp ~~-~paraplexu3 collateral f. Fig. 755.— Left Hemicerebrum of a Fetus, Size and Age Unknown. Opened from the lateral aspect ; 1,819. XI. 1, Obliquely cut surface; the unshaded area repre- sents a surface cut parallel with the meson. The line from paraplexus ends somewhat vaguely ; it should reach the narrow zone between the blppocamp and the cut surface marked 1. See 8 248. paracele - operculum . presylvian f . - insula. orbital f.._' olfactory bulb. callosum \ callosal f the subdivisions ; 4, themselves structureless, they really represent the locations of a greater amount of cinerea than lines of equal width and extent on the gyres, and have thus a greater, presumptive, physiological sig- nificance, although there seems to be a diilerence of opin- ion as to the functions of the intrafissural cinerea. § 251. With children bom at term the main fissures are always well defined, and in some cases there seems to be lit- tle difference between infant and adult cerebrums in respect to fissural complexity, although the insula is always less devel- oped and less completely cov- ered by the operculums (see Fig. 663). Such brains are often more readil}' obtained and removed than those of adults, and if well preserved and carefully handled may materially aid both teach- ing and research. § 252. For the elucidation of the intricacies of adult fissures, fetal brains are much more ser- viceable than those of monkeys. This, in contravention of the view and practice of Meynert, has been insisted upon by me (1886, g). Some of the pecu- liarities and complexities of the monkey brain are represented in Fig. 787. § 253. Adult cerebrums com- monly present individual pecu- liarities which prevent their serv- ing as types or standards. I have found such in every brain examined; not merely, for ex- ample, ■ in that of the philoso- pher, Chauncey Wright (Figs. 768, 770, 788) but also in that of a mulatto ; simple in several re- spects, it has peculiarities and complexities not as yet fully understood (see Figs. 762-766). § 254. Fig. 756 illustrates : A. In connection with Figs. 668 and 702, the perfection and beauty of form of the human brain at birth. B. The relatively small size of the cerebellum at birth. C. The distinctness and prom- inence of the pons. D. The lateral extent of the pseudocele ; at the genu (cephalic curvature) of the callosum it is 1 mm. deep, representing about one-half of its entire lateral extent. B. The distinctness and depth of the principal fissures and the large number of minor ones. F. The peculiar ventral curve of the cau- dal half of the calcarine fissure, and the con- comitant expansion of the cuneus. G. The length of the fissure in the sub- calcarine gyre. H. The appearance of the cephalic stipe of the paroccipital fissure (18) upon the meson (see Figs. 774 and 775). § 255. The study of fissures upon actual brains is facilitated by reference to diagrams such as have been published by C. L. Dana, Eberstaller, Eeker, Jensen, Pansch, Schafer (in "Quain"), and others. My present views are embodied in Figs. 757 and 758. § 356. Comments upon the Fissural Dia- grams (Figs. 757 and 758). — A. They repre- sent my views at this time, but are not identical with those previously published (1886, g, and first edition of the Refbrencb Handbook), and are subject to furtlier modi- fications with increasing knowledge of the facts. For example, the small fissures caudad of the occipital are but little understood, and the orbito-frontal of Giacomini may prove to be more nearly constant than now supposed. B. An attempt has been made to indicate the relative depth and constancy of the fissures by lines of three de- grees of width ; this grouping, however, is provisional. fornix pseudocele paracentral g. ^central f , paracentral f _i2^ calcarine f. 30 21 olfactory bulb 31 optic u 25 ^ thalamus Fig. 756.— Mesa! Aspect of the Eight Hemicerebrum of a Male Child, at Term ; 478. X .84. Other aspects of the same specimen are shown in Figs. 633, 774, and 775. 1, Postoblongata ; 2, preob- longata ; 3, postgeminum ; 4, pregemlnum : .5, thalamus. Its mesal surface, forming the lateral wall of the diacele : the dorsal, pial surface is designated by the line from the word thalamus : these are parts of one and the same organ, separated by the membranous diatela ; but the trian- gular area dorso-cephalad of them marked pseudocele and apparently separated only by the nar- row white area marked fornix, is the hemiseptum, part of the mesal surface of the cerebrum ; 6, 9,16,17,21,23,24,25,26,31, unidentified Assures: 7, postrhinal; 8, olfactory; 10,11, rostral Assures : 12, supercallosal Assure, continuous with the paracentral ; 15, intraparacentral As- sure ; 14, inAected Assure ; 18, cephalic stipe ofparoccipital Assure ; 19, a ventral branch of the occipital Assure ; 20, 21, intracuneal Assures ; 22, dorsal branch of the calcarine Assure ; with the more caudal of the two ventral branches perbaps it represents the forked Assure sometimes called pontcalcarine ; 27, precuneus ; 28, precuneal Assure ; 29, dorsal end of the occipital Assure ; 30, the common stem of the diverging occipital and calcarine. Defects.— The specimen spread while hardening under its own weight, and is therefore wider and thinner than natural ; tbis is, however, an advantage for the study of the Assures. The naturally considerable cranial Aexure became still more marked as the brain rested upon the lateral aspect while photographing, and this, for convenience, is preserved in the draw- ing. The thalamus is unnaturally, though very instructively, uncovered by the callosum so that Its caudal prominence, the pulvinar, is visible. The habena is not distinctly seen. The cerebellum is not represented accurately as to details, but is enlarged in Fig. 702. The hypophy- sis is lacking, and the aulic region is not shown in detail. 189 Bratu. Bralu. REFERENCE HANDBOOK OP THE MEDICAL SCIENCES. C. Each separate line represents what I now regard as a flssural integer so far as the human brain is concerned. The following are also regarded as integers, although continuous with others: occipital, calcarine, postcalca- infiecied/. Fig. 757.— Diagram of the Fissures upon the Mesal Aspect. The outline and certain Assures are from the mulatto brain (322), which was hardened within the cranium. 1, Postrhinal (amygdallne) Assure ; 2 and 3, rostral Assures. rine, postrhinal. The presylvian, subsylvian, and basi- sylvian are really branches or continuations of the Syl- vian, but are separately named for convenience. D. The fissure lines are nearly straight and simple. nections are (1) of the Sj^lvian with the basisylvian, presylvian, and subsylvian, all which might be re- garded as its continuations or branches ; (3) of the cal- losal with the hippocampal. Gr. Usual connections are of the occipital with the calcarine, and of the supercallosal with the paracen- tral, but there are occasional excep- tions. H. Common connections are of the superf rental and supercentral ; the precentral and subfrontal; the pre- central and supercentral; the post- central and subcentral and parietal ; the parietal and paroccipital. I. Occasional connections are of the precentral with the Sylvian, and of the central with the Sylvian over the margin of the operculum; in these cases, so far as known to me, the junction is seldom very deep. § 357. From the deservedly pop- ular flssural diagrams of Ecker, the publication of which has so materi- ally advanced the general knowl- edge of the subject, these differ mainly in the following respects : A. The omission of branches and contortions. B. The inclusion of the callosal, inflected, adoccipital, postrhinal, postcalcarine, medifrontal, precu- neal, and postcentral fissures. C. The disjunction of the supercallosal from the para- central ; of the precentral from the subfrontal and super- central; of the postcentral from the subcentral; and of the subcentral from the parietal. D. The recognition of the adoc- cipital fissure and the cuneolus. E. The introduction of the ex- occipital as probably representing the true " ape-flssure " of Wernicke. F. The combination of the " trans- verse occipital " of Ecker with the caudal portion of his " interparietal" as a distinct fissural integer, the paroccipital. G. The adoption from various olfactory f, basisylvian / Fig. 758.— Diagram of the Fissures upon the Lateral Aspect. The outline and certain Assures are from the mulatto brain (332), which was hardened within the cranium. M, the "mar- ginal "gyre; A, the "angular" gyre; Preop., the preoperculum ; Subop., the subopercu- lum ; Subsy. f ., the subsylvian Assure. The interrogation points on the lateral aspect of the occipital lobe indicate my doubts as to the existence of certain Assures, or as to the names that should be applied to them il they do exist. The subtemporal Assure Is not shown (see Fig. 765). ^^^^^, postcomu K^jk\ calear A SSK 2J] calcarine f. J^K' Endyma operculum /^^^H ^^.precomu °^^l |[|_jm|. caudatum w^S PySl.insula "^-^ Sylvian I. excepting where branching is a practically constant feature, as, e.g., with the paroccipital, paracentral, pre- cuneal, and postcalcarine. E. The connections are of two distinct kinds: primary, invariable, and inevitable from the mode of formation of the parts ; secondary, and more or less common, but not necessary. F. Invariable and apparently inevitable fissural con- 190 writers of what seem to be the best flssural names of a single word each — e.g., from Huxley, collat- eral ; from Owen, callosal, hi/ppoeam/pal, medifrontal, subfron- hlppocamp hippocampal 1. Fig. 759.— Schematic Transections of the Three Parafiellan Oomua in the Order of their Complexity. See § 259. REFERENCE HANDBOOK OF THE MEDICAL SCIENCES. Brain, Brain. tal, gupereallosal ; tTomWernicke, fronto-margiiial; from Jensen, intermedial; from Pansch, occipital smdpcmetal; from Schwalbe, precentral and postcentral ; from Mey- nert, preoccipital ; from'Lussana and Lemoigne, inflected (Ital.j .inflesso). H. The substitution of several mononyms for polyo- nyms, viz.-: of presyMan for aseendiiig Irranch of the ^kiian ; subsyhian for anterior branch ; ioMsylman for the t)art ventrad of the presylvian ; and the restriction of Sylvian to the "posterior branch." I. The replacement of lingual lobule and fusiform lobule occipital eminence- caloarlne Assure- -^ oalear- postcomu. ]■ - Fig. 760.— Transection of the Left Occipital Lobe of a Fetus, Size and Age trnknown ; 2,278. X 1.5. This figure is almost diagrammatic in Its simplicity ; it shows very clearly the relation of the caloarlne fissure to the caloar as represented in Fig. 759, A. (not at all easy to apply correctly), by subealca/rine gyre and wbcoUateralgyre, names at once associated with the As- sures which respectively constitute the dorsal boundaries. J. The use of one and the same word, fissure, for all the cerebral depressions excepting the two foveas. If. The use of one and the same word, gyre, for all subdivisions of the lobes, excepting the cuneus and pre- paraplexus hlppocamp occipital eminence occipital Assure ealcar \ calcarine Assure _ caudatum paraplexus postcomu lambdoldal f . precentral f subtrontal f superfrontal f Fig. 761.— The Caudal Part of the Bight Hemloerebrum of a Fetus, Measuring 14 cm. from Nates to Bregma, and Estimated at Four Months ; 1,816. X 1.5. (See § 261.) Preparation.- This is part of the specimen shown in Fig. 727, where the mode of preparation is desciibed ; the postcomu was ex- posed by removing the paracelian roof along the lines in that figure. The plexus was partly cut away, although not so represented in this figure. cuneus, already well distinguished by mononyms, and the cuneolus. § 258. Total and Partial Fissures. — Of the permanent fissures most affect merely the cortex and the adjacent alba and are therefore sometimes called pa/i-Ual Assures; the central, for example, though constant and deep, is only a partial fissure. But others represent cormgations of the entire parietes, so that the ectal depression, fis- sure, is opposite and obviously correlated with, an ental elevation or coUiculus; the fissures commonly enumer- central f postcentral t supertemporal f subtemporal f medltemporal I. Fig 762 —Lateral Aspect of the Left Hemicerehrum of a Mulatto ; 322. X .8. 1, Cephahc part of the operculum demareatfid frora the rest by a fissure that does not extend through Its entire thickness ; 2, preoperculum ; 3, postoperculum ; the subs.ylvian fissure is probably repre- sented bv a short indentation, visible only when the postoperculum (3) is removed ; 4, what is commonly called the supramarginal ffvTP " • 5 may represent part of what is called the " angular gyre " ; 6, a supergyre overlapping the concealed, caudal part of the angu- gyre , -, lar ; 7, unidentified occipital gyre may 8 9 Dortions of the unidentiAed supergyre that overlaps the lateral part of the paroccipital gyre ; 10, .'. '. s- ... j.«._»_., „_/■„• tv.» „ 1 1 «„„ 11 "iposlte the dorsal end of the occlp- ' curves ventrad at 6, not real, connections wlti Sie ocdpital and supertemporal fissures) ; 12, curved fissure in the same supergyre, superficiaUy connected with the supertemporal ; 13. cenhallc sttpe of the paroccipital fissure ; U, dorsal fork of the postcentral fissure ; the subcentral is not indicated by a sepM^te num- ber and is continuous with the postcentral; 15, caudal extremity of the calcarine fissure, reaUy simple and independent ; 16, cephahc rSlSs of the triradlate supercentral fissure (see tig. 765) ; 18, 19, 20, umdentified occipito-temporal Assures ; 21, Just ventrad of the strait between the central and supercentral Assures (see Fig. 764) ; 22, the most cephaUc of three distinct fissures crossmg the medifrontal gyre. 191 Brain, Brain. REFERENCE HANDBOOK OF THE MEDICAL SCIENCES. ated as total are the hippocampal (Fig. 755), calcarine (Pig. 760), and collateral (Fig. 755) ; the Sylvian may Fig. 763.— Diagram Illustrating the Effect of the Convexity of the Cerebral Surfaces upon the Apparent Width of the Gyres. TJpon a cylinder were drawn parallel lines at the uniform distance of 1 cm.; one side of the cyUnder was then photographed, and the fig- ure is a reproduction of the photograph, reduced one-half. The reduction of the intervals according to the distance of the lines from the part nearest the eye illustrates the fact, not always dis- tinctly recognized, that the fissures near the periphery of a, cerebral convexity always appear to be nearer together than they really are ; the intervening gyres consequently appear of less than their actual width; see, for example, the superirontal gyre in tigs. 763 and 764. ' possibly be correlated with the caudatum (Fig. 716) ; the callosal and occipital are total fissures in the fetus (Figs. superfrontal f . precentral f. (?) supercentral f . inflected f . central!. j precuneal t. Fig. 764.— Dorso-Cephalic Aspect of the Left Hemlcerebrum of a Mu- latto ; 322. X .8. 1. Caudal radius of the triradlate supercentral fissure; 3, strait between the central and supercentral fissures; 3, caudal end of paracentral fissure (see Fig. 766) ; 4, cephalic end . of the same (?); 5, Sylvian fissure ; 6, postcentral Assure. See 8 264. 734 and 761), and the ental correlative of the latter is sometimes recognizable in the adult (Fig. 744). § 259. Mg. 759 illustrates : A. The mesal wall of the postcornu presents a ridge, the calcar, and the mesal sur- face of the occipital lobe a furrow, the calcarine Assure ; as seen in Figs. 760 and 761, the ectal depression and the ental elevation are obviously correlated. B. The precornu presents an ental elevation, the cau- datum, and a depression nearly opposite, the Sylvian fissure. But the correlation of the two Is not quite clear and the conditions are complicated by the formation of the intrafissural (or intergyral) elevation called insula. C. Here, as In the postcornu, there is no doubt respect- ing the correlation of the ental elevation or colliculus, the orbital 1 olfactory ( olfactory tract optic nerve . calcarine f. Fig. 765.— Ventral Aspect of the Left Hemlcerebrum of an Adult Male Mulatto ; 332. X .8. 1, Bldge ventrad of the splenium, represent- ing, perhaps, one of the gyres described by A. Retzius, British As- sociation Proceedings, 1885 ; 3, stem of the occipital and calcarine fissures. See § 365. Preparation.— See Fig. 757. The olfactory bulb has been re- moved. hippocamp, and the ectal furrow, the hippocampal fissure; in addition, the proper nervous parietes are abrogated along a line, the rima, and the paraplexus is formed by the Intrusion of the pial process covered by the endyma ; the margins of the rima are specialized and become the fimbria and tenia ; on the figure the tenia is not indicated as separate from the caudatum (Fig. 730). § 360. Classification of the Permanent Fissures. — The following grouping of the fissures is approximately nat- ural and has been found convenient by me ; at the best, however, any such arrangements are provisional: * * Whatever may be desirable in theory, or eventually practicable, at present nothing seems to be gained by attempting to classify cerebral depressions as fissures and sulci, and In this article all are designated 192 REFERENCE HANDBOOK OF THE IVIEDICAL SCIENCES. Bralu, Brain. A. Total fissures, representing a corrugation of the entire paracelian parietes; e.g.. calcarine. B. Partial Assures -with some structural correlative; e.g., olfactory. C. Partial fissures, nearly or quite constant, and de- marcating recognized gyres ; e.g., subfrontal. D. Inconstant, intragyral fissures; e.g., medifrontal. § 261. Mg.761, in addition to A and B, specified under Fig. 737, illustrates : A. The contiguity of the two margins of the rima, excepting for the intruded para- plexus. B. The concomitant, absolute exclusion of the thalamus from the paracelian floor. C. The depth and peculiar form of the lambdoidal fissure (Fig. 750). § 263. Fig. 76$ illustrates : A. The form of this adult, mulatto, left hemicerebrum, uoaltered save from alco- holic shrinkage. B. The general aspect of the gyres, comparable with the appearance in the cerebrum of the philosopher, Chauncey "Wright (Fig. 788). C. A simple, almost typical condition of certain fissures, e.g.. central and Sylvian, in a large part of their course, combined with great and unusual peculiarities of the same or other fissures. D. The visibility of the insula (see Pigs. 767 and 788). E. The presence of a vertical branch of the presylvian fissure, which, however, does not extend through the thickness of the operculum. F. The union of the subfrontal with the precentral and with two of the fissures crossing the medifrontal gyre. Q. The apparent narrowness of the superfrontal gyre, which nevertheless, as seen from the dorsal aspect, is of considerable width ; in fact the narrowest portion of the superfrontal is just as wide as is the subfrontal measured in line with the stem of the presylvian fissure ; this is a forcible exemplification of what is explained under Figs. 763 and 764. H. The great length of the supertemporal fissure, and its apparent dorsal branching in four directions ; its true and deep continuation is cephalad between 5 and 10. I. The continuation of the calcarine fissure around the margin of the hemicerebrum so as to appear upon the caudo-lateral aspect as an undivided end (15) ; the calcar- ine is believed to be continuous commonly with a bifur- cated postcalcarine, and the condition in this brain seems to be unusual; see also Fig. 785. J. The superficial connection of the central and pre- ppiitrSil fissures K. The partial appearance of the subtemporal fissure on the lateral aspect ; see, however. Fig. 765. L. The forking of the Sylvian into an episylvian fissure, near 4, and a hyposylvian near 5. § 363. The apparent width of gyres upon convex sur- faces of the cerebrum is affected by the point of view. Compare, e.g., the superfrontal gyre of the mulatto as shown in Figs. 763 and 764. The conditions are schemat- ically illustrated in Fig. 768. . § 364. Mg. 764. ilhistrates: A. The length and mde pendence of the superfrontal fissure, and its close paral- lelism with the hemicerebral margin. B. The width of the supercentral gyre when viewed directly as compared with the oblique view shown in Fig. 763 (see § 263, G). ^ . , C. The triradiate form of the supercentral and its rela- tion to the inflected. D. The continuity of the supercentral with the pre- central and central; in each case, however, there is a vadum or shallow. § 265. Fig. 765 illustrates : A. The presence of a dis- tinct though rounded orbital prominence between the frontal and the lateral portions of the outlines, but the absence of any such boundary between the lateral out- line and the occipital. B. The narrowness of the olfactory gyre, between the olfactory fissure and the mesal margin of the frontal lobe, C. The distinctly zygal form of the orbital fissure. Vol. II.— 13 D. The length and distinctness of the subtemporal fissure. E. The extension of the calcarine fissure upon the oc- cipital end of the hemicerebrum. P. The presence of a fissure (orbito-f rental?) on the orbital surface cephalad of the orbital fissure. § 266. List op Paetial Fissures, Constant or Nearly So, and Demarcating Gyres. Aspect. 1. Basisylvian. . . . Ventral 2. Central Lateral 3. Circuminsular . Lateral 4. Inflected Lateral 5. Insular: Lateral 6. Olfactory Ventral 7. Orbital Ventral 8, Orbito-frontal. Lateral 9. Paracentral Mesal 10. Parietal Lateral 11. Paroccipital . . . Lateral 13. Postcentral Lateral 13. Postrhinal Mesal 14. Precentral Lateral 15. Presylvian .... Lateral 16. Subcentral .... Lateral 17. Subfrontal .... Lateral 18. Subsylvian. . . . Lateral 19. Supercallosal . . Mesal 30 Supercentral. . . Lateral 31 Superfrontal. . . Lateral 23 Supertemporal. Lateral 23 Transinsular. . . Lateral Gyres separated by tbem. Orbital. Temporal. Precentral. Postcentral. Insular. Adjoining. Superfrontal. Precentral. Insular. Orbital. G. rectus. Subfrontal. Orbital. Superfrontal. Orbital. Paracentral. Precuneus, etc. Parietal. Subparietal. Paroccipital. Subparietal. Postcentral. Parietal. Uncus Temporal Precentral. Medifrontal. Operculum. Preoperculum. Postcentral. Parietal. Subfrontal. Medifrontal. Preoperculum. Suboperculum. Oallosal. Fronto-marginal. Precentral.. Super- and medifrontal. Medifrontal. Superfrontal. Supertemporal. Meditemporal. Preinsula. Postinsula. § 267. — List of Inconstant Fissures, with the Gyres in Which They Occur. Fissures. Gyres. 1. Adoccipital Precuneus. 3. Episylvian .^ Subparietal. 3. Exoccipital Occipital (?). 4. Fronto-marginal Fronto-marginal. 5. Hyposylvian Supertemporal. 6. Intermedial Subparietal. 7. Intraparacentral Paracentral. 8. Medifrontal Medifrontal. 9. Postcalcarine Occipital (?). 10. Postcuneal Occipital (?). 11, Postoccipital fovea Occipital (?). 13. Postparoccipital Paroccipital. 18. Precuneal Precimeus. 193 Brain. Brain, eSh. REFERENCE \HANDBOOK OP THE MEDICAL SCIENCES. 14. Preoccipital fovea Subtemporal. 15. Preparoccipital Paroccipltal. 16. Rostral Callosal. 17. Suboccipital Occipital (?). 18. Subtemporal Medl- and subtemporal. 19. Transtemporal Meditemporal. paracentral f . (?) inflected f. ^ '__/ /central t. fronto-marglnal f..,^^*!*" """l^^vT^*"^^.^ occipital t. supercalloaal f . ^^^\^ . ' ^kiP*''*^^^^^ A callosal I..,V^ JD4^— "^ \^ 1 CALLOSAf. O. r A- pBECUNKtlS "■' subcalcanne_g.J olfactory ir '^^^^^^P^'^ ^ ' postrMnal f . y^ve^^u^^^^ i 1 V calearine f. 2 / ; hippo- I collateral I. bippocampal f . campal g. subcollateral g. Fig. 766.— Mesal Aspect of the Left KReversed So as to Appear the Right) Hemicerebrum of an Adult Male Mulatto ; 322. X .5. 1, The common stem of the occipital and calearine ; 2, uncus ; 3, optic tract, divided obliquely ; 4, fornix ; 5, retreating ventral surface of the fornix ; 6, paracentral Assure. There can be no doubt that 6 is the caudal or main portion of the paracentral, but the cephalic portion so named is thought by E. A. Spltzka to represent the intraparacen- tral, the true cephalic limb being absent. Mr. Spitzka concludes (1900) that the inflected, like the central, typically indents the mar- gin of the paracentral gyre. Unfortunately, at this time, I cannot determine the point by re-examination of the specimen; but the need of doing so exemplifies the remark in g 253. Preparation.— 9,ee Fig. 757. Defects.— Most of the flssure lines are too faint ; the emarginatlon of the ventral outline just cephalad of the optic nerve is too decided. § 368. Mg. 766 illustrates : A. The existence and un- usual extent of the fronto-marglnal fissure. B. The complexity of the precuneal fissure. C. The length of the collateral flssure. inflect«d f supercentral f _ precentral f superfrontal f subfrontalf ' — Taking all things into account, the central fissure de- mands first and fullest consideration ; there is, indeed, no fact concerning it that is not worth recording or that may not prove significant morphologically or practically valuable. The order in which the following topics are presented is far from perfect, but it may serve to indicate the many-sidedness of these cerebral features. To save space the pronoun it will commonly designate the cen- tral fissure.* § 370. T?ie Name. — It has been called, to use the Latin forms, fissura, adssura, and sulcus, with the qualifying adjectives centralis, Solandica, and postero-parietalis, all these having, of course, appropriate equivalents in the various modern languages. My doubts as to the utillt3' of discriminating, at present, between fissures and sulci have been expressed In § 360, note. My reasons for pre- ferring central to Bolandic have been stated upon several occasions since 1883 ; but as the former name has now been adopted by the Association of American Anatomists and the Anatomische Gesellschaft it will probably super- ■ sede the latter with anatomists of other nations. § 371. General Location and Direction. — On the dorso- lateral aspect of the cerebrum, at about the middle of its length ; from a point at or near the dorsl-mesal margin, it extends latero-cephalad at an angle of about 70 degrees with the meson, or about 140 degrees with its opposite. § 373. Dimensions. — Among adult hemlcerebrums in , the museum of Cornell University the length of the fissure, measured in a straight line between the two ends, varies from 8 to 10.5 cm., the usual length being about ; 9.5 cm., or about one-fourth of the entire circumference of a cerebrum as measured in a dorso-ventral plane Inter- secting the flssure at about the middle of its length. If measured along the sinuosities, as if the flssure were straightened out, the length may be one-seventh greater than if measured across the curves. The greatest depth varies from 10 to 15 mm. § 373. Relation to Ental Elevations. — There is no evi- dence of any special collocation between It and any ental elevation, in man or any other mammal ; hence, though so deep, it is not a total but a partial flssure (§ 358, A). § 374. Go7istancy. — The only case of absence of the [ central fissure known to me Is that described by Sir Wil- liam Turner {Jour. Anat. and Physiol., xx v., 337-348). presylvian f Sylvian f >^ —^ postcentral f. parietal f. subcentral f. ,__-15 „ J^- supertemporal f . IaSi^ paroccipltal t. A ■ u rl3 , -^13 W-11 ^-10 ^ 9 8 ■7 "->-.^ >« — -^ no. 767.— Lateral Aspect of the Left Hemicerebrum of an Adult Swedish Carpenter, Presenting an Unusual Degree of Fissuration ; 318. X .6—. Preparation.— The hemicerebrum was hardened resting upon the mesal surface, and apparently with Uttle change in form. The right was likewise numerously Assured. Of the unidentifled Assures the only ones that seem to call for comment here are 9 and 10, which are transtemporal Assures, and 16, a well-marked hyposylvlan. See § 275. D. The distinctness of the postrhinal fissure. E. An apparent peculiaritjr of the paracentral fissure as stated briefly in the description; the subject is dis- cussed by B. A. Spitzka, 1900. § 369. Pre-Eminent Importance of the Central Msmre. — The subject was an epileptic, twenty-six years old, and the entire (alcoholic) brain weighed 1, 107 gm. (39J ounces) ; * The central Assure is quite fully discussed by Cunningham (1892, chap. ili.). 194 REFERENCE HANDBOOK OF THE MEDICAL SCIENCES. Brain. Brain. the left hemicerebrum 530 gm. , the right 437. The left fissures are stated to have had a normal development and arrangement, but on the right the Sylvian fissure was termediate caudal convexity. In most adults it is cer- tainly more or less serpentine or tortuous, and the regular curves are sometimes distinct; but three cephalic con- superfrontal t, precentral f. r supercentral f. central f .— u postcentral f. parietal f. pacocclpltail t occipital f subti / central f.— V Sylvian f supertemporal t JFiG. 768.— The Left Hemicerebrum of a Philosopher (Chauncey Wright), from the Dorso-Lateral Aspect. X .9. Preparation. — See Fig. 788. The figure is based upon a photograph taken as nearly as possible at an angle of 45° with the meson, so as to present the dorso-lateral aspect. The line connecting the superfrontal and medltrontal Assures was made inadvertently. The numerals 1 to 22 are at the same points as in Pig. 788 ; on that figure 23 designated the central Isthmus, which here has the word printed upon it : 33 Is just at the end of the short inflected fissure. wide open so as to expose the insula largely ; flie central fissure was wholly absent, together with the precentral and postcentral; the lateral surface presented three arched fissures, demarcating four arched gyres about the Sylvian fissure, a condition analogous to that in the dog and many other carnivora. The interest and importance at- taching to this case would have warranted a larger num- ber of better figures, and a representation of the left hemicerebrum. , § 275. Fig. 767 illustrates: A. The unusual number of minor fissures, especially of the slight depressions which I have called fossnlm. B. The three cephalic curves of the central fissure, and their decided character. C. The extent of the supertemporal fissure. D. The continuity of the postcentral, parietal, and paroccipital fissures. E. The length of the dorsal branch of the presylvian. F. The two dorsal branches of the Sylvian, and the distinct hyposylvian branch (16). G. The crossing of the temporal lobe ventrad of the supertemporal fissure by two transtemporal fissures. H. The non-union of the subfrontal with the precen- tral; this last is not named but is the ventral continuation of the supercentral, beginning about opposite the sub- frontal. I. The continuity of the postcentral, subcentral, pa- rietal, and paroccipital, constituting what has been called the " intraparietal complex " ; § 306. § 276. Topographical Importamee. — This is well indi- cated in the following vigorous declarations of Wagner andEcker: "Mam, muss sie immer ziterst avfsuchen, um Mch wn da in, dem scheinba/ren Chaos der Hirnwirhdungen. ..." " Bildet sie die den sicJiersten Ausgangspunkt fur die Aufmehu'ng der Windungen. ..." § 377. Form, or Course in Detail. — ^According to Broca it normally presents two cephalic convexities with an in- vexities have been observed in sufficient number to show the need of careful observation and tabulation. § 278. Brandies. — OSshoots from the central are usu- ally rather short and straight, starting at the summits of the curves ; but in the brain presenting the most decided^ curvatures (Fig. 767) there is scarcely any branching. § 279. Mg. 768 illustrates : A. The unfamiliar appear- ance of a hemicerebrum when viewed from this oblique aspect. B. The distinctness of the angles between the cephalic and the dorsal and ventral outlines ; this was commented upon by the first describer of this brain, Prof. Thomas Dwight, and appears in Fig. 788, though less markedly. C. The completeness and width of the isthmus between the dorsal and ventral portions of the central fissure ; in Fig. 788 this is marked 23, but is so much foreshortened as to be hardly visible. D. The simple, curved form of the dorsal part of the central Assure, with no bifurcation such as exists at both ends of the ventral portion. E. The independence of the supercentral fissure. F. The presence of a medifrontal fissure subdividing the large area between the subfrontal and superfrontal fissures. G. The junction of the subcentral fissure with the parietal, and the continuity of the parietal with the par- occipital; whether this junction occurs at 1 or at 2 can- not be determined at present. H. The great length of the supertemporal fissure and the complexity of its dorsal end. I. The presence of a long and curved fissure, 6-7, on the lateral aspect of the occipital lobe. J. The presence of an unusual crescentic fissure (14) ventrad of the subcentral (15). § 280. Junctions. — So far as I am aware, connections between the central and other fissures (excepting the in- tercerebral, § 286) are mre, and incomplete or shallow 195 Brain. Brain. REFERENCE HANDBOOK OF THE MEDICAL SCIENCES. when tliey occur; e.g., in Pig. 763, where the concealed vadum between the central branch and the supercentral nearly reaches the surface, and in Fig. 767, where there is also a nearly invisible vadum just at the apparent union of the supercentral with the central. The occasional confluence of the cen- tral with the Sylvian over the margin of the operculum is commonly shallow, but sometimes quite deep, as in the right hemicerebrum of James Burk, figured by Mills {Journal of Nervous and Mental Disease, vol. xiii., Septem- ber, 1886). The depth of such straits should always be stated. § 281. Bifurcation. — Terminal divis- ion of the central fissure at either end is rare; among the few cases known to me the ventral end is bifurcated on the right in a supposed insane person (385) and the ventral on the left of Chauncey Wright (Fig. 768); the dor- sal end is bifurcated on both sides in Professor Oliver (Fig. 664). § 383. Eolation to the Mesal Aspect. — Cunningham found (1893, 163) that the fissure indented the dorsal margin so as to appear on the mesal aspect (as in Pig. 757) in sixty per cent, of the hemi- spheres examined. My own observa- tions would make the proportion some- what larger. For the final determi- nation of the ratio there should be employed only adult specimens retain- ing their natural form. §383. Special Location. — About mid- way between a line coinciding with the precentral and supercentral fissures cephalad, and a line coinciding with the postcentral and subcentral caudad. § 384. How to Distinguish from Ad- joining Fissures.* — When the precentral is separate from the supercentral, and the postcentral from the subcen- tral, the central is notably longer than either. When these two pairs of fissures unite, however, it is the mid- tion. The following characters should be noted in case of doubt: its greater depth and length;; its location relatively to the entire length of the perebrum, and the angle it forms with the margin ; its more complete superlrontal supercentral precentral central (d.) central (v.) postcentral paracentral parietal isthmus p&roc. parocclpital occipital Fig. 769.— Right and Left Paracentral Regions of an Adult ; 3,132. X .5. Each piece was cut from the dorso-mesal region of the hemicerebrum by an incision at about 45° with the meson ; the pieces rest upon the obUque cut surfaces and the dorso- mesal margins correspond approximately to hnes between the two Ds and the two Ms. 1, Dorsal outcrop of the cephalic end of the paracentral, y^hich is also continu- ous with the supercallosal ; 2, a crescentic Assure which. In the foreshortened posi- tion of the parts, appears to join the paracentral, but is really separated from it by a vadum barely below the surface ; 3, a similar fissure on the right, separated by a complete isthmus from the paracentral, which latter has no dorsal outcrop, but is continuous with the supercallosal ; in the light of E. A. Spitzka's observations 2 and 3 may be the inflected fissures. Fig. 770.— Dorsum of the Cerebrum of Chauncey Wright, a Philosophic Writer, Critic, and' Mathematiolan (see description of Fig. 788). X .8., When photographed the cerebrum was inadvertently tilted a little to the left. I, Central isthmus on either side ; tbe num- bers correspond to those on Figs. 768, 779, and 788. independence; the usual absence of terminal forks ; par- ticularly its extension to or across the dorsal margin just cephalad of the paracentral, thus indenting the paracentral gyre (Fig. 769). § 885. Alleged Duplication. — Calori and Griacomini have each described (1884) a brain which they interpreted as having two central Assures nearly parallel and separated by an " intercentral " gyre. The conditions in an educated suicide (3139) were similarly interpreted by me (1894, a) ; but a later comparison with a larger num- ber of brains leads me to conclude rather (1900, a) that the supposed second or cau- dal central is really an unusually long resultant of the union of the postcentral and subcentral, caudad of which is the parietal. The bifurcated dorsal end of the postcentral has the usual relation with the paracentral as it crosses the meson (see Fig. 769).* § 386. Fig. 769 illustrates : A. The more usual relation of the central fissure to the dorsal margin, crossing it so as to appear on the mesal aspect. B. The constant relation of the central supercentral precentral central postcentral paracentral die of the group of three fissures at about the middle of the hemicerebrum having a general dorso-ventral direc- * The macroscopic methods here enumerated might require confir- mation from the histology of the region in question, as indicated in the discussion of my paper, 1900, a, by Donaldson, Spiller, and Mayer (Jour. Nerv. and Mental Disease, October, 1900, 540). * After the above paragraph was in type the kindness of Dr. D. S. Lamb enabled, jQe to ob- tain a transcript of the "Nota preventiva" of C. Leggiardi-Laura (Archiv dl Psich. 'Sci. Penol. ed Antrop. Crlmin., Torino, 1899, pi 4313, "Du- plicita della scissura di Rolando, net jorijninall." It is there claimed that among thirty-seven female brains cen- tral reduplication occurred once, on the left, and among thirty males, twice on the left, once on the right, and once on both side^> In the absence of figures, especially photographs, and detailed- d^crlptions, I must refer these to the same category as my own ; see..also the- remark of Dr. 0. K. Mills upon my paper (1900, a) In J (zygon) ....caudal ramus Fig. 774.— Dorso-Caudal Aspect of the Bight Hemicerebrum of a Child at Birth ; 478. X 1. This figure was published in the Journal of Nervous and Mental Disease, June, 1886. Other aspects of the same brain are shown in Figs. 663, 756, and 775. some species or individuals, and deepest at or about the middle of its length, corresponding nearly with the place of its first appearance. Any marked and frequent shal- lowing of a supposed fissural integer is reason for ques- tioning its integrality, and for seeking, in other individu- als and in allied species, evidence that it really consists of two. § 306. The"intrapanetal* flssure" of Turner -prohaMy represents two flssural integers, the parietal and the paroc- cipital, because (1) in nearly half the cases examined by me there are two flssures separated by an isthmus of greater or less width ; (3) when the two are continuous there is often a vadum at the point corresponding to the isthmus ; (3) each of the two portions, whether separate or continuous, is usually deepest at or near its middle ; (4) at their first appearance in the fetus they are always completely independent. § 307. The typical paroccipital flssure consists ot (a) the zygon or bar, the first part to be formed ; (6) cephalic and caudal stipes continuing the curve of the zygon about the dorsal outcrop of the occipital ; (c) cephalic and caudal rami, imparting to each end the characteristic form seen in Fig. 774. The paroccipital is a typical zygal flssure. § 308. Fig. 775 illustrates, in addition to points seen equally well in Figs. 756, 668, and 775), the greater depth of the paroccipital zygon at the middle of its length, a fact hardly compatible with the supposition that it is only a caudal extension of the parietal, or that the caudal stipe and ramus constitute an independent flssure, the " transverse occipital " of Ecker. § 309. What Is the So- Called "Transverse Occipital Fissure " .' — Most writers seem disposed to adopt the view ♦ Often, but incorrectly, written interparietal. 198 REFERENCE HANDBOOK OF THE MEDICAL SCIENCES. Bralu. Brain. of Ecker that the caudal stipe and ramus of the pai'oc- cipltal represent a " sulcus occipitalis transversus " -which unites with the longitudinal bar or zygon. None of the parocclpital g. occipital t. parocclpital t. / 5 6 \ supe Fi0. 775.— Dorso-Caudo-Lateral Aspect of the Bight Hemicerebrum of a Child at Birth, Partly Dissected ; 478. X 1. See the lateral and dor- sal aspects (Figs. 663 and 774) . 1, Lateral surface of the zygal part of the parocclpital gyre ; this is, of course, pial, but the point of the V-shaped incision reaches a slightly lower level than the bottom of the fissure, occasioning the triangular cut area at the bottom ; 2, Une representing the junction of the zygon with its caudal stipe ; 3, ectal line of the caudal ramus ; 4, ental Une of the same ; 5, should hare crossed the out surface to the outcrop of the Assure marked 7 in Fig. 663 ; 6, the exoocipital Assure (?) ; 7, unidentlBed Assure ; 8, presyl- Tian Assure ; 9, postcentral Assure ; 10, gyre between the postcentral and the parietal fissures ; 11, cephalic slope of the cut surface ; 13, cephalic ramus. PreporatfoTC.— By reference to the lateral aspect. Fig. 663, the parocclpital Assure will be seen to be indicated by the name itself, connected with the middle of the zygon. For the present figure a wedge-shaped removed by two Incisions, starting respectively at the tip of the rami and meet- ing at an obtuse angle at the exoccipital. The re- moval of this piece ex- posed the lateral aspect of the parocclpital gyre and of the gyres adjoining it cephalad and caudad ; also the depth of the zygon and the two rami. specimens examined by me seems to confirm this interpretation, and I am compelled to re- gard the very interest- ing condition shown by Cunningham (1893, Fig. 51) as simply an- omalous. Much, how- ever, remains to be done in this region. § 310. mg. 776 il- lustrates : A. The de- gree of flssuration at this period. B. The early condi- tion of the parocclpital fissure as a upsiloid (U-shaped), depressed line with lateral branches, rami. C. The independence of the parocclpital fis- sures at this period. D. The absence of anj' fissure closely re- . sembling the " trans- verse occipital." E. The distinctness of the inflected fissures at this period. F. The dlfliculties of identifying fetal fissures in the condition of those upon the frontal and parietal regions of this specimen. § 311. Mff. 777 illustrates: A. An almost schematic condition of the paroccipital fissure, simple in form and central f . postcentral f . paracentral f. 3 parietal f. parocclpital f . occipital f . lambdoidal i. (?) Fig. 777.— Dorao-Caudal Aspect of the Occipital Region of the Right Hemicerebrum of an Irishwomac, Thirty-Five Years Old, Exhibit- ing an Unusually Simple inflected i. precentral f . supercentral f. 6 V- central f. J. postcentral f. Sylvian f . 3 parietal f . 4 supertemporal f . paroccipital f. paroccipital g. occipital f. 19 Fig. 776.— Dorso-Caudal Aspect of the Brain of a Fetus Measuring 41 cm. from Heel to Bregma, and Estimated at Eight Months; 734. X 1. 11, Left in- flected Assure ; 12, 13, separate portions of the left postcentral • 14, left parietal (?) ; 16, left parocclpital ; 17, left supertemporal ; 19, left occipital Assure. The remaining numbers indicate Assures of doubtful Identity. Preparation.— Tbe arteries were injected with starch mixture ; extravasa- tion took place at several points, especially the two following: (1) Into the dorsal part of the right occipital Assure, converting it into a kind of fossa, at the bottom of which is seen the unaffected part of the Assure ; (2) into the left paroccipital Assure, separating its walls to some extent. The essen- tial relaUons of parts are not Aected. Condition of the Paroccip- ital Fissure; 386. X .8. Other aspects of this brain are shown in Figs 720 and 721. 1, Subcentral Assure, continuous with the pari- etal, but separated from the postcentral by a con- siderable isthmus; 2, the branch of the postcentral just below (caudad of) the isthmus does not really enter the parietal, al- though the shadow upon the slightly depressed nar- row portion of the isthmus gives that appearance ; 3, an independent Assure parallel with the postcen- tral ; 4, cephalic ramus of the paroccipital ; 5, cepha^ lie stipe of the same ; 6, 7, caudal stipe and ramus; 8, supertemporal; 9, the trlradiate termination of a Assure superAcially con- tinuous with the super- temporal. The name lambdoidal is applied with considerable hesita^ tion. wholly independent of the parietal, although the isthmus (opposite the end of the line from paroccipital) is slightly depressed. B. An unusual di- vergence of the caudal stipe (6) and ramus (7) of the paroccipital ; the former again bifurcates just over the margin on the mesal aspect. 199 Bralu. Brain. REFERENCE HANDBOOK OF THE MEDICAL SCIENCES. C. The presence of an oblique independent fissure caudad of the paroccipital suggesting the persistence of the lambdoidal of the fetus (§ 334 and Fig. 750). D. The separation of the postcentral from the subcen- tral by an isthmus, 3. E. The depth, simplicity, and cephalic trend of the occipital. § 313. Continuity of the Paroccipital with the Parietal Occurs More J § 321. Postpartum Ohanges. — Condition III., bilateral separation, occurs in only 17 per cent, of the total, but cephalic ramus paroccipital isthmus parietal f . zygon f IQ. 779.— The Paroccipifal Bef?ion of Chauneey Wright. On the left, the numbers correspond to those on Figs. 770 and 788. On the right, homologous parts have the same numbers with the addition of prime. and O', the occipital Assures. The left parietal Assure joins the cephalic tamus bf the parocclpital at 2, where there is avadum; on the right the isthmus is narrow and slightly depressed. The fissure marked 36, 37, and 38 is somewhat deep and separated from the occipital by a visible vadum ; on the right (36' i it enters the parocclpital Assure. in 40 per cent, of the five infants. So far as this small number goes there is borne out the conclusion of Cun- ningham that in many cases the union is delayed until after birth. § 333. Mg. 780 illustrates: A. The least common of the four possible combinations of the parocclpital and parietal fissures of the two sides, viz., right continuity and left separation. B. The continuity of the parietal and postcentral fissures on both sides, but with diflferences that are unusual and somewhat perplexing. C. The existence, on the right, of a clearly defined triangular fissure, 3. D. The unusual extension of the caudal Pac. ramus of the parocclpital, 4. p E. The ap^iearance of the trench (6) due to the pressure Of an artery. 6 § 333. Paneto-Pa/roecipital OomMnations in IndimduMls.-r-'Foxn: different combinations are ^ possible (Fig. 778), viz.: I. Left continuity and right separation; 11. Continuity on both Pao. sides; III. Separation on both sides; IV. Left separation iand right continuity. Amongst the 100 individuals tabulated (all that were accessible to nle at the time), combination I. existed in 44; IL in 33; IIL in 17; and IV. in only 6.* § 334. May OomMnation I. (Bight Separa- tion and Left Continuity) be Rega/rded as Nor- mal? — Among the ten educated and moral whites (Group A) combination IV. does not occur (but neither does it among the five murderers). Combination I. occurs in 60 per cent, of Group A, ■ in 48, per cent, of Group B (ignorant- or unknown) ; in 40 per cent, of C (insane), and in 30 per cent, each of D (murderers) and B (Africans). ^ 335. There are manjr questions, general and spe- cial, that arise in connection with the parocclpital, but space permits mention of only two which were briefly discussed in my paper (1900, a): (1) In tabulating should not the cases in which the vadum equals in height more than one-half the greatest depth of the " parieto-paroc- cipital combination" be included under "separation"? (3) What weight is to be assigned to the condition in apes and monkeys where continuity is the rule, perhaps with- out exception? The developmental conditions in other primates than man are not known. § 336. Fig. 781 illustrates: A. The location and common form of the insula. B. The existence of fissures and intervening gyres, radiating in gen- eral from its summit. C. The division of the whole by a somewhat deep fissure, the trans- insular (3), into a cephalic region, preinsula and a caudal, postinsula. % 337. Supergyres and 8ubgyres. — The ectal surfaces of two adjoin- ing gyres are commonly at about the same level, excepting for a marked change in the general con- tour of the cerebrum, as, e.g., at its several margins. But sometimes one gyre may be developed much more than its neighbor, and en- croach upon it so as to conceal it more or less completely. The covering gyre is here called a supergyre, and the covered a sub- gyre. § 338. Superfissures a/nd Subjis- sures. — These terms are employed herein to designate the fissures which result from the formation of super- gyres and subgyres. The line of overlapping of a supergyre is a sniperfissure, as also is the line of junc- tion of two supergyres meeting from opposite direc- tions. A subfissure is one which is concealed by a _ parocoipital f. occipital f . ♦ Mr E. A. Spltzka informs me that this combination exists in the brain of Dr. Edouard Seguin. (See his papers, 1900, o, b.) FIG. 780.— Dorsum of the Occipital Half of the Cerebrum of an Insane Swiss Woman, Fifty-Three Tears Old; 2,964. X 0.6. Her mother was also Insane. 1, A Assure apparently, but not really, connected with the parocclpital ; 2, the cephalic stipe of the parocclpital; 3, a triangular depression; 4, an unusual and deep extension of the parocclpital ; 5, undetermined fissure. On the left, 6, a vascular trench between the parietal and occipital; C, central fissure; Pac., paracentral ; P., parietal ; O., occipital ; Pao., parocclpital. supergyre, and invisible until the lips of the superfis- sure are divaricated. § 339. Nm'mal, human subfissures are the circumin- sular, which encircles the insula (Fig. 783), the transin- sular and others crossing the surface of the insula (Fig. 781), and those which indent the ental or insular surfaces of the operculums (Fig. 783). Unusual subfissures ap- 201 Brain. Brain. REFERENCE HANDBOOK OF THE MEDICAL SCIENCES. pear in Fig. 786, after tile removal of the unusual super- gyre ; superflssures are shown also in Fig. 787. § 330. The insula (" island of Reil ") and the operculum Fig. 781.— EigM Adult Insula, Exposed from the Lateral Aspect ; 480. XI. 1, Cen- tral fissure ; 3, transinsular Assure ; 3, oUactory tract ; i, optic nerve ; 5, optic tract ; 6, cms ; 7, pregenlculum ; 8, postgeniculiim. constitute normal and typical examples of subgyres and supergyres. As may be seen in Figs. 668, 667, 753, and 783, and in the diagram. Fig. 759 (B), the insula is a part of the cortex, which, at one period wholly superfcial, is gradually covered, more or less completely, by con- verging folds of the adjacent regions. The insula thus becomes a subgyre, while the operculum, preoperculum, suboperculum, and postoperculum are supergyres. For other supergyres see §§ 336 and 343. § 331. Mg. 78S illmtrates : A. The exist- ence of two zones of the lenticula, an ectal, the putamen, and a second, entad of the first, as seen in Fig. 739. There is still a third, but it does not extend suflicientlj' far dorsad to appear in this or Fig. 738. B. The constitution of the insula as an elevation of the lateral region of the hemi- cerebrum, its cortex and medulla being con- tinuous with the rest and with the overlap- ping operculums. C. The peculiar form and location of the claustrum, a thin, subcircular disc of cin- erea, between the putamen and the insular cortex, of which it is probably a dismem- berment. § 833. The insula has notable topograph- ical relations with (a) the several oper- culums, (J) the claustrum and lenticula. Altliough perhaps, upon the whole, most developed in man, relatively to the size of the entire brain, it is perfectly distinct in apes and monkeys, in dogs, the porpoise, and many other mammals ; its comparative anatomy and its human variations are fruit- ful and important subjects for further ob- servation ; see especially the papers of E. C. Spitzka (1879, a) and (Clark, 1896). § 333. The Insula in Apes. — According to Cunningham (1897, b, II., 33), he and Marchand have reached independently the conclusion that in apes (orang, chimpanzee, gorilla, and gibbon) only the caudal portion of the insula is covered by the operculum and postoperculum (parietal and temporal operculums), Owihg to the non-development of the other two oper- culums the cephalic portion of the insula is exposed like the rest of the cortex, and the "" sulcus limi- tans " of Reil (part of my clrcuminsular fis- sure) is represented by a " f ronto-orbital sul- cus." • I regret that this interpretation is not borne out by the study I have been able to make of the material at Cornell University. There are more than fifty brains of monkeys and lemurs, and during the past sixteen years I have prepared with special care ten fresh ape brains (one gorilla, three chimpanzee, and six orang); aU have been photographed; some have been sectioned or partly dissected, and one (chimpanzee) has been drawn. Still I hesitate, and am not sure that it will be pos- sible for me to decide until there is available a fetal ape brain displaying the region in question in process of formation. § 834. The operculum is not strictly a sin- gle gyre but includes portions of at least two, the precentrai and the subfrontal. It is as if the eastern half of the southern extrem- ity of Africa were owned by the Dutch and the western by the English, each half having its own territorial designation; we might still speak of the Cape of Good Hope com- posed by the two countries. In general the same may be said of the postoperculum, sub- operculum, and preoperculum. § 335. Mg. 783 illustrates: A. The ex- tent to which the several operculums lap over the insula, constituting so many supergyres. presylvlan t. precentrai t. Sylvian f. thalamus claustrum clrcuminsular f , FIG. 783.— Longisection of the Eight Insula and Adjacent Parts ; 3,397. Enlargement of the corresponding region of Fig. 738. 1, 2, Zones of the lenticula, the lateral and larger the putamen ; 3, the stratum of alba between the putamen and claustrum, sometimes (most undesirably) called " external capsule " ; 4, opposite the clrcum- insular fissure. Internal capsule should be simply eapsula. 202 REFERENCE HANDBOOK OF THE MEDICAL SCIENCES. Brain. Brain. B. The flssuration of the ental surface of the oper- culums. C. The distmctness of the supercallosal fissure, and the absence of a fronto-marginal between it and the dorsal margin of the hemicerebrum. D. The length of the postrhinal Assure, partly con- cealed by the optic nerve. § 336. Subfrontal Mssure and Qyre ("Broea's convolu- tion"). — Prom every point of view, anatomical, histo- paiucentral f . operculum presylvlan f . Sylvian f . postoperculum callosum pulyinar 2 optic tract luppocampal f , preoperculum chiasma optic nerve FIG. 783.— The Mesal Aspect of the Eight Operculums of a Child at Term; 1,823. XI. Preparation.— Tbe hemicerebrum had heen hardened in alcohol while resting on the meson, and hence is a little thinner and wider than natural, but thereby better suited to the desired object. A probe was pushed through from the lateral aspect at the triangular place of divergence of the Sylvian, basisylvian, and presylvlan As- sures ; from the hole so made upon the mesal aspect, cuts were car- ried in various directions, cautiously, until most of the thalamus, caudatum, lentlcula, and insula were removed, thus exposing the ental or mesal surfaces of the operculum, postoperculum, and pre- operculum, with the intervening Sylvian and presylvlan fissures. Defects.— The inclusion of the occipital region would have ren- dered the -figure somewhat more intelligtble. The suboperculum and subsylvlan fissure are not exposed ; toe cut surface at the ven- tral side should be traversed by a line starting from just cephalad of the chiasma to represent that part of the basisylvlan fissure. logical, physiological, psychological, anthropological, and zoological, a most interesting and important cortical region is that which Broca first showed to be related to the faculty of articulate speech. Although the condi- tions are often, perhaps usually, complex and perplexing, there seem to me to be a sufficiently large number of cases like those represented in Pigs. 663 and 784 to warrant de- scribing the gyre as curving about the presylvian fissure, and the fissure as zygal and U-shaped; the topography is much like that of the FIG. 784.— Left Subfrontal Gyre (" Broca's Convolution ") and Adjacent Parts of a Man about Thirty-Three Years Old. X .5. He was the son of a clergyman, hut was found dead after a drunken debauch. paroccipital fissure and gyre. § 337. Fig. 784- il- lustrates : A. An un- usually simple condi- tion of the subfront- 1- presylvian f. al gyre as a U-shaped operculum ^gion about the pre- sylvian fissure. B. An unusually simple zygal form of the subfrontal fis- sure, comparable with that in the in- fant brain shown in Pig. 663. O. The complete separation of the sub- frontal Assure from medifrontal f. (?) precentral f . subfrontal f. subfrontal g. preoperculum Insula subsylvlan f. the precentral and the bifurcation of the latter at the point reached by the line from the name. D. The relatively large size of the preoperculum as compared with the suboperculum ; these proportions also are as in Fig. 663, and the reverse of those in Pig. 752. E. The (probable) partial exposure of the insula in the adult brain. § 338. The Subfrontal Gyre in Apes. — A paper on this subject has been published by Herve (1888). I am not prepared to discuss Herve's conclusions as to the degree of representation of the subfrontal gyre in apes ; but I am compelled to dissent from the statement (p. 22) that of the two branches of the Sylvian fissure " as- cending" and "horizontal" (corresponding re- spectively to my presylvian and subsylvian) the latter is the more constant. § 339. Recalling my own earlier erroneous interpretation of the parts, I am compelled to insist upon the necessity of exposing them fully by removing the postoperculum, and of deter- mining whether or not a given fissure cuts through the entire thickness of the operculum. § 340. Supergyres and subgyres occur by ex- ception in other parts of the cerebrum, espe- cially the occipital (see Pigs. 785 and 786), and normally in many monkeys, the poma, § 351, Fig. 787. I 341. Figs. 785 ami 786 illustrate : A. The presence of a postcuneal Assure along the cau- dal margin of the cuneus ; its dorsal end is free, but ventrad it has a very shallow connection with the calcarine. B. The concealment, in the undissected brain, of the convexities of the paroccipital Assure and gyre and part central f. postcen- ( 6 ^*^'^ central f . paracen- tral t. postcen- tral t. subtem- poral calcarine f. Fig. 785.— Dorso-Candal Aspect of the Left Hemicerebrum of an Adult Male Mulatto ; 322. X .8. 1, Nearly straight fissure along the cau- dal margin of the cuneus, the postcuneal f . (?) ; 2, unidentified oc- cipital f . ; 3, margin of a supergyre overlapping the paroccipital fissure, part of the paroccipital gyre, and the lateral end of the oc- cipital fissure ; 5, near the margin of the same supergyre ; 6, ventral part of the postcentral f. The interrupted L-shaped line from op- posite 1 to the middle of the length of the parietal fissure indicates the lines of incision by which the supergyre was removed, as seen in Fig. 786, where the two fissures are commented upon (see § 341) . For the preparation, see Fig. 757. of the occipital Assure by an extensive supergyre, anal- agous to, though probably not homologous with, the poma (occipital operculum) of monkey brains (Pig. 787). C. The conversion of the paroccipital Assure and gyre into a subAssure and subgyre. D. The apparent continuity of the exoccipital with the occipital in the undissected brain. 203 Brain. Brain. REFERENCE HANDBOOK OF THE MEDICAL SCIENCES. E. In general, the desirability of checking all con- clusions based upon the obvious features of the cerebrum, by an examination of the concealed conditions. § 343. The so-called "external occipital," or "external perpendicular," fissure of monkeys is a superflssure. exoccipital f. Fig. 788.— Dorso-Oaudal Aspect ot the Left Hemieerebrum ol an Adult Male Mulatto, Partly Dissected ; 323. X .8. 1, Junction of tlie parietal and postcentral Assures ; 3, a Assure connected with the ex- occlpltal. Prejpwration. — By two Incisions along the L-shaped line shown in Fig. 78B the supergyre there indicated by 3 and 5 has been re- moved. factitious, variable, and heterogeneous, resulting from the lapping of a supergyre, the poma (" occipital oper- culum "), upon the parts cephalad of it ; it may therefore be called the pomatie fissure. § 343. Fig. 787 illustrates: A. The relation of the poma (" occipital operculum ") of monkeys, as a typical supergyre, to the paroccipital and part of the supertem- poral, which are here subgyres. B. The relation of the pomatie ("external occipital") fissure of monkeys, a typical superflssure, to the paroc- cipital and occipital fissures, which are here wholly or partly subfissures. C. The, so to speak, factitious nature of the pomatie fissure, since it results, not from the opposition of two adjoining and approximately equal gyres, but from the lapping of one over the crests of those adjoining. As may be seen by comparing the two sides, it really comprises three distinct parts, viz. , a lateral, between the pomatie margin and the ectal surface of the temporal gyre ; an intermediate, coinciding with the cephalic stipe of the paroccipital fissure; a mesal, formed by the pomatie margin and the paroccipital gyre ; finally, since the dorsal termination of the occipital fissure is covered by the poma, there results an apparent continuity of the pomatie and occipital fissures. D. The continuity (depth not determined) of the paroc- cipital fissure with the parietal; see g 335. E. The junction of the Sylvian and supertemporal fissures. F. The distinctness of the "angular gyres." G. The existence of peculiarities and complexities which, in my judgment, render monkey brains less ser- viceable than those of human fetuses for the elucidation of fissural problems. § 344. Under the various titles " external perpendicu- lar," "external occipital," "temporo-occipital," "ape- fissure," "vordere occipital," etc., have been included several difEerent human fissures or combinations of fis- sures, viz. : (A) The dorsal outcrop of an unusually deep occipital fissure ; Marshall, "The Brainof aBushwoman," Philosophieal Transactions, cliv., p. 511, Figs. 1, 9, h; (B) a fissure on the lateral aspect caudad of the supertem- poral, and having a general dorso-ventral direction ; the wrdere occipital oi Wernicke ("Das Urwindungssystem des menschlichen Gehirns," Arch, fiir PsycUatrie, 1875, pi. v.. Pigs. 19 and 33, k); called exoeeipital in the present article in order to avoid usin^ the more natural mononym, pi-eoccipital, already applied elsewhere by Meynert; (C)the combination of A and B,* on account of a supergyre which covers the dorsal end of the true occipital fissure (A) and permits the adjacent end of B apparently to become continuous with it, as in Figs. 785 and 786. § 345. No one of the fissures or fissural combinations mentioned in § 344 is identical with the pomatie fissure of most monkeys ; but the exoeeipital may exist in the true apes and in Ateles (Huxley, Zool. Proe., 1861, pi. xxix. ). It is doubtful whether the term " ape-fissure " is a desirable one to retain, f § 346. What Significance Has tlie An-angement of the itssures? — The query is warranted by two classes of facts, viz. : (1) with the mammals whose cerebrums are fissured a more or less definite fissural pattern has been recognized in most of the species studied in that respect; .. .central £. ...parietal f. ■ • Sylvian f, j supertem- I poral f . paroccipital £. .. occipital f. paroccipital g. poma 6 2 1 poma pomatie f. Fig. 787.^Dorao-Caudal Aspect of the Brain of a Monkey (Maeaeus), the Kight Poma Lifted; 1,807. XI. 1, Caudal end of right occipital lobe ; 2, surface caudad of poma ; 8, unldentifled Assure ; i (Ught line), line of detachment of the pomatie margin ; 5, superAssure re- sulting from the union of the Sylvian and supertemporal ; 6, post- central (?) f . ; 7-15, undetermined frontal Assures ; 16, left central f. ; 17, left parietal f.; 18, left postcentral (?) f. ; 19, left Sylvian f. ; 20, left supertemporal f . ; 21, Assure on the mesal surface of the oc- cipital lobe, seen also on the right. Preparation. — The fresh brain was exposed in brine, and left In the base of the skull for support ; on the right side, the margin of the overlapping poma (" occipital operculum ") was freed by tearing the arachnoid with the syringotome (see article Brain: Methocis), and the poma reverted and kept In position with absorbent cotton wet with brine. The whole was then placed in 95 per cent, alcohol so as to harden rapidly in the desired shape. When Arm It was photographed from the dorso-caudal aspect, the lifted poma being greatly foreshortened. The parts on the left were undisturbed. (3) the fissures of idiots are commonly peculiar in some way. There is, therefore, no reason, a priori, why one should not seek fissural correlation with sex, family, race, capacity, attainment, and character. § 347._ Some idea of the problems involved and the dimculties of their solution may be gained from the com- * " The so-called ape-flssure has been so termed because it Imitates in disposlti'oti the opercular [my pomatie] Assure ot the apes. It is, however, not a perfect homologue of that Assure, though its presence, when it Is due to the fusion of the external occipital vrtth the Internal perpendicular sulcus, is a slgnlAcant sign of disturbed cerebral growth " (E. C. Spltzka, " Insanity," 1887, 286) . + For some years I have been gathering materials for the elucidation of one of the most perplexing subjects In cerebral topography, the so-called "ape-Assure," but this Is not the occasion for a full pr^enta- tlon of either facts or opinions. 204 REFERENCE HANDBOOK OF THE MEDICAL SCIENCES. Brain. Brain. parison of the cerebrums of the two philosophers, Wright and Oliver, the Swedish carpenter, and the unknown mu- latto (Figs. 664, 763, 767, 770, and 788). The first two differ markedly not merely in detail but in general aspect; architecturally speaking, the gyres of Oliver are Corin- thian in style, those of Wright, Egyptian. An approxi- mation to this is seen in the mulatto. The mechanic's cerebrum is fissured to an unusual degree and the insula completely hidden ; the philosopher had a larger brain, but its lateral aspect presents an equally unusual absence of flssural complexity and the insula is exposed. § 348. Comments upon Mg. 788. — Pending the detailed Study and description of this very interesting brain by the writer, to whom it has been generously loaned from the Museum of Harvard Medical School, with the consent of its preparator and first describer, Dr. Thomas Dwight, the professor of anatomy, the following points may be noted: A. The great length of this hemicerebrum as compared with that of the mulatto (Fig. 762). B. The special length of the caudal part, whether the central or the Sylvian fissure be taken as the dividing line. C. The height of the frontal region. D. The apparently slight extent of the prefrontal lobe ; a/ppa/rently, because, as is shown upon the dorsal aspect (Fig. 770), a large part of this region is invisible from the side, and is of unusual width. E. The simplicity of the visible gyres, due to the few contortions of the main fissures, and the comparative infrequency of minor ones; msible. because the unseen cephalic surface of the prefrontal lobe presents a much greater complexity. F. The condition of the minor fissures as sharp incisions rather than as slight depressions, like those in the Swe- dish bram (Fig. 767). G. The visibility of the insula, at least equal to that in the mulatto (Fig. 7.63). Whether any of this condition sapercentral f. central f . precentral subfi '>at il is due to the pressure during hardening which may have occasioned alsoa peculiar roundness of the temporal lobe, it is impossible to determine, and Dr. Dwight does not recall the condition of the parts when the brain was re- moved. H. The great length of the supertemporal fissure, and its dorsal subdivision. I. The bifurcation of the Sylvian fissure, constituting perliaps an episylvian and hyposylvian as in the mulatto. J. The complete independence of the precentral and subfrontal fissures. K. The union of the proximal parts of the presylvian and subsylvian fissures, so as to separate the pre- and postoperculum, L. The presence of an unusual, curved fissure (14) ventrad of the subcentral. M. The crossing of the temporal region ventrad of the supertemporal fissure by several irregular fissures (trans- temporal). N. The complication of the zygal form of the orbital, fissure by a branch extending cephalad from the middle of the zygon. O. The complete interruption of the central fissure by an isthmus which is more clearly indicated in Figs 770 and 771. P. The fulness or " plumpness " of the gyres, remarked by Dr. Dwight. § 349. Is There a Criminal Type of Maswes ? — Bene- dikt and others have held that, in murderers for example, there is a tendency to flssural confluence or to a condition resembling that in certain camivora. The materials at my disposal lead me to share the doubts expressed by Donaldsoh {Amer. Neurol. Transactions, 1893, p. 54), Sohwekendiek (Amer. Jour. Neurol, ancl PsyeMatry, i., 569-573), and Schafer (" Quain "), 1893, 161. Upon the whole, notwithstanding the able contributions of Dercum (1889, 1893), Mickle (1896), Mills (1886), Weinberg (1896), nnstn/^TifT'n.l f _ Olfactory f . i baslsylvlan t. Pig. 788.— Lateral Aspect ol the Left Hemicerebrum of Chaunoey Wright, a Distinguished Philosophical Writer, who died in 1875 at the age of ^'"^P^emaraUon —The brain was removed with care (in the usuai way) and hardened in zinc chloride ; there seems to have been consid- ..rnhlB dorso-ventral sinking and lateral spreading. In the absencejof a oast or measurements of the cranial cavity, it is of course Impossi- hlP to aav how extensive this distortion has been ; enough, probably, to account for the flatness of the dorsal surface, and the consequent wShortenine of the Assures of that region as seen from the side, but not sufHoient to have produced the great width of the prefrontal inhM noted under Fig. 768. The figure accompanying Dwight's suggestive remarks upon this brain (Ameiriean Anadenmi Proeeedings, ]8Wr»lS-, PP- 210-315) is stated to be somewhat diagrammatic, largely, apparently, for the sake of exhibiting the entire lateral aspect to better advantage. 205 Bralu. Brain. REFERENCE HANDBOOK OF THE MEDICAL SCIENCES. Wilmarth and others, I am disposed to regard as premature any conclusions as to fissural correlation, and to urge re- newed and systematic efforts in three directions, viz. : (1) The determination of the standaidflssural pattern for the average well-born, orderly, and educated white male ; (3) the collation of the conditions in large numbers of individuals of the other sex, of other races (especially the African), and mental and moral conditions; (3) the detailed de- scription and portrayal of the Assures of individuals of marked characteristics. § 350. The Yalue of Organization. — In France there has existed for many years a "Societe mutuelle d'Autopsie." In 1890 was formed the American Anthropometric Soci- ety, which has already received the brains of Harrison Allen, Edward D. Cope, Joseph Leidy (its first president), of his brother, Dr. Philip Leidy, and Dr. James W. White. I had already prepared a " Form of Bequest of Brain " which was first executed in 1889, and which, as since amended, is here reproduced : FOEM OF BEQUEST OF BEAIN. I, , now ol student of from to and graduated from in , recognizing the need of studying tlie brains of educated and orderly persons rather than those of the ignorant, criminal, or insane, In order to determine their weight, form, and fissural pattern, the correlations with bodily and mental powers of various Icinds and degrees, and the influences of sex, age, and inheritance, hereby declare my wish that, at my death, my brain should be entrusted to the Cornell Brain Association (when that is organized) or (pending its organization) to the curator of the collection of human brains in the museum of Cornell Univer- sity, for scientlflc uses, and for preservation, as a whole or in part as may be thought best. It my near relatives, by blood or by marriage, object seriously to the f ulBlment of this bequest, It shall be void ; but I earnestly hope that they may interpose neither objection nor obsta^ cle. I ask them to notify the proper person promptly of my death ; If possible, even, of its near approach. Signature Date Witness Notes.— 1. A duplicate copy of this form should be filled out and retained by the testator. 2. The bequest should be accompanied by a photograph and a sketch of Ufe or character, or a reference to published biography. 3. Tbe testator should give notice of any change of address, not merely on account of the bequest, but also In order that copies of circulars or other publications may be sent. 4. A brain is safely transmitted In a tin pail of some liquid of nearly its own specific gravity (about 1.04) in which it will just float without either pressing on the bottom or rising above the surface. The most readily prepared is nearly saturated brine, made by dissolving in wa- t«r as much common salt as it will dissolve, then pouring it oft, and adding a little water till the brain is just suspended. Preservation as well as safe transportation may be assured by adding sufficient salt to water containing three, four, or five parts of commercial (forty per cent.) formalin.* 5. The lid of the pail should be secured with surgeon's adhesive plaster ; the pail should be addressed as follows : Anatomical De- partment, Cornell University, Ithaca, N. T. Specimen of Natu- ral History. Perishable. 6. Copies of provisional diagrams of the fissures will be mailed upon application. For a statement of reasons tor the study of the brains of educated persons, see Buck's Eefeeenoe Handbook of the Medical Sciences (Wm. Wood & Co., New York), VIII., 163, and IX., 110. Besides the nine named in § 315 whose brains have already come into our possession, the " Form" has been filled out by more than fifty, including undergraduates, alumni, and teachers in this and other institutions of learning. § 351. TTie Public aTiould be Educated in This Respect. — Prom the physiological and psychological standpoint it is clearly desirable to study the cerebrums of persons whose mental or physical powers were marked and well known, f The present condition of things is illogical and unprofitable. We scrutinize and record the characters and attainments of public men, clergymen, and friends, whose brains are unobtainable. We study the brains of * For other liquids adapted to the transportation and preservation of the brain, see the article. Brain : Methods. t Among the Individuals best adapted to subserve this object are college professors, who have usually somewhat sharply defined capac- ities and attainments, and are the subjects of prolonged and discrim- inating observation and discussion among their trustees, colleagues, and students; no professor's brain should be lost to neurological science. paupers, insane, and criminals, whose characters are un- known or perhaps not worth knowing. It is at once a reproach and an irreparable loss to science that the community has not yet been convinced that the preservation and study of one's brain is an honor to be coveted. Who can set a limit to the results that might have been attained from the examination of the brains of soldiers like Grant, Sherman, and Sheridan ; of preach- ers likeBeecher, Brooks, and Howard Crosby; of natural- ists like Agassiz, Gray, and Jeffries Wyman ; of lawyers like Tilden, Conkling, and Benjamin Butler? Hov? long must science wait for a general sentiment such as is em- bodied in the declaration of an eminent historian, that science is as welcome to his brain as to his old hat, and that he wislies he had ten of them?* I 353. Brain Weight.— This interesting topic is dis- cussed from the human side In the article Brain, Growth of tlie, but a few words may be added here as to com- parative weight, f § 353. In absolute weight the human brain is exceeded by those of whales and porpoises (3,365-3,171 gm., 5-7 pounds) and of elephants (4,530 and upward, 10 pounds or more). The lowest of these figures approximates the greatest weight claimed for a non-hydrocephalic i human brain. A negro brain described by Dr. C. Tompkins, Virginia Med. Monthly, January, 1883, pp. 391-393, weighed 1,983.80 (70 ounces or 4 pounds 6 ounces). Van Walsem has described {Neurologisches Gentralblatt, xviii.. No. 13, 1899) the brain of an epileptic idiot which weighed, when fresh, 3,850 gm. (90 ounces, or 5 pounds 10 ounces) ! § 354. But in no animal other than those mentioned above is the brain as heavy as the smallest human, viz., that of aBushwoman, 871 gm. (30.75 ounces). In a bull it was 387 gm., in a lion, 198, and in an adult gorilla only 435(15 ounces) (Owen, iii., 144). The largest ape brain is then only half as large as the smallest normal human. § 355. The relative weights of the body and brain vary greatly according to the condition of the former at death. Most of the cases tabulated were of persons dying after more or less prolonged disease, and the figures are as fol- lows: for 81 males, 1 to 36.50; for 83 females, 1 to 36.46; according to Bischoff, 1 to 35.30. Quain concludes that in healthy individuals dying suddenly from disease or accident, the ratio is probably about as 1 to 45. In com- paring man with animals in this respect this last ratio should commonly be adopted. § 356. Owen estimates the adult male gorilla at 300 pounds, or 90,730 gm., and the brain would be as 1 to 313; in a bull it was as 1 to 3,000, and in a lion as 1 to 555. On the other hand, in a sparrow the ratio was as 1 to 35; and in a marmoset {Midas) 1 to 30 (Owen, iii., 143); and in Jacchus tmlga/ris (No. 664, Cornell Univer- ity Museum), as 1 to 19. But it is to be noted that in these small monkeys, as in birds, the cerebrum is not fissured. Perhaps the least misleading mode of stating the case is to say that the human brain is relatively heavier than that of any animal larger than a cat in which the cerebrum is fissured. VIII. Rhinencephal.— § 357. Olfactory Bulb and Tract. — These parts of the human brain have already been shown from various aspects in Figs. 663, 670 673 689, 751, 753, and 765. In Fig. 789 they present almost diagrammatic simplicity as a tongue-like extension from the region of the postcribrum ("anterior perforated space ") more or less completely covering the olfactory fissure. * It Is encouraging to know that the brain of the late George Grote, historian of Greece, has been described by John Marshall in the Jour, of Anat. and Physiol., vol. xxvli., pp. 21-68. + The two papers of Waldeyer (1896) contain the titles of six hun- dred and thirty-seven books and papers relating to Assures, gyres, commissures, and brain weight, and published, for the most part, be- tween 1879 and 1898. t The brain of a Chippewa Indian squaw, eighty-flve years olll, rach- itic, in the Army Medical Museum, Anatomical Section, No. 1,031, weighed when fresh 73.5 ounces (2,083.72 gm.), but it was hydroeeph^ alic, and the curator informs me that tbe ventricular liquid was probably included in the weight." 206 REFERENCE HANDBOOK OF THE MEDICAL SCIENCES. Bralo. Brain. § 358. Mg. 789 illustrates: A. The length of the olfactory bulb at this period, as compared with its tract, which latter is the longer in the adult. B. The concealment of the entire olfactory Assure by the olfactory bulb ; in the adult, usually, the fissure pro- jects considerably beyond the bulb (Fig. 672). C. The apparent continuity of the insula with the lateral root of the olfactory tract. D. The partial covering of the insula at this period. E. The thickness and roundness of the margin of the operculum. F. The formation, at this period, of the presylvian fissure, constituting the cephalic limit of the operculum, but the non-existence of a subsylvian fissure. § 359. The corresponding parts in several other verte- brates are shown in Figs. 680 (turtle), 685 (frog), 717 (salamander), 682 and 686 (cat), and 688, 726, and 794 {sheep). Any remnant of the former anthropotomical idea that the olfactory tracts and bulbs constitute merely the first pair of cranial nerves * will probably be dispelled frontal lobe olfactory bulb — olfactory tract— Fig. 789.— Ventral Aspect of tbe Left Hemlcerebrum of a. Fetus, Size and Age Unknown ; 1,820. X 1. The lateral aspect of the same preparation Is shown in Fig. 751. by noting the relative extent of the corresponding parts in still lower forms, the lamprey (Fig. 790) and the hag (Fig. 791). § 360. Mg. 790 ilhistrates : A. The representation of all the six definitive segments in this lowly vertebrate ; the mesencephalic lobes (geminum) are prominent ; the cerebellum is small and was removed with the rest of the roof. B. The preponderance of the olfactory bulbs over the lateral masses presumably representing the cerebral hemispheres. C. The concomitantly large size of the lateral portion of the rhinocele. § 361. Mg. 791 illmtrates: A. The most distinctive character of the myxinoid brain, i.e., the insignificance of the intermediate region represented in most vertebrates by the more or less prominent cerebellum and quadri- geminum ; hence the entire organ naturally divides itself into a caudal portion, the oblongata, obviously an en- largement of the myel, and the brain proper, comprising four pairs of lobes narrowing caudad. B. The large size of the olfactory bulbs, especially as seen from the ventral side. C. The continuity of the olfactory bulbs across the meson, as seen from the ventral aspect. D. The unusual location or trend of the mesal body pro- * For the present It will probably prove convenient at least to avoid modification of the accepted numerical designations of the heterogene- ous cranial nerves by regarding as the ' first pair " the nervous flla^ ments which connect the olfactory bulbs with the na^l mucosa. visionally named "epiphysis or dorsal sac," viz., nearer the cephalic than the caudal limit of the segment inter- preted as the thalami or diencephal. E. The vagueness of certain features due to the imper- fect condition of the specimen. It was prepared by me in 1875 and the membranes, in- cluding the meta- tela. prematurely removed. There has not been time to prepare an- other, and the published ac- counts'and figures do not clear up all the doubtful points. § 362. Bhino- cele. — In verte- brates generally {e.g., the lamprey. Fig. 790) and in most mammals (e.g., the sheep. Fig. 792), the ol- factory bulb and crus contain a cavity, the rhino- cele, continuous with the paracele and united with its opposite across the meson by the aula. Strictly and by analogy rhinocele should apply to the entire cavity of the rhinencephal, but for the pres- ent it is at least convenient to employ it also for either lateral portion. § 363. The development of the olfactory portion of the brain varies so greatly among mammals that Broca, Turner, and others have proposed groupings based there- on, viz., inio maorosmaiic, e.g., the armadillo; mierosmatic, e.g., man and apes; and miasmatic, the porpoise, where the olfactory tract and bulb seem to be wholly absent, although the early .,,„,,,,„ f V ! rfiinenceptal- prosencephal diencephcd mesenceplial. epencephal metencephal myel metacele myelocele- FIG. 790.— Diagram of the Brain of the Sea- Lamprey, Petromyzon ma/rinus, as if the roof of the cavities was removed : enlarged. It is based upon several preparations made by me in 1874, and would be changed in some respects if made from microscopic sections ; but the main features are believed to be accurate. fetal conditions are not known. The conditions in dogs are peculiar, as appears in the following ab- stract of P. A. Fish's paper, 1891: 1. The facts do not warrant Broca's statement as to the existence of a true ventricular axis (core of solid material in place of the primitive cavity) in the olfac- tory bulb, even in rat-terriers. 3. The bulb is not completely but par- tially occluded, or perhaps in process of becoming entirely so. 3. The cavity of the tract, in some wild forms as well as domestic, is com- pletely closed, there- by cutting off all communication b e- tween the paracele and the cavity of the bulb. 4. The acuteness of the sense of smell is ( olfactory bulb I (rhincephal) f "hemisphere" I {prosencephal) ( epiphysis or I dorsal sac (?; thalamus (diencephal) geminum imesencephal) metacele ( oblongata 1 (metenceplial) myel commissure (?) 1 Fig. 791.— Dorsal (Upper) and Ventral (Lower) Aspects of the Brain of the Hag, BdeUoetmm ; 212. X 2.5. 207 Brain. Brain. REFERENCE HANDBOOK OF THE MEDICAL SCIENCES. not essentially dependent upon the relative size of the rhinocele. 5. Atrophy is not a necessary concomitant of occlu- sion. 6. Domestication, and the consequent disuse" of olfac- tion as a means for procuring sustenance, may be a factor in promoting occlusion. 7. In the classifications of Broca and Turner the dog seems to hold an anomalous position, in that he gives every external evidence of macrosmatic power ; but by the almost total occlusion of his rhinocele he approaches structurally the conditions found in the microsmatics. Physiologically he is macrosmatic ; morphologically he is microsmatic. g 364. JPreeommissure. — As stated in §§ 45 and 310, this fibrous bundle, single at the meson, soon divides into a cerebral portion {pars temporalis) a.nA an olfactory (pars olfactoria). The gross relations of the two are well shown in Fig. 793. For the microscopic arrangement of this and other fibrous constituents of the olfactory apparatus see the article Brain, Histology of the. § 365. Fig. 792 illustrates : A. The divei-gence of the olfectory and cerebral divisions of the precommissure just laterad of the meson. B. The relatively large size of the olfactory division in the sheep. 0. The large size of the rhinocele, but the narrowness of the strait connecting it with the precomu. § 366. Crista. — In the cat, adult as well as fetal, the caudal ■ or celian aspect of the terma, between the columns of the fornix, presents (Fig. 686) a mesal hemispherical rhinocele strait precomu caudatum septum pars olfactoria precommissure aula pars temporalis medicommissure paraplexus medicomu hlppocamp erus pons cerebellum trapezium pyramid Fig. 792.— Brain ot Sheep Dissected to Show the Two Divisions of the Precommissure ; 2,653. X .9. Prepared by P. A. Fish. The cere- brum was cut from the ventral side in two planes meeting at about a right angle along the line indicated by the shadow just caudad of the line from the word medicommissure. The cephalic slope was then very carefully sliced to a deeper level, so as to leave the pre- commissure in relief. Unfortunately the pars nlfactiyria on the left (right of the picture) has since been broken, accounting for the interruption In the flgure. Just within the aula may be dimly seen the crista. Compare with the medlsected brain (article, Brain : Methods^, and that of the cat (Fig. 686). body which is translucent when fresh. In some lower vertebrates it seems to be represented by a membranous mass. It has been observed in comparatively few forms, and its structure, connections, and significance are unde- termined. I have never seen it in adult human brains, but it is perfectly distinct in the preparation represented in Fig. 793. If there is a rhinencephalic segment the crista is to be regarded as one of its constituents. § 367. Fig. 793 illustrates: A. The presence of the crista in a child at term. B. The dorsal limitation of the aula and the two portas by the line of reflection of the endyma constituting a ripa. C. The narrowness of the body of the fornix as com- pared with that of the cat and most other mammals. D. The division of the caudo-ven- tral surface of the fornix, by the ripa mentioned under B, into an entocelian area, covered by en- dyma and forming the cephalic wall of the aula and the two portas, and an ectocelian area, cov- ered by pia. the dorsal or fornical layer of the velum. I 368. riie V/m'd Bhineneephalon in Several 1. — Some con- fusion may be avoided if it is clearly recognized that one and the same word has at least live diiferent significations. 1. Owen applied rhinencephalon t o the two olfactory bulbs and their tracts (or crura) without apparent reference to any mesal or connecting constituents.* 3. Turner pro- posed (1890) to re- gard the prosen- • cephal as divided horizontally by the rhinal Assure (olfac- tory and postrhinal) into a ventral portion, the rhinence- phalon, and a dorsal, the pallium. 3. Shafer proposed (Quain, 1893, 160) to include under rhinencephalon the remainder of the so-called "limbic lobe" (the hippocampal gyre), and the callosal or '^ gyrus fornicatus. " f 4. His considers (1893) that the bulbs and tracts, the precribrums ("anterior perforated spaces") and some other parts, under the name rhinencephalon, constitute one of three components of the dorsal zone of the most " anterior " segment, which he names telericephalon. This view has been adopted by the Anatomische Uesellschaft and is indicated in the Table in the article, Brain, Devel- opment of; see also my Table I. 5. In the report of the Committee on Anatomical Nomenclature which was adopted by the Association of the American Anatomists in, 1897 {Proceedings, p. 47) the rhinencephalon was regarded as a definitive segment consisting of the olfactory bulbs and tracts and some other parts united across the meson by the pars olfactoria of the precommissure, the lateral cavities being connected * The mesal contact or coalescence of the bulbs in frogs and toads, and (as observed by Mrs. Gage, 1895) in certain turtles and birds, is a secondary condition that has no bearing on the segmental constitution of the parts. * Since the name and notion of a " lobus lianbicvs " seem to be sometimes adopted without adequate inquiry, I cannot refrain from pointing out that, as Is clear in Shafer's diagram (Fig. 109), its alleged boundaries are not continuous in man, and I am not aware that they are in any animal. Fig. 793.— The Crista and Adjacent Parts of a Child at Term ; 4. X 1.5. Preparatton..— Alter ' transection at about the middle of the diacele, the thai- ami were torn from' their continuity with ' the fornix, leaving the Irregular surface- at and ventrad of 1. The lateral parts- were tben removed, as indicated in the drawing. The paraplexus was torn from the margin of the fimbria, constituting the lateral part of the fornix ; the short- line at the right ascends from the fimbria, crossing the intervening space; paracele. On the left the similar line begins more nearly at the middle of the fornix, and crosses first the callosum itself, and then the callosal fissure. Before photograph- ing, the crista was touched with white paint. Defects.— Ths brain was ill preserved, and broke apart during dissection ; the shading is too heavy. 208 REFERENCE HANDBOOK OP THE MEDICAL SCIENCES. Brain. Brain. by the mesal aula. The other constituents of the rhin- encephal are named in Table I. (See above § 713). § 369. CormnentaHea on Mg. 794. — Besides facilitating the recognition of certain important parts and their rela- postoWongata Fig. 794.— Left Side of the Sheep's Brain Alter the Removal of Portions of the Cere- brum and Cerebellum, So as to Display the Segmental Constitution of the Organ. (From '■ Physiology Practicums " ; compare Fig. 688.) 1, 3, Olfactory tract ; 2, a part of the palUum which has not been cut ; 4 (indistinct), chiasma; 5, pregeniculum (external or anterior geniculate body), distinct In man but here little more than a lateral portion of the thalamus ; 8, tuber (ctoereum), the slight convexity to which the hypophysis is attached; 7, medipeduncle ; 8, trapezium. The short lines on the surface of the olfactory bulb represent the olfactory nerves. The cut end of the left optic nerve is dotted to indicate its fibrous structure. Excepting the unshaded areas, representing cut surfaces, all the parts seen in this figure were covered by pia. PreparaMon. — The cerebellum is left of its natural height, but the cephalic and caudal convexities are sliced away so as to expose the parts which are over- hung by them. The cerebrum has been cut down to the level of the thalami ; the caudal portion cut away along the oblique line of its projection over the part marli^ed 5 ; the lateral portion so as to expose the part marlced 3 ; also the cephalic projection which overhangs the olfactory bulbs. tive positions, this figure well illustrates the segmental consUtution of the brain, which is obscured in the entire organ by the preponderance of the cerebrum and cere- bellum. There is a series of more or less distinct masses demarcated by constrictions of greater or less depth. Admitting that there is still some doubt as to number and limits of the segments, the following assignments may be accepted provisionally : Olfactory bulbs and tracts }- bhinencephal. Cerebrum )■ phosencephal (fore-brain). Thalami, epiphysis, hypophysis, ) diencephal chiasma, and geniculums j (inter-brain). Geminums and crura y mesencephal (mid-brain). "^"ISon^gat^ '''' \ —cepha. (hind-brain). Postoblongata y MEXENCEPHAii (after-brain). See the fuller Table on page 153. § 370. Is there a Bhinencephalie Segment? — That lam at present disposed to answer this question in the aflBrm- ative is indicated in diagrams (Figs. 674 and 675), Tables (I. and II.), and remarks (§ 45) in the earlier part of this article; see also Figs. 790, 791, and 794. The whole sub- ject is still under discussion and likely to be for some time to come, and this is not the occasion for detailed argument. There may be stated here, however, three facts that may not be familiar to all students of normal human anatomy : 1. In the lamprey and hag, although the olfactory bulbs are paired, the olfactory sac and nostril are single and mesal. 3. In the lancelet (AmpMoxms or BrancMostoma) the olfactory bulb is single and approximately mesal, al- though, like several other organs of this peculiar verte- brate, not quite mesal. 3. In the malformation called monophthalmia or Vol. II.— 14 cyclopia (see Fig. 713 and the article Teratology), not only the cerebrum but also the olfactory portion of the brain may be single and mesal. A very instructive case is described and figured by Cunningham and Bennett, Royal Irish Aead. Trans., xxix., 101-183. § 371. Limits of the BhinencepMl.— These were not defined in the report adopted by the A. A. A. , and cannot yet, perhaps, be deter- mined with accuracy. But as an individual I may here express the opinion that in mam- mals the caudal boundary coincides practi- cally with the origin of the medicerebral (" middle cerebral ") artery, or with the place of junction of the Sylvian fissure with the "rhinal," including by this the olfactory and the postrhiual (amygdaline) together. This leaves the tip of the temporal lobe, the lobus hippocampi, and the whole hippocampal gyre as parts of the prosencephalic pallium, al- though they may contain the cortical centres of the olfactory sense. In the lower mammals, the elevation sometimes called protuberantia natiformis similarly lies caudad of the rhinen- cephalic boundary. § 373. Postrhinal Fissure — Although re- garded as lying within the pallium and thus in the prosencephal rather than the rhinence- phal its associations are such that a few words may be added here as to its apparently differ- ent locations in man and in the lower mam- mals. In the latter both it and the olfactory fissure are visible from the lateral aspect. But in the lower monkeys the greater de- velopment of the pallium crowds them to the ventral side, and in man and apes the postrhinal fissure becomes actually mesal (Figs. 765, 766). IX. Meninges (the Envelopes ok Mem- branes OF THE BkAIN and SpTNAL CoRD). — § 373. Definitions. — Meninges is the plural of meninx, from the Greek fi^viy?, signifying any membrane cr coating, as of the eyeball, and even the scum upon milk or wine ; but, as stated by Hyrtl (" Ono- matologia," p. 334), the word was restricted by Aris- totle ("Hist. Anim.," lib. i., cap. 16) to the coverings of the brain (and myel?), and the limitation has been since maintained. The synonyms of meninx are: Fr., meninge; It. and 8p., m,eninge ; Ger., Hirnhaut. § 874. Ths Three Meninges. — Nearly all anatomists recognize three chief membranous envelopes between the substance of the neuron (brain and spinal cord) and the craniospinal canal, viz.: an ental, the pia; an ectal, the dura; aamtermediate, the a/rachnoid. Their relative positions when the cranium is opened are indicated in Figs. 795 and 796. Properly speaking the pia pertains to the neuron, and the dura to the craniospinal canal, while the arachnoid has more or less varied relations to both the other meninges. All three present differences according to their location within the cranium or the spine, and there are transition conditions in the cephalic portion of the latter which are not yet fully made out.* § 375. The term paehymeninx (tough envelope) is sometimes used for the dura, irrespective of the recog- nition of a parietal layer of arachnoid. In like manner leptomeninx (tender envelope) is sometimes used for the pia and the commonly admitted visceral layer of arach- noid. TJie pathological terms, pachymeningitis and lep- tomeningitis are derived from these words. § 376. Mg. 795 illustrates: A. The successive cov- erings of the brain, hairy scalp, periosteum, calva * The conditions of investigation of the meninges are peculiar. The pia and arachnoid are relatively delicate ; they are easily torn and their attachments ruptured ; they are surrounded by an unusually tough membrane, the dura, and the whole is enclosed within a case of bone, which must be sawn or otherwise forcibly opened by measures which are almost sure to rupture the pia and arachnoid. It is much to be desired that the subject be reviewed by some anatomist having the use of a mechanical bone-cutting apparatus, e.g., the electro-ostso- tome of the late Dr. M. J. Roberts. 209 Brain. Brain. REFERENCE HANDBOOK OF THE MEDICAL SCIENCES. (calvarium) dura (ental periosteum), arachnoid, and pia. B. The shadowy appearance of a Assure covered by the piarachnoid and the sharper outline when it is re- moved (Fig. 803). C. The difficulty of separating the arachnoid from the pia; in a transection of a Assure, however, the former Fig. 795.— Outline of the Dorso-Lateral Aspect of the Left Half of the Head of an Adult Man, with the Brain Exposed in the Region of the Central Fissure ; 8U. X .3. Preparation.— The entire head was alinjected by continuoua pressure for a week, and medisected as shown in Fig. 670. From the general region of the central Assure was removed a disc of the scalp about 6 cm. in diameter (A) ; in the centre of the area so ex- posed, a cUac of the calva (calyaria, cranial vault) was removed with a trephine 3.5 cm. in diameter, and the corresponding disc of dura cut out (B) . The further preparation of the specimen is described under Fig. 796 ; the present outline is mainly given in order that the region may be located approximately upon the head. will be seen to pass across the Assure from gyre to gyre, ■w?hile the latter, with blood-vessels, dips into the Assure as a fold (Fig. 735). D. The presence on the ental surface of the piarachnoid of a pial fold, the ruga, lying in the Assure. E. The minutely punctate aspect of the depiated cortex Fig 796.— The Several Coverings of the Brain Exposed as a Series of Terraces ; 811. X .9. 1, The arachnoid, the ectal layer of the pi- arachnoid ; 3, a nssure, still covered by the piarachnoid ; 3, ruga, the fold of pia that has been pulled out of the Assure 6 ; 4, ental (pial) surface of the flap of piarachnoid everted from the surface of 5 a gyre, between Assures 2 and 6 ; 6, a Assure from which the ruga and adjacent piarachnoid have been removed. Preparat'kyn.— The region here included is a square of the region shown in Fig 795. The outer line corresponds with the circle A, and the inner with circle B. The scalp was divided obliquely so as to expose a converging surface. A disc of periosteum was cut out a little smaller than the ental Une of the scalp. The original trephined oriflce in the calva was then enlarged with nippers, so as to leave a converging surface, the ectal chcle a Uttle smaller than the hole in the periosteum, and the ental about as much larger than the hole in the dura. Two Assures could be seen ; over the caudal the piarach- noid was left undisturbed ; at the cephalic side of the dural orlAce a semilunar flap was lifted and reflected so as to expose the ental sur- face and the Assure and adjoining gyres which it had covered. by reason of the extraction of minute vessels entermg from the pia. The ental surface, of the pia, here repre- sented smooth, should have a Aocculent appearance, called tomentum, from the attachment of these vessels. § 377. Mg. 797 illustrates : A. The subcylmdncal form of the myel, and the relations of the areas of alba and cinerea at this level; see the article, ^nal Cord. B. The existence of a dural sheath (theca) of the myel, independent of the periosteum, the two being united in the cranium. C. The somewhat loose adhesion of the arachnoid to the dura, leaving slight and scattered subdural spaces. D. The presence of the septum posticum at this level; it is said (Shafer, iii., 188) to be most perfect in the cer- FiG. 797— Transection of the Myel and Its Meninges in the Upper Thoracic Begion. (Enlarged somewhat from Key and Betzius, Taf. i.. Fig. 7, after Shafer : Quain, iil., Fig. 132.) a. Dura (not the spinal periosteum, but representing the ental layer of cranial dura); B, arachnoid : c, septum postlcum ; been recommended by the Association of American Anatomists (December 27th, 1889), by the American Association for the Advance- ment of Science, 1890 and 1892, and by the American Neurological Association, June Sth, 1896. 210 REFEREKCE HANDBOOK OP THE MEDICAL SCIENCES. Brain. Brain. •spine maintain diverse relations, the one with the canal, the other with the myel. I 379. Theea.—The ental or myelic portion of the spinal dura constitutes a fibrous tube, the theca. It is —periosteum — calva —dura Jeetal j ental I — ectal aracbnold — intraraclinoia space I —ental araclinold — subaraclmold space -pia Tig. 798.— Schematic Transection of the Parietal Region of the New Bom, to show the Relations of the Meninges to the Cerehrum and Cranium. (From Langdon, 1891.) 0, C, Cerebrum; F, falx ; S, longitudinal sinus ; xxx, subserous connective tissue between ,Oie dura and the eotal arachnoid. De/ects.*— The mesal dark area dorsad of S (the longitudinal sinus) represents the liea- mentous connection of the two parietal bones ; it should be continuous with the periosteum and ectal dura. The "subserous dura," between the dura and the arachnoid, represented by the series of crosses, is made too wide in proportion. ■considerably longer and larger than the myel itself, and separated from the periosteum constituting the wall of the canal by venous plexuses and much areolar tissue. The cavity between the pia and the dura is occupied by cerebro-spinal fluid (neurolymph), and is divided by the curtain-like arachnoid into the spaces subdural and sub- arachnoid. Within the latter the myel, closely covered by pia, is suspended, being kept in position by a ligament on each side, Ugamentum dentieulatvm, (Fig. 797), which fixes it at frequent intervals to its sheath, and by the Toots of the spinal nerves (Pig. 797, /), which cross the space from the surface of the myel to the intervertebral loramuia. § 380. Mg. 798 illustrates : A. The existence of two layers of dura in the cranium, the one corresponding w^ith the periosteum of the spinal canal, the other with the dural sheath of the myel. Pig. 797, a. B. The existence of two layers of arachnoid — an ental or pial, and an ectal or dural. C. The propriety of regarding the so-called subdui'al space as an intrarachnoid space, analogous with the serous sacs in other parts of the body (see § 399). § 381. Mg. 799 illustrates: A. The formation of a nerve root from the union of several funiculi or rootlets. B. The extension of the myelic dura upon the root at its exit from the spinal canal, to be lost in the sheath of the nerve. § 383. Epidu/ral Bpaee.—la the spine, since there are two layers of dura, an ectal (periosteal) and an ental (myelic), the interval between them constitutes an epi- dural space. In the figures this is nowhere clearly shown, but it may be represented in Pig. 797 by drawing around the present ectal outline, the myelic dura, a second at a little distance therefrom; the interval would be the epi- dural space. § 383. Two questions naturally arise in connection with the epidural space. _. 1. Does it communicate with the subdural space? it «o, where? 2. If not, what is the source of the liquid occupying the space, and what is its nature? _ -^^ j S 384. Fig. 800 ilhistrates : A. The relation of the dura to' the cranium as a complete lining of considerable thickness. *Dr. Langdon informs me that the cut does not represent the ■original drawing quite fairly in some respects. B. The relation of the falx (1) and falcula (13), as mesal extensions of the dura, to the tentorium (8) as a transverse extension. C. The tent-like form of the tentorium, the lateral margins coinciding approximate- ly with the long axis of the cra- nium, the intermediate portion rising toward the meson at an angle rapidly increasing from the occiput cephalad. D. The inversion of the fal- cula as compared with the falx. E. The general arrangement of the more prominent fibres of the falxj there is a marked di- vergence or radiation from about the place of intersection of the free margins of the falx and the tentorium. ' P. The locations of the prin- cipal sinuses along the lines of attachment of the dural folds to one another or to »the cra- nium. G. The direction of the cur- rent in the principal sinuses: in the longitudinal (3) and tentorial (6) (with the falcial) (4) toward the torcular; in the lateral (9), toward the exit in the base of the skull at the jugular vein (4), in the superpetrosal and subpetrosal (10, 11) to the lateral. The entrance of the supercerebral veins into the longi- tudinal sinus at the points indicated by the black spots in the course of the latter and at others not indicated. I 385. Tentorium. — The cerebral region of the cranium is partitioned off from the region containing the cerebel- lum by a fold of the ectal layer of the dura, which, from Fig. 799.— Section, Lengthwise, of a Ventral Nerve Eoot at Its Place of Exit from the Spinal Canal. Enlarged. (From Key and Retzius, Tat. i.. Fig. 10; after Shafer: Qualn, lil.. Fig. 128.) a. Four funic- uli uniting to constitute the root ; 2), dura reflected upon the root at its emergence through the intervertebral foramen (the periosteum is not shown) ; c, arachnoid ; d, reticular lamella of the arachnoid reflected upon the root (compare Fig. 797,/) ; s, subdural space) 8', subara(!bnoid space. its arched shape, is called the tentorium {cerebelU), Pig. 800. See also the article Brain, Circulation of. The tentorium exists in most, if not all, mammals, but not, so far as I am aware, in other vertebrates; in the carhivora it is ossified. § 386. Falx. — Prom the cerebral side of the tentorium extends cephalad a mesal duplicature of the dura, the 211 Brain. Brain. REFERENCE HANDBOOK OP THE MEDICAL SCIENCES. falx, well named from its sickle shape (Figs. 800 and 801) . The narrower cephalic end is attached to the crista gain. The distance between the free margin of the falx Fig. 800.— Mesal Aspect of RigM Half of Medisected Skull Retaining the Dura. X .5. (rrom Sappey, ili.. Fig. 462; after Shafer: Quain, 111., Fig. 129.) Defects.— As usual, there is no indication of the change that occurs at or near the foramen magnum, by which the apparently single dura of the cranium divides Into a true dura related to the myel (Fig. 797) and a spinal periosteum; see, however, Shafer (Quain), ill.. Fig. 182. The region of the postoccipital sinus (12) is so heavily shaded as to give the impression of its considerable width ; as shown in the original of Sappey, this sinus is no longer than the subpetrosal; according to Browning this is merely a constituent of the irregular basilar plexus of venous channels. The vein of Galen (25) here joins the tentorial sinus at an angle of about 4.5° ; really, as shown in Fig. 801, it curves about the rounded splenium and joins at nearly a right angle. 1, Falx ; 2, longitudinal sinus ; 3, concave ventral margin of falx ; 4, falcial (In- ferior longitudinal) sinus ; 5, base of the falx where It joins the tentorium ; 6, ten- torial -(straight) sinus or s. rectus ; 7, cephalic, narrow end of falx, a little dorsad of the crista galU to which it is attached ; ventrad of the line is a frontal (air) sinus, seen also in Fig. 670 ; 8, right side of tentorium, sloping latero-ventrad from the at- tachment to the falx to the side of the cranium along the lateral sinus (9) ; X, the tor- cular, the place of confluence of the two lateral sinuses, the longitudinal and the falcial; 10, the auperpetrous (superior petrosal) sinus: 11, the subpetrous (inferior petrosal) sinus ; 13, postoccipital (posterior occipital) sinus ; the arrows indicate the direction of the blood in the larger sinuses ; the lateral sinus is continuous with the entojugular vein ; 13, talcula (falx cerebelll) ; 14, optic nerve ; 15, oculomotor nerve ; 16, trochlearis nerve ; 17, trigeminus (trifacial) nerve ; 18, abducens nerve ; 19, facial and auditory nerves ; 20, glosso-pharyngeal, vagus, and accessory nerves ; 21, hypoglossal nerve ; 22, 23, first and second cervical nerves ; 24, cephalic end of the W^amentum denticulatum (see Fig. 797) ; 25, union of the velar veins to constitute the vein of Galen opening into the tentorial sinus (see Fig. 801) . and the callosum increases cephalad. The relations of the falx to the longitudinal and falcial sinuses are shown in Figs. 800, 1 ; 801. § 387. Falcula. — This name (wrongly printed /aJcicMto) was proposed by me as a mononym for fcdx cerebelli, designating the mesal fold of dura which extends ventrad from the tentorium to the foramen magnum, where it bifurcates. It is vaguely shown in Figs. 800 and 801. § 388. Fontanels (Pr. fontanelles). — These are the in- tervals between the corners of the infantile parietal bones before these corners have formed sutural union with the adjacent bones. There are six fontanels, two mesal and two pairs of lateral. The lateral, at the cephalic and caudal angles of the ventral border of the parietal bone, are small, irregular, and of comparatively little interest. The two mesal fontanels are at the ends of the sagittal suture; their more common designations, ante/nor and posterior, may appropriately give place to prefontanel and postfontanel. % 389. Analogy of the Fontanels with the TOos.^The structure of a tela was described in § 33. But since, in mammals at least, the telas are always more or less closely adherent to adjacent parts, and their margins are easily detached, their relations are sometimes not clearly ap- preciated. But if an infant or fetal cranium be divided across the prefontanel diagonally so as to include either parietal bone and the opposite frontal, the cut edge will pre- sent three layers, viz., an ental, the dura, representing the endyma; an ectal, the pericranium, representing the pia; an intermediate, the bone, representing the nervous parietes. At the fontanel this third element is absent, and the conjplned dura and pericranium contribute a mem- branous area quite comparable with a tela and available for illustration thereof. A defect in the analogy is this : The cranial bone is of nearly uniform thick- ness, and thins out at the margin of the fontanel. But in the brain, although the immediate margins of the telas may be thin, the general parietes are com- monly very massive, and there is usually a parallel zone specially differentiated, e.g., the habena.* § 390. Fig. 801 illmtrates (in addi- tion to the points mentioned under Fig. 687 and in § 66): A. The degree of re- tention of the dura in this specimen is greater than with any brain ever seen or heard of by me. The brain was most skilfully removed, according to my direc- tions, by Prof. W. C. Krauss, a former- student (see the article Brain : Methods). B. The existence, in the caudal three- fifths of the cerebrum, of a distinct and considerable mesal depression, contain- ing the longitudinal sinus, so that here the retreating surface of the dura is seen beyond its dorsal cut margin ; pre- sumably this corresponded with a mesal thickening of the cranium. C. The distinctly sickle-shape of the mesal extension of the dura between the two hemicerebrums, whence its name/ato. D. The non-correspondence of the width of the falx with the area dorsad and cephalad of the larger part of the callosum. E. The location, form, and extent of the medicistema {cisterna a/mhieni), the irregular space between the cerebellum, the splenium, and the geminums, roofed by the arachnoid and tentorium. P. The location, form, and extent of the ventricisterna {cisterna intercruralis), between the crura, the pons, and the tuber (f-uher cine- reum), infundibulum and hypophysis. It forms a very deep indentation of the ventral outline of the brain, cor- responding with the cranial or mesencephalic flexure (Fig. 671). It is bridged by the arachnoid, following substantially the line of the dura, and thus includes the arteries of this region. G. The location, extent, and form of the postcisterna (cisterna magna cerebello-medullaris), the interval between the dorsum of the oblongata, the cerebellum, and the ad- jacent portion of the cranium, or strictly the ectal layer of arachnoid in that region, represented by the black line marked 10 (see Pigs. 806 and 807, § 408). H. The location of the metapore (foramen of Magen- die), the orifice in the metatela {tela choroidea inferior), constituting the roof of the metacele or meten cephalic portion of the " fourth ventricle " (see §§ 78-83). In this * It is proper to add that, although this analogy between the telas and the fontanels had already occurred to me, I was reimpressed with it on listening to an admirable lecture upon the anatomy of the brain by Prof. D. K. Shute, at the Columbian Medical College, Washington^ D. C, December 16, 1889. 212 REFERENCE HANDBOOK OF THE MEDICAL SCIENCES. Brain. Brain. termatic a. pseudooele' rostrum 1 : genu I ; specimen its relations are complicated by tlie postcere- bellar artery, a loop of which lies just dorsad of it (see under Defects). I. The location of the postcerebellar artery. This is not named on the figure and is imperfectly shown. The central portion, from its origin at the vertebral, is invisi- ble here, but shows in Figs. 691 and 806. Just at the side of the metapore it turns sharply upon itself, forming a loop, somewhat as in Fig. 806; but in the present figure the peripheral portion of the artery alone is seen, and looks as' if it began in the metapore. The two principal divisions are as here represented. There is apparently considerable variation in the course and subdivision of this vessel. J. The length of the longitudinal sinus, equalling nearly the greater curvature of the cerebrum ; its cephalic end was probably not quite reached. K. The presence of the lalcial sinus (3) along the ventral, free margin of the falx. This is said to be often wanting. I suggest that the alleged absence of this sinus in the fetus sometimes may be due to its non-detection. L. The straight course of the tentorial sinus in line vfith. the falcial, along the ventral margin of the caudal fifth of the falx, where the latter is continuous with the tentorium (Fig. 800, 8). The tentorial sinus is not named or otherwise designated on this figure, but in Fig. 800 it it is numbered 6; it is also called straight sinus or sinus rectus. M. The junction of the mesal longitudinal and ten- torial sinuses at the torcular (Herophili). The course of the lateral sinuses thence is indicated in Fig. 800. N. The location of the right velar vein (3) between the splenium of the callosum and the conarium, and its junction with its opposite at the point indicated by .the circular spot at the edge of the splenium, just in line with the dotted line from that word. The two velar veins form the short vein of ■Galen. O. The brief course of the vein of Galen about the splenium, and its entrance at 4 into the tentorial sinus, at the place of continuity of the latter with the falcial when this is present. P. The location of the right precerebral artery (anterior cerebral). Branches of this are seen dorsad and cephalad of the callosum. The main trunk extends dorso-cephalad from the chiasma. The dark spot between the dotted lines leading from the words ter- ma and precommissure repre- sents the junction of the two precerebral arteries at the meson; in some cases they are separated by a consider- able interval and communicate by a slender precom- municant artery. Here, however, they unite by their full width and again diverge. Q. The origm of the termatic artery from the place of jimction of the two precerebrals ; its course, parallel with the terma and copula, then around the genu at least to the dorsum ; its short branches to the terma and adjoin- ing parts of the hemicerebral meson. R. The location of the postcerebral artery. The be- ginning of this, severed from the basilar, is represented by the circular spot between the hypophysis and the convexity of the pons. Prom it are seen small arteries entering the crura. For the two large vessels repre- sented in the ventricisterna, see under Defects. § 391. Pia.— This was formerly more often called pia mater, sometimes also meninx vasculosa (Ger., "' porta fomlcommlssure medicoiimiissure velum aulix babena supracommissure aula precommissure optic n. oblasma I hypophysis ' albicans torcular postcrlbrum myel | myelocele \ nodulus \ '10 metatela metapore FIG. 801.— Mesal Aspect of the Bight Half of the Brain of an Adult White Man ; 378. X .65. 1, AuU- plexus; 2, falcial sinus; 3, right velar vein; i, orifice of Galen's vein into the tentorial sinus; 5, falcula or " cerebellar falx " ; 6, tentorial sinus ; 7, uvula, a mesal division of the cerebellum ; 8, tuber ("tuber clnereum") ; the line seems to stop at the artery, but should reach the thin floor of the dlacele .lust caudad of the hypophysis ; 9, ventral end of the falx ; 10, cut edge of the ectal layer of the arachnoid, § 408 ; the line is too heavy and should be white instead of black ; at a point be- tween the lines from 6 and 7 it becomes attached to the cerebellar plarachnoid ; 11, longitudinal sinus. Preparation.— The brain was removed in the dura. It was duly supported and injected through the basilar artery with the starch mixture containing alcohol described in the article Methods, etc. The injection caused the brain to fill the dura completely, and presumably assume its natural form. It was then hardened In alcohol and medisected. The same specimen was the basis for two figures in my paper, 1885, 6, and this figure is reproduced in the work of C. K. Mills, 1897 ; the mesal cav- ities are shown on a larger scale in Fig. 687. ne/ects.— Although one of the purposes of the preparation of this figure was to Indicate the relations of the dura to the brain, the word dura is omitted altogether. Falx designates its mesal extension between the halves of the cerebrum, as shown in Figs. 800 and 804. Along the longi- tudinal sinus (11) should be indicated the points of entrance of the supercerebral veins (see Fig. 800). The sinus, dorso-caudad of the cerebellum, between the torcular and the point marked 4, should be named tentorial stnvs. On the precerebral artery, dorso-cephalad of the chiasma, are two orifices. The more caudal, at the root of the termatic artery, is caused by the removal of the left precerebral (see § 390, P). The more cephalic, between the lines from copula and aula, should be omitted, together with the intervening depressed area ; they represent an accidental excavation of the artery. The arteries in the ventricisterna, the interval between the pons, the crura, and the tuber are vaguely and inaccurately shown (see 8 390, F) . The postcerebellar artery (undesignated but lying between the lines from metapore and metatela) looks as if it begins in the metapore (see, however, § 390, H). The pia is nowhere distinctly represented. The black line marked 10 is the ectal layer of the arachnoid (see Fig. 806) ; the ental layer, in contact with the cerebellum, may be recognized ; they unite Just dorsad of the line from 7. The curved white line about midway be- tween the callosum and the fomlcommissure is due to an error ; the surface of the hemlseptum forming the lateral wall of the pseudocele should be uniformly shaded. For other defects see Fig. 687. 213 REFERENCE HANDBOOK OF THE MEDICAL SCIENCES. Hirnhaut, weiche Eimhaut ; Fr., pie-mh-e). It is deli- cate, fibrous, highly vascular, and intimately connected with the neuron (central nervous system), into the sub- stance of which it sends numerous nu- trient small vessels. "When stripped off, these vessels commonly break at a short distance from the pia, and their number and minuteness impart to the ental surface of the membrane a floc- culent or woolly aspect, the fomentum (§ 376, E). § 392. Myelie Pia.— This is thicker and firmer than the encephalic, less vas- cular, and more closely adherent to the nervous substance. It has sometimes been called the "neurilemma of the cord. " Two layers are recognized : the ental,' sometimes called intima pia, sends a fold into the ventral ("anteri- or ") fissure, and into the dorsal a la- mina not recognizable as a fold. Along the ventri-meson the pia presents a con- spicuous fibrous band, the linea splen- dens, not represented in Fig. 797. § 393. Enceplialic Pia. — According to Shafer (Quain, iii., 186), only the ental of the two myelic layers of the pia is represented on the brain, but where and how the other layer dis- appears is not stated. The pia fol- lows all the undulations of the ence- phalic surfaces, dipping into the fissures and rimulas as folds or rugas of cor- responding depth (see Fig. 796). At the bottom of the intercerebral fissure, the mesal cleft between the dorsal por- tions of the two hemicerebrums, the pia enters the callosal fissure at either side, is then reflected, and crosses the cal- losum * § 394. Telas and Plexuses. — For these structures of the pia see §§ 33-34. § 895. Fig. 803 illustrates: A. The differelnt aspect of the cerebral surtace (a) before the removal of the piarach- noid or leptomeninges, as in the ceph- alic (upper) third of the figure; (J) after it has been removed completely, as in most of the caudal two-thirds; and (c) when there remains the in- parietal ■paracentral Fig. 802.-Central Region of an Adult Brain, Partly Denuded of Pl- araelinoid and Exhibiting on the Bight a Departure from the More Common Relation of the Postcentral and Paracentral Fissures; 4,232. X .5. 1, The caudal end of a fissure which is mostly covered by the pia ; 2, a small spur of the postcentral representing the usual caudal branch, which is marked 5 on the left ; 3, an undetermined Assure ; 4, a triangular depression comparable, perhaps, with the expansion of 5 on the left ; 6, the cephalic branch of the left post- central. traflssural fold, as in the left central and the part of the right central crossed by the line. * Since the pia is practically the ectal surface of the brain, its cut edge is not commonly represented excepting when the flgure is on a very large scale ; but on blackboard diagrams its vascular character may be instructively indicated by a red line. On such diagrams the endyma (" ependyma " or lining of the cavities) may be represented by yellow or green. B. The usual relation of the central fissures to the paracentrals on both sides. C. The usual relation of the left paracentral fls- intercerebral flssure olfactory Assure olfactory bulb olfactory tract Sylvian fissure optic nerve entocarotid artery hypophysis oculomotor nerve crural eistema basilar artery trifacial nerve tentorial interval vertebral artery" postoblongata spinal artery myel postcistema Fig. 803. -Base of the Brain of a Man Estimated at Sixty-Five Tears, Before the Removal of the Plarachnoid and Blood-Vessels ; 4,206. X .5. 1, Between the meson and the right- olfactory bulb and opposite the point where the arachnoid ceases to pass directly from one hemicerebrum to the other and is carried into the intercerebral fissure by the f alx (compare Figs. 801 and 804) ; 2, cut or torn margin of the arachnoid at the crural eis- tema ; 3, an artery on the right lateral lobe (pileum) of the cerebellum, cbl.; 5, 5, indi- cate approximately the lateral boundaries of the postcistema (Fig. 80T); O., occipital lobe of the cerebrum ; T., temporal lobe ; f ., frontal lobe. sure to the dorsal fork of the postcentral (compare Fig. 769). D. The less common condition of the dorsal end of the right postcentral, the caudal branch being short and th& cephalic so long as to intrude between the central and the paracentral and render that portion of the postcentral gyre quite narrow (§ 11, D ; compare Fig. 664). § 396. T?ie Arachnoid. — The word a/raAnoid is derived from the Greek apaxvv (signifying either a spider or a. spider's web), and elSoc (form or likeness).* In general, the arachnoid may be described as a nonvascular mem- brane, enveloping the brain and closely attached to the pia, excepting where the latter dips into the intervals be- tween the masses or into the fissures and sulci of the cere- brum and cerebellum. These depressions are bridged, so to speak, by the arachnoid, excepting where the dural folds, falx and falcula, carry it for a certain distance into the intercerebral fissure and the interval between the cerebnim and cerebellum. Wherever the arachnoid re- mains the outlines of parts are more or less vague, as in Figs. 796, 803, and 803. § 397. Mg. 803 illustrates : A. The general aspect of the base of the brain when first removed from the cranium ; the outlines are less distinct than after the removal of the- piarachnoid (compare Figs. 673 and 689), and certain * The open-meshed discs of the common garden spiders, Bpei/ra., Argiape, etc., are not comparable ; rather the compact glazed sheet- constructed by one of the house spiders (Tegenaria) which will hold- water, or the still more substantial nest of the water spider OLrgyro- netra) , which is like a stationary diving-bell and retains the air place* under it against considerable pressure. 214 REFEREKCE HANDBOOK OF THE MEDICAL SCIENCES. Brala. Brain. features are wholly invisible, e.g., the chiasma, precrib- rum, and crura. B. The varying relations of the arachnoid to the inter- vals between the masses. For nearly half of the distance between the optic nerves and the cephalic end of the cere- brum the arachnoid crosses directly from one frontal lobe to the other so that the intercerebral fissure is barely recognizable as a slight mesal depression. But at the point indicated by 1 the fold of dura constituting the falx (Figs. 801 and 804) begins and forces the arachnoid into the depths of the fissure. The arachnoid dips slightly into the Sylvian fissure, and deeply into the interval be- tween the cerebrum and the cerebellum on account of the dural fold, tentorium (Fig. 800, 8). 0. The existence of a considerable interval, the crural ("peduncular") cisterna just caudad of the hypophysis, between the crura and adjacent brain surfaces and the arachnoid ; the latter was torn and cut in removing the brain, and the sharp artificial margin is indicated by 3. D. The existence of the postcisterna (" cisterna magna " or " cerebello-medullaris ") between the oblongata and the cerebellum ; by blowing dorsad at either side of the ob- longata, where the arachnoid is torn, air entered the post- cisterna and it expanded so as to have a convex outline as in Fig 807 ; but when the photograph was taken most of the air had escaped and the extent of the cisterna is in- dicated only by the greater vagueness of the cerebellar outline as far as 5 at either side. § 398. As to details, however, our knowledge of the arachnoid is even less complete and satisfactory than that of the dura and pia, and there are direct contradictions in the accounts by different anatomists which I have as yet been unable to reconcile. As stated by Langdon (1891), Bichat described (1803, 1813) the arachnoid as a serous, shut sack, conforming in all essential particulars with the serosa of the other cavities. But most recent writers follow K81- liker (1860) in denying the existence of a parietal lay- er in contact with the dura, and Tuke regards (1883) even the visceral layer as merely an element of the pia. § 399. On February 17th, 1888, I made and re- corded the following ob- servation upon a child, still-born, at term. No. 3,358: In removing the parietal dura, a delicate membrane separated from it more or less easily in dififerent localities on the two sides; it was observed also by my colleague. Prof. S. H. Gage.* § 400. On December 39th, 1890, Dr. Langdon's paper (1891) was presented before the Association of American Anatomists. He records observations made upon two children, at term, and one adult. His summary is as follows: "The arachnoid is a true shut sac, similar in structure and function to the serosa of the other great cav- ities. Its parietal layer is easily separable from the dura at the vertex in the fetus and young infant, but practically * Although this distinctly indicated the existence of a parietal (ec- tal) layer ol arachnoid, at that time I supposed the subject, Menmges, would be treated by another, and was, moreover, then luUy occupied with the articles already- undertaken ; hence the observation was not made public and the point has not been followed up. inseparable in this region in the adult. At the base of the skull it is demonstrable as a separate membrane, even in the adult. To assert that the parietal layer of arachnoid is absent because its subepithelial connective tissue has fused at the vertex with the dura (connective tissue), is as incorrect as to describe the great omentum as one layer of peritoneum, because its original four layers have be- come matted and adherent." § 401. During the preparation of the article Meninges in the first edition of the Rbfbkencb Handbook I verified the correctness of the previous observation as to the pres- ence of an ectal or dural layer of arachnoid, and noted its reflection upon the carotid and vertebral arteries to be- come continuous, presumably, with the ental, pial, or vis- ceral layer. But no such reflection occurs at the nerve roots unless at some depth within the foramens of exit, and this point I have as yet not had time to determine. § 403. Mg. 804 illustrates: A. The relative positions of the meninges (compare Figs. 796 and 798). B. The formation of the longitudinal sinus within the substance of the dura. C. The projection of the arachnoid villi into the sinus and the parasinual spaces; see the article Pacchionian Bodies. D. The accumulation of the vjUi at one point, on the right, to such an extent as to cause the protrusion of the dura, and presumably a depression of the ental surface of the cranium. E. The separability of the arachnoid from the pia, leav- ing a distinct subarachnoid space increased along the fissure lines. F. The contemiinousness of the arachnoid and the falx, and their separation by a distinct interval. § 403. Mg. 806 illttstrates : A. The complete circum- ■meduUa Fig, 804. — Transection of the Dorsal, Mesal Region of the Cerebrum, to Show the Meninges and Arach- noidal VUU. SUghtly enlarged. (From Key and Ketzius, Taf. xxlx.. Fig. 4'; after Shafer : Quain, iii.. Fig. 134.) PrexMM-abion.— The spinal subarachnoid space (Fig. 797, ft, I) was injected with a fine blue mass, which Med (and distended ?) the corresponding space upon the cerebrum and entered the arachnoid villi. The original figure is appropriately colored and on a larger scale. Judging from the relation be- tween the width of the falx and the interval between it and (he callosum, the plane of section was not far oephalad of the splenium (see Fig. 801). c.c, Callosum ; /, falx ; s, longitudinal sinus ; s.a. (at the left), subarachnoid space. Defeats.— The pia is not so distinct as I would make it. The relation of the arachnoid to the ven- tral margin of the falx is not quite clear. There is no extension of the cortical oinerea upon the dor- sum of the callosum as an indusium (see § 217). There is no indication of the existence of the two layers of the dura, e.g., periosteal and encephalic, described by Langdon (Fig. 798) . The f alcial (inferior longitudinal) sinus may have been absent in this case, as it is said to be in many. The lacunw lateraUs are somewhat indistinct, probably in consequence of the reduction from the original figure, where they are much more clearly shown. scription of the true encephalic cavities, excepting at the metapore. B. The non-communication of these cavities with the pseudocele (fifth ventricle). C. The presence of considei'able, in'egular intervals, subarachnoid spaces, or cisternas, between the pia and the arachnoid. D. The continuity of the largest of these, postcisterna, 215 Brain. Brain. REFERENCE HANDBOOK OF THE MEDICAL SCIENCES. between the cerebellum, postoblongata, and occipital part of ttie cranium, with the spinal subarachnoid space. E. The relation of the falcula (falx cerebelli) to the riG. 805.— Medisectlon ol the Cerebellum and Adjacent Parts. (From Key and Retzlus, 1875, Taf . ¥iil., Til., Fig. 1 ; after Sbater : Qualn, 111., Fig. 131, reduced and somewhat modl- ned.) Compare Figs. 670, 800, and 801. 1, 1', Atlas vertebra ; 2, 2', axis vertebra ; 3, diacele (third ventricle) ; i, epicele, the cephalic or cerebellar portion ol the " fourth ventricle " ; C, cerebellum ; C.C., callosum ; C, callosal gyrus ; M, post oblongata ; P.V., pons ; X, falcula (falx cerebelli) ; c, medicommissure ; c.c, just dorsad of (behind) the myelocele (central canal of the cord) ; /.M., metapore ("for- amen of Magendie ") ; p, hypophysis ; t, torcular. Preparation. — A blue mass was inject- ed into the spinal subarachnoid space ; the head was then frozen and medisected. The original includes the mesal aspect of the entire head, less the Integument and mandible. The true encephalic cavities and the subarachnoid spaces are colored, so only the actual mesal parts appear. Defects.— In the original there is no in- dication of the arachnoid, although the circumscription of the subarachnoid space was the very feature supposed to be illus- trated. Should it be claimed that the arachnoid is sufficiently indicated by the ental boundary hue of the dura, the an- swer would be that, although in places the two meninges may be in contact, they are not in all; furthermore, as distinctly shown upon Taf. vi. of the same worlj, in Figs. 801, 806, and 807, there is a point near the crest of the cerebellum (nearly opposite t) where the arachnoid (or its octal layer) leaves the cerebellum and passes directly to the dura at (be foramen moQnum: There is no boundary between the metepicele (fourth ventricle) and the subarachnoid space ; even if , as in other cases, the membranous roof of the meta^ cele (metatela) adheres to the caudo-ven- tral surface of the cerebellum, the plexuses and the endyma constituting its ental surface must end somewhere. Since the cavities are not colored, they appear as white areas without perspec- tive, as if the preparation were a thin mesal slice. Most unfortunately, probably through some defect in execution, there is left a clear line between the epiphysis and the splenlum, as if there were a pass- age from the diacele (third ventricle) to the irregular subarachnoid space between the splenlum, epiphysis, pregeminum, and cerebellum. This is altogether misleading, for, as shown in Figs. 670, 687, 759, and 801, and stated in g 66, H, the dia- cele is completely circumscribed at that point by the endyma reflect- ed from the velum upon the epiphysis. In the present copy this de- fect has been remedied so far as it could be by uniting the epiphysis and splenlum so as at least to block the passage ; but It should be remembered that it is closed not by nervous tissue but mem- branes. The editors of Quain have represented the missing nietar tela by the dotted line from near the number 4 to near the abbrevlar tlon /.M. A continuous Une would have been more appropriate, and separated farther from the metacellan floor; that could not be changed in the present copy, but the interval representing the meta^ pore (foramen of Magendie) has been enlarged; this, however, is conventional, and as if to correspond with the perhaps unusual con- dition shown in Fig. 690. Finally, the falcula (falx cerebelli), which was unmarked in Qualn, is here designated by across (x). mesal portion, vermis, of the cerebellum. In Fig. 707 this is obscured by the fact that part of the left lateral lobe remains. § 404. The Cisternas.—M. several regions the ental layer of arachnoid is separated from the pia by consider- able spaces, called cisternas by Key and Retzius, 1875, p. 93.* They are enumerated and described by Browning. § 405. Mg. 806 illustrates ; A. The general appearance of this aspect of the cerebellum together with the oblon- gata and pons ; in Fig. 697 these two parts were omitted. B. The extent of the postcisterna (aisterna magna or c. eerebello-medulla/)-is) upon about one-half the entire caudal aspect; there is, however, considerable variation in this respect. C. The definite dorsal and lateral limitation of the postcisterna, although the boundary line is undulating and asymmetrical. D. The lack of ventral boundary of the cisterna; the ectal layer of the arachnoid is attached to the dura so that this cisterna is continuous with the spinal subarach- noid space. E. The union of the two vertebral arteries to form the basilar. F. The origin of the postcerebellar arteries from the vertebrals near their junction. vallis postvennis postcerebellar a. vertebral a. FIG. 806.— Caudal (Lower) Aspect of the Cerebellum, etc.; 376. X .9. „ , ^ . ^ » Prewcwation.- Through the kindness and skill of Dr. W. C. Krauss (a former student, now professor in the Medical Department of Niagara University, the bram was receivaJ fresh and in the dura. The cavities were injected with alcohol ; the arteries first with al- cohol and then with the starch mixture (see article Brain: Metftods). The alcohol passed through the metapore into the postcisterna and thoroughly preserved all the parietes ; it had access also about the myel, where the arachnoid was cut in removing the bram. The ectal layer of the arachnoid was cut away along the line of its attachment. Defects.— The perspective of the postoblongata is defective. The metapore is vaguely indicated and few ol the vessels are shown. Of the lobes only the tonsiUas are outUned. The flocouli and nerve roots are omitted, also the rimulas (Interfoliar crevices) on the left side. The most serious detect is the non-indication of the dorsal Umlt of the endyma which presumably accompanies the metaplexuses ; see § 417. 1, 3, Branches of the postcerebellar artery, the former passing between the cerebellum and the oblongata, the latter apparently supplying the corresponding metaplexus ; 2, 6, edge of the ectal layer of arachnoid bounding the area whence it had been cut away ; 4, loop of postcerebellar artery, an example of its tortuous course ; 5, main trunk of the artery near where it reaches the crest of the cerebellum ; its branches are omitted ; 7, mesal ridge formed by the vein which divides into a right and left branch upon the caudal surface ; the arachnoid here forms a somewhat sharp angle. G. The length and course of the postcerebellar artery, and the tortuous course of its central portion. * Admitting that most of the cisternas do lie between the arachnoid and the pia, as commonly described, my later observations lead me to regard the postcisterna as between two layers of the ental arachnoid Itself (see Figs. 805 and 807). 216 REFERENCE HANDBOOK OP THE MEDICAL SCIENCES. Brain, Brain. H. The passage of a branch of the postcerebellar artery mesad toward the metapore, apparently supplying the metaplexus. plarachnold dura postverrais prevermis [nold dura and its arach- Intraraclinold space ectal layer of ental araclinoid postcisteraa [araclinoid ental layer of ental pia paravermian sulcus Dostvermis pial fold Tig. 807.— Sections of the Cerebellum and Postcisterna ; semldiagram- matic. A. Dorsal (cut) surface of the ventral portion of the cerebellum, together' with the adjacent dura and the large " subarachnoid space," postcisterna, commonly called cistema magna or c. cere- heUo-medullarig. At the meson appears the postvermis, separated by the pararermlan sulci (1) from the large lateral lobes ; 3 is the «ntal layer of the arachnoid. The meninges are here represented by lines only. B. Enlargement of the meso-caudal region of A. The meninges are here represented by zones conventionally shaded ; 2, the place of Junction of the two layers of the ental arachnoid at the margin of the postcisterna. Preparation.— An adult cerebellum (2,891) was divided at a plane •corresponding with the line X— Y In Fig. 806, so as to separate the dorsal two-flf ths ; on Fig. 801 the plane of section would be indi- cated approximately by a line across the unshaded (out) surface connecting the points where the dotted lines from the words nodM- lus and epieele intersect the margin of that surface ; as seen in Fig. 806 It passes dorsad of the plexuses. The ectal layer of arachnoid is represented as the continuous caudal boundary of the postcisterna, while in Fig. 806 it is supposed to have been trimmed closely along the line of its depression from the ental layer 3. Defects.— VoT readier comparison with Fig. 806 the figures should lave been inverted so as to have the postcisterna nearer the reader. In B the postcisterna is enlarged two diameters, but the several zones representing the meninges are disproportionately widened, and their shading is conventional for discrimination only, and not for the Indication of histological structure. The ectal or dural layer of arachnoid was Inadvertently omitted, and there is no indication of the two layers of the dura Itself. The numerous rimulas and In- tervening follums that were divided In the section are not Indicated, and the usual relations of the pia and arachnoid to each other and to narrow encephahc depressions generally are illustrated only at the paravermian sulci. According to the ;present view * that the metapore is the orifice of an evagination, the postcisterna may be lined. In part at least, by endyma ; but it was not recognized in this preparation, and even in the embryo represented by Blaise (1898, Fig. 26) it seems to have disappeared at a lower level. I. The extension of the metaplexuses dorsad from the metapore upon the cerebellum. § 406. Postcisterna. — Notwithstanding the presumption that all the cisternas form a continuous series, my obser- vations, up to the present time, induce me to regard the * At the time § 83 was made up into the page I was unaware that the German edition (1894) of Minot's " Embryology " has this passage, p. 698 : " The foramen of Magendle (Wilder's metapore) and the open- ings of the lateral recesses, according to this view, would be not true perforations of the ependyma, but the outlets of evaginatlons." space in the angle between the cerebellum and the ob- longata as presenting an important peculiarity, viz., as lying, not between the pia and the visceral arachnoid, but between two layers of the latter. The facts upon which this view is based cannot be detailed here. The view is indicated upon Pig. 807. I am aware of the difficulties involved in its acceptance ; without question, the postcisterna communicates on the one hand with the true encephalic cavities through the metapore, and on the other with the spinal subarachnoid space ; its free communication with the other cisternas, although commonly accepted, seems to me not yet clearly demonstrated. § 407. la tliere Direct Communication of the Suba/raeh- noid Spaces with tlie Intra/rachnoid {or Subdural) Space ? — Whatever view they adopt regarding the constitution of the arachnoid as a whole, most writers agree that the arachnoid covering .the brain and myel is continuous, ex- cepting for the capillary spaces about the nerve roots re- ferred to in § 401. Hence, while the neurolymph may pass to and fro between the true encephalic cavities and the postcisterna through the metapore, and may thus enter the other cisternas (§ 406) and the spinal subarach- noid space, it is nevertheless confined thereto. But Dr. Langdon (1891) holds that "at the base of the cranium there are two points where the visceral [ental] arachnoid is deficient, one on either side, in the ' bridge ' of arachnoid which stretches across from the cerebellar lobes to the under [ventral] surface on the oblongata. These foramina measure about half an inch (13 mm.) in longitudinal diameter by one-fourth inch (6 mm.) trans- versely, and are crossed by three or four fibrous bands, the attachment of which to the edges of the openings produces a multiple crescentic appearance of their mar- gins, which suggests the name ' lunulate foramina.' " It will be noted that the location of these alleged lunu- late foramina in the arachnoid corresponds with that of the ventral ends of the lateral recesses. Hence, on the one hand, if both are natural, the transfer of the neuro- lymph from the true encephalic cavities to the arachnoid space is provided for; on the other, the relation of the nerve roots to both the pia and the arachnoid renders both liable to rupture during extraction or manipulation of the brain. , Hess implies (1885, Pig. 10, or.) that the arach- noid was cut and reflected at this point. On the whole subject, and on the metapore see the later observations of Blake, 1900. § 408. Mg. 807 illustrates : A. The usual relation of the meninges in these respects, viz., the independence of the dura ; the adhesion of the pia to the brain substance ; the dipping of the pia into the narrow depression at either side of the vermis as a vascular fold ; the adhesion of the arachnoid to the pia over most of the cerebellum, so as to constitute a piarachnoid (Pig. 796). B. On the caudal aspect of the cerebellum, the forma- tion of a considerable space, the postcisterna, by the separation of an ectal layer of the ental or visceral layer of the arachnoid. § 409. The inadequacy of the foregoing account of the postcisterna and its relations with the metapore is fully conceded. It is no disparagement to the labors of Blake and others to add that no account known to me is alto- gether clear, consistent, correct, and complete. The dif- ficulties involved can be fully appreciated only by those who have already attempted to elucidate the subject. The material must be specially prepared for the purpose and examined by improved methods, both anatomical and histological. Burt Gt. Wilder. § 410. The following list includes treatises upon the gross anatomy of the brain, mostly recent, likewise a few special papers ; other papers are named in the text. Other things being equal, preference is given to such as contain full bibliographies. The history of Neurology up to 1833 is given in Burdach. For current literature consult the Journal of Gomparatiw Neurology ; Anato- mischer Anzeiger ; Index Medieus ; Neurologisches Central- blatt; Brain; L' Encephale ; Nevrdxe; Jahresberiehte 217 Bralu. Brain, REFERENCE HANDBOOK OF THE IHEDICAL SCIENCES. fiir Anatomie, etc. See § 13. A. A. A. Proc. stands for Proceedings of the Association of Amei-ican Anatomists. Bibliography. Blake, J. A., 1900: The Eool and Lateral Eecesses ol the Fourth Ventricle Considered Morphologically and Embryologically. Read before the Assn. Amer. Anat., December 28th, 1898. Jour. Comp. Neurol., X., 79-108, 7 plates. Broca, P., 1888 : M^moires sur le cerveau de I'homme et des pri- mates, 0. Burckhardt, K., 1895 : Der Bauplan des Wlrbelthiergehims. Morpho- loglsche Arheiteu, Iv., 131-150, tat. vill., 1895. Bnrdach, K. F., 1822: Vom Baue and Leben des Gehims, Q., 3 vols. Clark, T. E., 1896 : Comparative Anatomy of the Insula. Joum. of Comp. Neurol., vi., 59-100, 5 plates. Dalton, J. C, 1885 : Topographical Anatomy of the Brain, Q., 3 vols. Dana, C. L., 1893 : Text-Book of Nervous Diseases ; Being a Compen- dium for the Use of Students and Practitioners of Medicine, 0., niustiated. New York. Dejerine, J., 1895 : Anatomie des centres nerveux, R. O., 2 vols.. Vol. !.» pp. xill. and 816, 401 figures. [The macroscopic anatomy occu- pies pp. 233-517 of vol. 1.] Eberstaller, 0., 1890: Das Stimhim; einBeitrag zur Anatomie der OberflSche des Grosshims, O., pp. 140, with 9 figures and 1 plate ; Wlen. Edlnger, L., 1896: Vorlesungen tther den Bau dernervosen Central- organe des Menschen und der Thiere. Fifth edition, R. O., pp. 386, 258 figures, Leipslc. (See also HaJl, translator, 1899.) Edinger, L. u. Wallenberg, A., 1899: Bericht iiher die Lelstungen auf dem Gebiete der Anatomie des central Nervensystems. (566 titles, 1897, 1898, with commentaries.) Schmidt's Jahrbiieher der Ge- sammte Medicin, cclxii., pp. 72. Findlay, J. W., 1899 : The Choroid Plexuses of the Lateral Ventricles of the Brain, their Histology, Normal and Pathological (in relation especially to Insanity) . Brain, vol. xxii., 1899, pp. 161-202 ; 3 plates. Fish, P. A., 1890 : The Epithelium of the Brain Cavities. Amer. Soc. Micros. Proc, 140-1«, 1 plate, 1890. , 1893 : The Indusium of the Callosum. Joum. Comp. Neurol- ogy, iil., 61-68, 1 plate. , 1899 : The Brain of the Fur Seal, Callorhinus urstnus, with a! comparative description of those of Zalophus Califomlanus, Phoca vitulina, Ursus Amerioanus, and Monachus troplcalls, 0., pp. 20, 4 plates. From the report on the Fur Seals and Fur-Seal Islands of the North Pacific Ocean, part lii. Flatau u. Jacobsohn, 1899 : Handbuch der A natomie u. Vergleichenden Anatomie des Centralnervensystems der Saugetiere, I., Makro- skopischer Tell, R. 0., pp. 578, 6 plates, 120 figures in text, Berlin. [Contains a good bibliography.] Gage, Mrs. S. P., 1895 : Comparative Morphology of the Brain of the Soft-Shelled Turtle (Amyda mutica) and the English Sparrow (Passer domestica). Proc. Amer. Micros. Soc, xvil., 185-228, 5 plates. , 1896 : Modifications of the Brain During Growth. Abstract of paper read before the Amer. Assn. Adv. Sci., August 24, 1898. Amer. Naturalist, xxx., 836-837, October, 1896. Gerrish, F. H. (editor and collaborator with Bevan, A. D., Keiller, W., McMurrioh, J. P., Stewart, G. D., and VFoolsey, G.), 1899 : A Texl^ Book of Anatomy by American Authors, E. 0., pp. 917, 950 figures, Philadelphia and New York. Glacomini, C, 1884 : Guida alio Studio delle Circonvoluzioni Cerebrali, 0., Turin. Gordinier, H. C.» 1899 : The Gross and Minute Anatomy of the Central Nervous System, R. O., pp. 589, 48 plates and 213 figures, Philadelphia. Gould, G. M., 1900 : Suggestions to Medical Vi^riters, 0., pp. 180, Phila- delphia. Hall, W. S., 1899 (translator of Edinger, "Vorlesungen," 1896): The Anatomy of the Nervous System of Man and of Vertebrates in Gen- eral, R. O., pp. xl. and 446 ; 258 figures, Philadelphia. HervS, G., 1888 : La Crrconvolution de Broca, 0., pp. 275, Paris. HUl, Alex., 1890 (translator and annotator of Obersteiner's " Anlei- tung" (1887) : TheAnatomyof the Central Nervous Organsln Health and in Disease, O., pp. 432, with 198 illustrations, Philadelphia, 1890. Hill, Charles, 1900 : Developmental History of Primary Segments of the Vertebrate Head. Contribution from the Zool. Laboratory of the Northwestern Univ. ZoOlogischer Jahrbiieher, Abt. f. Anat.'u. On- togenie der Thiere, xlil., pp. 393-446, 3 plates and 4 figures in text. [Preliminary paper in Anat. Anzeioer, 1899, 353-369]. His, W., 1895 : Die anatomische Nomenclatur. Nomina anatomlca, Verzeichniss der von der Anatomischen Gesellschaf t auf ihrer IX. Versammlung in Basel angenommeneu Namen. Eingeleitet und im Binverstandnlss mlt dem Redactionsausschuss erlaiitert von Wllhelm His. Archiv fur Anatomie und Physiologie, Anat. Abth., Supplement Rand, 1895, O., pp. 180, 27 figures, 2 plates. Ibdnez, G., 1899: Die Nomenclatur der Himwlndungen. luaug. Dissertation, Berlin, pp. 37. Key u. Eetzius, 1875 : Studlen in der Anatomie des Nervensystems, F., 2 vols., Stockholm. Krause, W. [editor], 1880: Handbuch der Menschlichen Anatomie, 3 vols., O. Hanover. [A later edition, 1899, is in course of publica- tion.] Langdon, F. W., 1891 : The Arachnoid of the Brain (read before the Association of American Anatomists, December 29th, 18n. .■■■■■. >:f ■ MS^iismtiii>. Arthrotome. Tracer. Fine Curved Forceps. Fig. 985.— Some of the Instruments Uselul In the Removal or Dissection of the Brain. All of actual size. (From "Anatomical Technology.") The two upper are eye-knives ; the syringotome is commonly called canaliculus knife ; it is of great use for exploring oriflce.s, the porta ("foramen of Monro") and the metapore ("foramen of Magendie"), and for dealing with membranes and plexuses where a point or a prominent edge might do injury ; it has been my favorite instrument since 1886. The tracer may be employed sometimes in place of the more costly syringotome, but its chief use is In isolating nerves and vessels by tearing the connective tissue. Most forceps are too stiff and soon tire the hand or hinder delicacy of manipulation ; the coarse " Coxeter " forceps represented have the blades excavated so as to be Ifehter than usual. The flexible blowpipe is most readily made by attaching to a piece of rubber tubing, 30 to 40 cm. long, the smaller half of the metal blowpipe commonly sold with dissecting instruments. The length of the tube enables the object inflated to be held at a con- venient distance from the eye ; since inflation is temporary Injection, the advantages of witnessing the effects are obvious. A larger volume of air may be utilized by using the larger half of the metal pipe, and glass cannulas of any size may be employed. The arthrotome has the handle continuous with the blade, and one edge of the blade is rounded, excepting near the tip ; It is practically a cartilage kntte. The fine curved forceps represented have the points simply serrated ; but for the removal of the pia from the brain surfaces, and especially from the depths of Assures, a pair with interlocking teeth, like those of artery forceps, will be found very useful. 384 REFERENCE HANDBOOK OF THE MEDICAL SCIENCES. Brain. Brain. Stage, such as I have framed for the brains of the cat (W. and G.) and sheep ("Physiology Practicums "). § 137. Instru- ments. — The instru- ments employed in the removal or dis- section of the brain (§§ 50, 136) should, as a rule, be re- served for that pur- pose. If used in ordinary dissection their points and edges should be at- tended to without delay. Some of the less familiar instru- ments are shown in Fig. 985. §. 138. Probe- Pointed Curved Bis- toury. — This is practically a longer and stronger syr- ingotome (Fig. 985), the cutting edge being about 5 cm. (3 in.) long, ending in a probe point. The curve is less than that of the syringotome. It replaces the latter in the dissection of the entire human brain, and it is par- ticularly applicable to transecting the brain through the mesencephal, to tracing the medi- cornu, and to slit- ting the arachnoid in following the Sylvian or other deep fissures. § 139. Besides the instruments shown in Figs. 985 to 987, the following, more familiair, are indispensable: Scalpels of three sizes: large for sections; niedium for ordinary dissection ; small ('"^ CharriSre ") for finer dissec- tion. Scissors, curved flatwise, three sizes. A hand lens, tripod magnifier or " linen tester. " A bone- chisel, or ordinary chisel of moderate width, or even a screw-driver sharpened slightly. A syringe, metal, or rubber bulb. Absorbent cotton ; if com- mon cotton is used it must be first thoroughly wet in alcohol or water. Cannulas, rubber tubing, and the Y -tubes or T-tubes for branching of injection tubes may be had of dealers. The smaller end of a straight " medicine dropper " makes a fair cannula. Fig. 986.— Diagonal Side-Cutting Nippers. A. little less than actual size. From " Anatomical Teclinology." This is the smallest size of the English make (Stubs'), and for most purposes should hare the handles lengthened by pieces braced on. The German and Swiss in- struments (for sale by large hardware dealers) are less highly finished and costly, but answer nearly as well. Of these, seven sizes are made, ranging in length from 10-20 cm. (4-8 inches), and in price from 60e. to $1.50. Surgical bone forceps and dental wedge-cutters have a spring between the handles and are more expensive. The nippers are most serviceable for removing the calva of infants and fetuses and of small animals. In use they must cut or squarely break the bone; the pulUng and tearing to which one naturally re- sorts will inevitably tear the brain or its meninges. the ordinary carpenter's instrument; it should be kept sharp and well-set, and used for no other purpose. For dividing the cranium any small saw will answer, but the edge should be rather fride so as to make a broad kerf. For medisection of the head, however, the saw should be very large, fine toothed, thin (i.e., make a narrow kerf), have a removable back, and be very sharp and free from rust. § 141. Saw-Box. — This (which might be called a macro- tome) is a coverless box made of boards about 2.5 cm. (1 in.) thick, and with the following inside dimensions: length, 30 cm. (13 in.); height, at middle; 35 cm. (10 in.) sloping to 15 cm. (6 in.) at the ends; width, ac- cording to the length of the neck attached to the head, 35-40 cm. All the parts must be accurately squared and put together with screws. The sides should go outside the bottom and ends, and the bottom have a cleat at each end. Each side is to be divided squarely at the middle of its length by a saw of the same thick- ness as that with which the head is to be cut; the bot- tom also is to be sawn to the depth of 1-3 mm. When finished the box should be thoroughly oiled, inside and out, with linseed or olive oil, to prevent warping when it is wet. § 143. Bead-Best for the Bemoval of the Brain. — The following description and figures (988, 989, and 983) are from the paper of B. B. Stroud (1900, b) who devoted much time to the device. The apparatus was shown at the meeting of the Association of American Anatomists in Washington, May 3d, 1900. " This apparatus was devised for the purpose of hold- ing the head firmly with the base of the cranium hori- zontal. This enables the base of the skull to serve as a shallow tray in which the brain is supported during its removal. The subject lies upon the belly, being sup- ported by adjustable clamps fitting into the auditory meatuses, and the head naturally assumes a position in which the long axis of the cerebrum is nearly horizontal. Repeated trials in the neurological laboratory at Cornell University this spring have shown that with a maxi- mum of convenience to the operator there is a minimum of danger of rupturing the cranial nerves and certain delicate structures of the brain itself, which are fre- quently torn when the usual methods are employed. Pig. 988 shows a general view of the apparatus. Fig. 989 shows details of construction. In Fig. 983 it is rep- resented in use. " The device consists of a baseboard A to which is at- tached at right angles a second board B. Both are of seven-eighths-inch oak. , Professor Wilder suggested that the upright board should be hinged to the base for con- FIG. 987.— Steel-Handled Spatula. X 0.5. (From catalogue of Whitall, Tatum & Co.) This (or a palette-knife, or round- ended shoe-knife, ground thin so as to be flexible) is indis- pensable for detaching the dura when the calva is to be removed. The methods of making and securing cannulas, and of making injections, are detailed in "Ana- tomical Technology," pp. 137-148. Cheap and efficient pinch-cocks may be had in the form of the wooden, spring clothes-pin, which may be variously attached to the wire cranes or used in- dependently upon the tubes. § 140. Sams. — There is no special advantage of the expensive surgical or anatomical saw over Vol. II.— 85 Fib. 988.— Head-Best for the Removal of the Brain. Devised by B. B. Stroud. A, Baseboard; B, upright board, hinged to A and secured by hooks. (From Stroud's paper, 1900, b ; see Figs. 983 and 989.) ! 385 Brain. Brain. REFERENCE HANDBOOK OF THE MEDICAL SCIENCES. venience in storage and transportation. This is a very- valuable improvement. "The upright S— Figs. 988 and 989, A— has a middle emargination and the sides are cut at an angle as shown in Fig. 989, A. The chin-rest D is hollowed upon the top to lit the chin. It slides in a shallow groove 0.5 cm. (i in.) deep, cut in B, and is adjustable by means of the thumbscrew. The two lateral bars E are of iron. They project 3.5 cm. (1^ in.) above the board B, and serve to support the two jaws i''and O. " The two clamps for grasping the head, Fig. 983, shown in detail in Fig. 989, B, consist of the jaw F, the guides AA Fig. 989.— Portions of ttie Head-Rest. A, the upright board, with Its side Irons, JE. B, One of the two clamps for grasping the head. C, Improved form of the jaw-piece, F. I, and the screw J, which pierces F in the form of a spike n, 3 cm. (f in.) long, to enter the auditory meatus. A flat head J, Pig. 989, B, is more convenient for turning the screw than the roimd milled head shown in Pig. 988. The jaw ^ is bent flatwise to fit the curve of the skull and grasp it dorsad of (posterior to) the mastoid process. The other end is curved downward, to fit under the zygoma and thus hold the head more firmly. The guides J are made from one piece of steel bent in the form of a rectangle and made to fit very closely to the top of the side iron E. They and the curved form of i'' prevent a disagreeable rocking motion of the head. F is firmly riveted to I by means of four double-headed rivets. The upright B is held in position by the two hooks K andi."* * For the convenience of those who may desire to construct the head- rest the detailed speciflcations are here reproduced : A and B are made of %-in. oak. ^ is 30x40 cm. (12x18 In.). B Is 30x26 cm. (12xlOJ4m.). It Is cut as Indicated in Fig. 989, A. The middle cut isl5xl3cm. (6x5in.). The front side contains a groove J^ in. deep and 85^ In. wide to receive the chin support D. X) is of oak 5 x 9 x 17 cm. (2 X 354 x 6^ in.) . The top is hollowed out to fit the chin 4.5 cm. One and seven-eighths in. from the top it is cut down so as to be only .5 in. thick. There Is a slot In the middle to accommodate a set screw for fastening It at the different heights. E Is an iron bar, 17x2x1 cm. (% X M X % in.), and is bent at a point 3.5 cm (1^4 in.) from the top so as to be perpendicular to the base A. F is of A in. steel, 9x3 cm. (3M X IJi in.) and formed as shown in Fig. 989, B and C : 1 is the front end shaped so as to fit under the zygoma ; 3 Is the rear end and grasps the temporo-occipital bone dorsad of the mastoid process. The clamps I are made of %-in. steel 12 x 2.5 cm. (4?4 x 1 in.) and bent as shown in Fig. 989, B. The screw J operates the ]aw P. It Is made of ^in. iron 4 in. long. It has a shoulder which is received between F and /. The spike H projects one inch beyond P to be inserted into the auditory meatus. A flat head is more convenient than the round one shown in Hg. 988. All sharp edges should be rounded and smoothed to avoid accidental injury to the operator's hands. § 143. Agate-Ware Pans. — The brain anatomist will find most convenient, and in the end most economical, onie or two " nests '! of iron pans, " enamelled, " so as not to rust, with plates of the same for covers. For the largest size (11 X 4 in.) covers of glass or metal must be provided; this size will accommo- date a half head. § 144. Butter jars, 10 X 10 cm., or 10 X 30 cm., with tin screw-cap, parchment lined, are sold by the Excelsior Package Co., 49 Warren Street, New York. They are very convenient for temporary storage or for transportation. § 145. Labelling Speci- mens. — Much of the real value of a specimen de- pends upon its identifi- cation as being a certain part of a certain brain, taken from an individ- ual of a certain age, sex, and nationality, and pre- served in a certain way. Even if the possessor has so few specimens that he feels sure of re- membering the entire his- tory of each, his death would abolish the source of information. I have observed surprising in- stances of carelessness in this regard, even upon the part of some who should set an example of scientific accuracy. Were the specimen never to be removed from the jar in which it alone is kept, the object could be accomplished by inserting the label in the jar or attaching it Fig. 990.— Specimen Jar, with Glass Top, Rubber Ring, and Clamp. (Made by Whltall, TatumA Co., New York.) Fourteen sizes are made, ranging from three to nine Inches in diameter, and of various lengths. The size here shown is 6 X 12, and will receive a half brain or the two halves of a medisected cerebrum; for undivided brains and for medi- sected heads the size 9X8 sufBces. These two sizes cost, respectively, 810 and $18 a dozen. The prices given in the catalogue are subject to a discount of fifty per cent. thereto; but this is rarely an adequate precaution^ neither is it often possible to state all the desirable data upon a label attached to the specimen itself. The most satisfactory plan tried is the adoption of a serial number for each brain. § 146. All Specimens are Nirni- iered. — As soon as received every brain is assigned a number which permanently designates it and all parts into which it may at any time be divided ; the same number per- tains to all notes, photographs, and drawings of it. § 147. Sometimes, as with entire brains or half -brains, it is possible to attach with a cord a metal (sheet block tin, stamped) number. But commonly the numbers are written with India ink* upon bits of parch- ment and attached by small (rib- bon) pins, t § 148. For purposes of dissection, photographing, or drawing it may sometimes be necessary to remove the label, but ordinarily it should be affixed to some other re- gion, so that there may be no possibility of misplacement. * Good pencil marks last a long time in alcohol, but ordinary black ink is speedily washed out. + In time ordinary pins corrode and may break the brain subsrance when withdrawn ; pins of aluminum or ^ver should be available at a moderate cost. Fig. 991. — Landen- berger's Specimen Jars. These have a rubber ring and a glass top retained by a wire. The smaller size is 3 X 3 In., capac- ity 6 oz. (180 cc); the larger, 3X4 (hteh), capacity 10 oz. (300 cc). 25 N. Thirteenth Street, Philadelphia. 386 EEFERENCE HANDBOOK OF THE MEDICAL SCIENCES. Brain. Brain. § 149. Distinctive Labels.— The ready recognition of cerebrums belonging to groups may be provided for as follows: A. The sexes are distinguished by using quadrangular labels for males and circular ones for females. B. Presumed normal white brains have white labels ; Africans (of all shades), gray ; murderers and other crim- inals, red; insane and idiots, blue. § 150. Immediate JRecords are Made. — No one's memory is conceded to be infallible. All data concerning a brain not obtainable from the ■ specimen itself are recorded without delay under the number assigned to it; e.g., the sex, age, known, believed or estimated, race, known or supposed weight when fresh, donor, mode of initial pres- ervation, weight or bodily condition of the individual, and his character or mental state. § 151. Card Catalogue. — The basis of the records of each brain is a card bearing the number of the specimen at an upper corner. Upon the face of the card are written the data men- tioned in § 150; also, or continued pon the back, the numbers of neg- tives, and references to published figures or descriptions ; suggestions IF 'lllimil 1 1 f points to be elucidated are com- .il I lllflHUIIf, 1 lonly put on paper slips.* § 152. Drawing is insisted upon, f These drawings should be, primarily t least, in outline only; shading, like charity, " covereth a multitude Fig. 992.— TaU, Eound, of sins." Screw - Capped Jar, b 153. In begmnmg the study of withNlckel-Plated g, difficult region, the student is ad- Caps, Cork-Lined. . j j. j ^ • j. TlSee sizes, viz.: four vised to determine at once some prominent feature as a landmark, as a "base," so to speak, "of intel- lectual supplies," from which he may explore in any direction, and to which he may return when doubts arise. § 154. No observation involving either complex manipulation or novel results is published until it has been submitted to at least one other trained observer. § 155. It is freely admitted that rarely, if ever, is all possible information gained from a specimen at one ex- amination or by a single observer ; hence specimens are preserved, t § 156. Methods of Bepresenting the Brain. — The follow- ing considerations and suggestions apply more or less directly to all natural history illustrations, but with especial force to the human brain, on account of its soft- ness when fresh, the difficulty of preserving it, the great size of the entire organ, the minuteness of certain por- tions, the large number of recognizable parts within a * My own use of slips of convenient size for notes and drawings and descriptions began in 1867 wtiile I was assistant in comparative anato- my at tbe (Agassiz) Museum of Comparative Zoology at Cambridge, Mass. The slips were about three by Ave inches. When the first United States postal card was issued that size (13.5 X 7.6 cm., 5.25 X 3 in.) was adopted. But tbe subsequent introduction of other sizes has invalidated that standard, and the common and increasing em- ployment of the catalogue card of the Library Bureau (7.5 X 135 cm. or 3 X 5 in.) may render it desirable to adopt that size for notes as well. Brief accounts of the " sUp system of notes " are given in Sci^rwe, January 16th, 1885. and in Wilder and Gage. + Every student of any branch of natural history should compel him- self to learn to draw, however slight may be his inherited artistic ca- pacity. Not merely the laboratory students in Cornell University, but the members of the large general classes in physiology and zoology are required to make drawings of entire animals, and of the parts ex- posed in their dissections. t The time has not yet come, and indeed shows no signs of ap- proach, when I can look at even a familiar brain preparation without learning a new fact, gaining a better insight into what was already known, or receiving an impulse toward some special inquiry. A good example of the desfrability of preserving specimens for later scrutiny Is furnished In my last paper, 1900, a (see p. 196). ounces, eight ounces, and sixteen ounces. (Whitall, Tatum & Co., New York.) Answers well for diry or non- volatile contents or for the temporary storage of alcoholic speci- mens. small area, the continuity of all, the contiguity of some which are otherwise associated but remotely, the inter- mixture of two differently colored substances, the com- plicated relations of the meninges to each other, to the vessels, and to the cavities, and the preponderance of curved and oblique contours over straight lines and planes. § 157. Importance of Orientation. — With all organs, but especially with the brain, it is essential that the lo- cation of the region represented be easily recognized; otherwise details may be unappreciated or even misap- prehended. So far as possible, therefore, less familiar parts should be accompanied by such as are unmistak- able. It might seem that useless expense was incurred by the publishers of Bourgery and Jacob's magnificent plates in the introduction of faces artistically drawn and colored ; but even the expert neurologist is guided in the comprehension of the relative position of brain parts by reference to the apparently superfluous facial outlines. § 158. Enlargement of Complex Begions. — It often hap- pens that the same section or dissection includes regions that are comparatively simple, and others that are very complex ; shown upon a single scale, either the complex parts are unintelligible, or the total is undesirably and needlessly large. Hence, just as the histologist aims first to obtain a general view of all the parts in their gross relations, and then focuses a higher power upon a selected region, so the delineator of encephalic structures should give first a view of the whole, if only an outline, and then an enlargement of complex parts to any extent re- quired for tneir complete elucidation; he can hardly make this enlargement excessive. Compare, e.g., Quain's figures, 258 and 290, and Pigs. 669, 670, 671, and 695 in this volume. § 159. Terminal and limiting parts, membranes, and apparently atelic (functionless) parts and conditions should be distinctly shown, or the insufficiency of their representation admitted. "The little things of the brain " might well form the subject of an entire article. Prom the standpoints of physiology and medical practice such parts as the terma, valvula, crista, epiphysis, hy- pophysis, and habena, and such conditions as the reflec- tion of the endyma upon the plexuses, and the dorsal limitation of the porta, are of comparatively slight im- portance. But their morphological significance is, at least in some cases, inversely to their functional activity, and they cannot be ignored without endangering the success of any attempt to understand or explain the structure of the brain. g 160. Anatomical figures should be something more than pictures conveying a general and vague idea. Where is there an adequate representation of the relation of the diatela to the habena, and of the cephalic end of the latter? Prom the published figures could any stu- dent be expected to comprehend the locations and bound- aries of the " foramina of Monro " or of " Magendie " ? The tenia is easily enough shown as a white band throughout most of its course, but where are its extremi- ties accurately delineated? Any one can see the caudate prolongation of the striatum, but representations of its termination at the tip of the medicornu are as rare as are figures of the extremity of the fllum terminale. Even so considerable a part as the flocculus is seldom figured in such a way as to display either its form or its attach- ment. § 161. The avoidance of the morphological incongrui- ties and deficiencies which are to be detected in nearly every portrayal of encephalic anatomy demands the ad- mission of three propositions, which are mere truisms in themselves, but radical affirmations when contrasted with their almost universal non-recognition in anatomical works : 1. Every part, organ, membrane,* or surface is either * So essential is the exemplification of celian circumscription and endymal continuity that the endyma should be represented by a dis- tinct and rather heavy line, continuous excepting at the metapore ; see p. 152, Fig. 687. 387 Brain. Brain. REFEKENCE HANDBOOK OF THE MEDICAL SCIENCES. limited or continuous with some other part. If limited, its limits must be defined ; if not, its extension must be indicated. 3. Every cavity is either open or closed. If closed, the continuity of its parietes must be demonstrated ; if open, its communications must be shown. 3. Every elongated part has a middle and two extrem- ities ; not only the former, but the latter must be repre- sented. § 162. Figures — original ones especially — should be multiplied and descriptions reduced. In descriptive an- atomy, whether human or comparative, the text should be subordinate to the illustrations. Some treatises (Charles Bell, Meckel, Milne-Edwards, etc.) seem to have been prepared upon the idea that the description is essential and the figures merely supplementary ; on the contrary, words should be employed only when pictures will not suffice — that is, for explanation, commentary, generaliza- tion, hypothesis, and manipulative directions. The arguments for the multiplication of figures may be summarized as follows : 1. A figure is usually a guaranty that something like the object represented has been seen, at least by the artist, and that a certain amount of time has been devoted to its contemplation. 2. The information conveyed by a figure is more real, and likely to be more lasting, than that which is expressed in words. In respect to reality and impressiveness, the sources of knowledge may be ranked as follows, in an ascending scale : (1) Description ; (3) picture ; (3) model ; (4) object seen; (5) object handled; (6) object personally prepared. The picture is thus intermediate in value be- tween the thing itself and a description of it. 8. A figure, if clear and properly placed, is more read- ily understood than a description, and a saving of time is thus effected. It may be easier for the author to write than to draw, or even than lo supervise a drawing, but his personal inconvenience or loss of time should not out- weigh the gain to his readers. This applies particularly to dictionaries, cyclopedias, and journals, which are commonly read or consulted in haste. Editors and pub- lishers would find eventual profit in offering to authors the fullest encouragement to employ illustrations so far as possible and curtail their descriptions in proportion. That it is rather the exception than the rule for such en- couragement to be offered is probably due to several causes: (a) Publishing houses have usually a staff of printers who must be employed, whereas the various processes involved in the making of pictures are com- monly done outside at extra expense ; (b) authors too often content themselves with carelessly made copies of " stock figures " instead of insisting upon original representations of objects prepared by themselves. Hence, on the one hand, the exceptionally liberal publisher is liable to get a poor return for any allowance made for drawings, and, on the other, the exceptionally painstaking author is apt to be told that, at best, the engraving will be done if he will furnish the drawings; and, if he cannot draw him- self, their cost is likely to deter him from their introduc- tion. In short, all the existing conditions work to the disadvantage of the reader, who gets but a " pennyworth of f pictorial] bread to a monstrous deal of [verbal] sack." Before this state of things can be amended the authors of books and papers must see clearly the importance of il- lustration ; to paraphrase an epigram as to the making of an index, the drawings should be made or personally superintended by the author, even if some one else has to write the text. 4. Figures usually occupy less space than descriptions conveying an equal amount of information. This means condensation, convenience, and economy in the present, and a due consideration for our successors in the not far distant future. Exact data are not accessible, but no thoughtful and public-spirited person (unless he be a publisher or printer) can contemplate without concern the logical results of the present rate of book-making activity. § 163. Borrowed figures should be fully credited, and all modifications, whether of size or features, explicitly stated. To copy is to compliment, but unacknowledged copying is theft, and unspecified change is misrepresen- tation. The ill effects of omitting to state the source of a figui-e are two : (1) The originator loses credit to which he is justly entitled; (2) the reader may be seriously misled by the apparent duplication of some really unique feature or the confirmation of an error. For example, in the representations of the meson of the cat's brain by Leuret (Leuret et Gratiolet, PI. V., Fig. 3), the paeudocele (" fifth ventricle ") is made even more extensive than in man, reaching almost to'the splenium. The figure is re- produced, without credit or correction, in Mivart's " The Cat" (Fig. 139). Whoever remarks the coincidence in respect to the pseudocele, but fails to note that one figure is simply a copy of the other, may naturally infer that the feature in question is normal, or at least not anomalous. On the other hand, if informed that three of Mivart's figures (135, 136, 139) were copied from Leuret, the stu- dent might conclude that the representation of the base of the brain (Fig. 138) was derived from the same source. This would be most injurious to the reputation of Leuret, for the figure in question displays several features (the size and direction of the hypophysis, the disconnected fissure on the temporal lobe, the relations of the pons to the trifacial and abducens nerves) which it is safe to say never were observed in a feline brain. Nor is it enough to give the sources of figures in a list, or in the preface, as in Huxley's " Vertebrated Animals " ; so great is the labor of preparing an original figure that the acknowledgment of it should be equally as explicit as that of a verbal quotation. Finally, in the case of modified figures, it needs but a moment's reflection to see that nothing short of an accu- rate statement of the nature and extent of the alteration can insure full justice to the originator. § 164. Drawings should be made as notes. In many cases an outline * drawing, even if hastily made, would convey to the maker, or any one else, at a future time more prompt and complete information than could be embodied in writing covering the same space. But the general employment of sketches, in addition to words, or in place of them, can hardly be looked for until chil- dren are taught to draw the intelligible objects about them before they are drilled in the making of the — to them — unmeaning pot-hooks of the alphabet. § 165. Figures should be more frequently employed in preliminary or incomplete publication. lYobably one of the reasons for the comparative inf requency of pictorial representations of normal, abnormal, and pathological structures, especially in journals, is the difficulty, often the impossibility, of preparing a detailed figure in time for pubUcation. But this need not prevent the early ap- pearance of a figure,-if only in outline, illustrating one or more points of greatest importance. § 166. Figures should be based upon photographs. Photography enables the anatomist to (a) record the ap- pearances of perishable specimens, or of such as are in course of dissection ; (6) insure the proper perspective ; (c) save time and labor upon the part of the draughtsman, and thus either reduce the cost of the drawings or render a larger number attainable. It is seldom that a single anatomical preparation is so perfect as to display all that is needed, and yet present no superfiuous parts ; often, too, certain points are to be brought out with " diagrammatic clearness, " others being subordinated or omitted altogether. Hencei as a rule, the photograph forms rather the basis for the completed figure, and two or more similar preparations may be re- quired for the elucidation of all the desired features, f * There is a general and almost unconquerable predilection for shaded drawings. However advantageous shading may be in ordinary art as an element of finished pictures, and when merely a general effect is desired, in anatomical figures correct outlines are essential, and shading should be deferred until the last. . t A chief obstacle to the employment of photographs as a basis for figures of brains and embryos has been the difficulty of supporting such delicate objects within range of the camera in its usual horizon- 388 REFERENCE HANDBOOK OF THE MEDICAL SCIENCES. Brain. Brajn. i 167. Figures should be placed so as to be most readily understood and instructively compared. In comparing pictures of two or more houses, ships, or stoves, the architect, ship-builder, or dealer places them in such positions with regard to one another and 'his own eyes as may minimize the effort at mental transposition. If asked the principle on which he acts, he will probably say that no principle is needed, that he simply follows nature, experience and common sense. With few exceptions it seems to be reserved for those whose business is the contemplation of natural objects, who are credited with more than the average degree of intelligence, and who have at command the recorded experience of centuries, to disregard a mat- ter whose simplicity is equalled only by its importance. In most works there is an utter absence of system. Seldom, indeed, are symmetrical figures placed other- wise than with the meson coinciding with that of the observer, but even this would be less likely to confuse than the apposition of transections of a subcylindri- cal mass like the myel with the dorsum above in one case and below in another.* The prevalent careless in this regard may be as- scribed to three sources : [a) The still too common idea that illustrations are of secondary importance ; (d) the fact that most figures have been copied and thus placed without regularity, as in the original : (c) some time and trouble are required to reverse them. § 168. General Rules for the Placing of Figures. — These rules are based upon a consideration of the whole subject. There is probably no one of them to which exceptions may not exist ; but such exceptions should always have a well-defined reason and not occur through inadvertence. 1. Figures should be coadjusted so as to facilitate comparison with one another and with typical struct- ures in normal positions. 2. The dorsal side should be uppermost. 3. Direct views are to be preferred to oblique, though the latter are at times indispensable ; e.g.. Figs. 726, 769 and 775. 4. Symmetrical figures, or parts thereof, should be so placed that the meson is vertical, e.g. , Figs. 664, 672, and 682. 5. When there is no choice between the right and left sides, the latter should be represented. 6. Of medisected organs, unless there is special reason for choice, the mesal aspect of the right half is to be shown, t ? 169. Designation of Parts upon Figures. — The full technical names of parts should be given if possi- ble. From the purely artistic point of view, of course, any extraneous line upon a picture is a disfigurement. But if it be once admitted that the primary object of an anatomical drawing is to convey accurate informa- tion, then, unless the shaded figure can be duplicated in an outline (as in Tiedemann, Vicq d'Azyr, and Dal- ton), there should be no sacrifice of the essentiat to the accessory. It may be a question whether the names should be upon the parts (as in Gray), or at the sides of the fig- ure and connected with the pprts by lines (Gegenbaur). Upon the whole the latter method seems preferable, especially if the technical names are used. tal, or nearly horizontal, position. This obstacle is wholly re- moved by the photographic table devised by Professor Gage and used by us in Cornell University since 1873. With this the camera may be readily adjusted to an^^ angle, and brought into a vertical position so as to cover an object lying upon cotton, or in alcohol, or even alive in water. The apparatus is described and figured in Science, April nth, 1884. * The common disregard of uniformity in this respect was made the subject of a communication by a medical professor to the Association of American Anatomists at its meeting in De- cember, 1892. t If the fuller discussion of this subject in the New York Med- ical Journal, August 2d 1884, be consulted, the following cor- rections should be made : Explanation of Fig' 57, last line, transpose antimesal a.a& sym- mesal. Fig. 59 for antimesal read symmesal. Fig. 64, for symmesal re,a.& antimesal. \ 170. Abbreviations should represent technical terms ; they should be uniform throughout the work, and be placed at the sides of the figure. Four methods of designating parts by abbreviations have been employed : i, By numbers and non-signifi- cant and unuuiform letters, which may or may not be explained in the text (Owen) ; 2, by non-signifi- cant characters, uniform only in part, and explained at a distance from the figure (Reichert) ; 3, by uni- form and significant, but partly vernacular abbrevia- tions (Parker) ; 4, bv uniform technical abbreviations (W. andG.) The advantages of uniformity in the use of abbrevi- ations are obvious, but it is by no means easy to avoid the charge of ambiguity. Where uniformity is not attempted, care should at least be taken to avoid the same abbreviation for the names of parts which are liable to be taked for one another. For example, in Schwalbe's two representations of the lateral aspect of the crura and adjacent parts (Figs. 280, 281) not only are opposite sides shown for no good reason, with some differences of detail which are puzzling rather than instructive ; not only is the pons designated in one by /> and in the other by/o, and the tractus opti- cus by to'va. one and tr.o in the other ; but the letters tp stand for the tcsnia pontis in Fig. 280, and in Fig. 281 for the tractus peduncularis transversus [cimbia]. Since these parts are similar in general appearance and direction, and only one appears in each figure, it is doubtful whether any but the most expert anato- mist, thoroughly familiar with this somewhat obscure region, could escape at least a temporary misapprehen- sion. \ 171. Abbreviations should be explained in alpha- betical order. The "practical" business man would exclaim, "Of course, how else should they be?" An "unscientific" child would adopt the alphabetical or- der with letters as he would the order of notation with numbers. But the super-scientific writer, especially if he be a German, scruples not to save a few mo- ments of his own time at the expense of others, by giving the verbal equivalents of ten (Huxley, Fig. 19), fifteen (Balfour, ii.. Fig. 271), twenty (Quain, Fig. 263), twenty-five (Schwalbe, Fig. 279), forty (Mey- nert [Strieker], Fig. 253), or even fifty-eight (March- and. Arch. f. mik. Anat. xxxvii., 331, 332) abbrevia- tions, either in no recognizable order at all or as they occur upon the figure.* The time wasted by each consulter of the figure (not to mention the effect of just indignation) would nearly equal what it would have cost the author to place the abbreviations in alphabetical sequence. Burt G. Wilder. Bibliography. Donaldson, H. H , 1894 : Preliminary Observations on Some Changes Caused in Nerve Tissue by the Reagents Commonly Employed to Harden Them. Joum. of Morphology, 1894, pp. 122-126. Fish, P. Ai, 1893 : Brain Preservation, with a R6sum6 of Some Old and New Methods. The Wilder Quarter-Centuiy Book, pp. 385-402. 1 plate. , 1894 : Abstract of the foregoing. Journ. Nerv. and Men- tal Disease, February, 1894, pp. 101-103, plate. , 1895, a : Formalin for the Preservation of Brains. Pre- liminary Note. Journ. Comp. Neurology, v., 125-128, JCly, 1895. , 1895, b : The Use of Formalin in Neurology. Proc. Amer. Micros. Society, xvii., 319-330. . 1897 : The Mummification of Small Anatomical and Zoo- logical Specimens. Proc. Ass'n Amer, Anat., December, 1897, pp. 59-61. Stroud, B. B., 1897 : On Brain Preservation. Proc. Ass'n Amer. Anat., 1897. pp. 30-32. , 1900 : a New Head-Rest for the Removal of the Human Brain. Proc. Ass'n Amer. Anat., May, 1900, pp. 10-14, five fig- ures. Wilder and Gage, 1892 : Anatomical Technology as Applied to the Domestic Cat, third edition, from the second revised, O., pp 6cx), 130 figures, and 4 lithographic plates. Wilder, B. G,, 1896,2-: The Desirability and the Feasibility of the Acquisition of Some Real and Accurate Knowledge of the Brain by Precolle^ate Scholars. Amer. Soc. Naturalists, De- cember, 1896. Science, vi., 902-908, Dec. 17th, 1897, 3 figures. *Even more objectionable is the omission of the original pagination upon the reprints of papers. The printer does not always realize the conditions and the author often remembers when it is too late. 389 ^ ^ii.>^. _-;^^ V. '^ ^, ri ^^ ^J^-i-\^ J ^H. 'N^v^ v^*^ \ -* .ai^ 4^^ 'V te*"^ rr^' > ^ _ ^-'^^k^ ^^h'p^ A