Digitized by the Internet Archive in 2016 https://archive.org/details/anatomicalmemoir21good ANATOMICAL MEMOIRS OF THE LATE JOHN GrOODSIR THE ANATOMICAL MEMOIRS OF JOHN GOODSIR F. R. S. LATE PROFESSOR OF ANATOMY IN THE UNIVERSITY OF EDINBURGH EDITED BY WILLIAM TURNER, M.B. PROFESSOR OF ANATOM V IN THE UNIVERSITY OF EDINBURGH WITH A BIOGRAPHICAL MEMOIR BY HENRY LONSDALE, M.D. FORMERLY LECTURER ON ANATOMY VOL. II. EDINBURGH ADAM AND CHARLES BLACK 1868 (j oOc i Si'' V> X Printed by R. Clark, Edinburgh. CONTENTS OF YOL. II. DIVISION I. I. On the Origin and Development of the Pulps and Sacs of the Human Teeth (Edinburgh Medical and Surgical Journal, Jan. 1839.) II. On the Follicular Stage of Dentition in the Ruminants, with some Remarks on that Pro- cess in the other Orders of Mammalia (Transactions of British Association for Advancement of Science, August 1839.) III. On the Mode in which Musket - Bullets and other Foreign Bodies become inclosed in the Ivory of the Tusks of the Elephant . (Transactions of Royal Society of Edinburgh, January 18, 1841.) IV. On the Supra - Renal, Thymus, and Thyroid Bodies ...... (Philosophical Transactions, January 22, 1846.) V. On the Morphological Relations of the Ner- vous System in the Annulose and Vertebrate Types of Organisation .... (Edinburgh Philosophical Journal, January 1857.) VI. On the Morphological Constitution of the Skeleton of the Vertebrate Head . (Edinburgh Philosophical Journal, January 1S57.) VII. On the Morphological Constitution of Limbs . (Edinburgh Philosophical Journal, January 1857.) Page 1 53 5G 66 78 88 198 VI CONTENTS. DIVISION II. VIII. On the Employment op Mathematical Modes of Investigation in the Determination of Organic Forms ..... (Daily Mail, July and August 1849.) IX. On the Horizontal Curvature of the Internal Femoral Condyle ; on the Movements and Relations of the Patella, Semilunar Carti- lages, and Synovial Pads of the Human Knee-Joint ...... (Edinburgh Medical Journal, July 1855.) X. On the Mechanism of the Knee-Joint . (Abstract in Proceedings of Royal Society, Edinburgh, January 18, 1858.) XI. On the Curvatures and Movem-ents of the Acting Facets of Articular Surfaces XII. Lecture on the Retina .... (Edinburgh Medical Journal, October 1855.) XIII. On the Mode in which Light acts on the Ulti- mate Nervous Structures of the Eye, and on the Relations between Simple and Com- pound Eyes ..... (Proceedings of Royal Society, Edinburgh, April 6, 1857.) XIV. Lecture on the Lamina Spiralis of the Cochlea (Edinburgh Medical Journal, December 1855.) XV. On the Electrical Apparatus in Torpedo, Gym- notus, Malapterurus, and Raia (Edinburgh Medical Journal, August and September 1855.) XVI. A Brief Review of the Present State of Or- ganic Electricity ..... (Edinburgh Philosophical Journal, October 1855.) Page 205 220 231 246 265 273 282 289 306 CONTENTS. vii Page XVII. On the Conferva which vegetates on the Skin of the Gold-Fish ..... 345 (Annals and Magazine of Natural History, IX., 1842.) XVIII. History of a Case in wmcn a Fluid periodi- cally EJECTED FROM THE STOMACH CONTAINED Vegetable Organisms of an undescribed form (Sarcina Ventriculi) . . . .351 (Edinburgh Medical and Surgical Journal, LVII., 1842.) XIX. On a Diseased Condition of the Intestinal Glands ...... 372 (Edinburgh Monthly Journal of Medical Science, April 1842.) XX. Structure and Pathology of kidney and liver 379 (London and Edinburgh Monthly Medical Journal, May 1842.) Anatomical and Pathological Observations. — Edin. 1845. XXI. Centres of Nutrition .... 389 XXII. The Structure and Functions of the Intes- tinal Villi ..... 393 XXIII. Absorption, Ulceration, and the Structures ENGAGED IN THESE PROCESSES . . . 403 XXIV. The Process of Ulceration in Articular Car- tilages ...... 408 XXV. Secreting Structures . . . .412 XXVI. The Testis and its Secretion in the Decapo- dous Crustaceans .... 429 XXVII. The Structure of the Serous Membranes . 436 VIII CONTENTS. Page XXVIII. Structure of the Lymphatic Glands . . 439 XXIX. The Structure of the Human Placenta . 445 XXX. The Structure and Economy of Bone . 461 XXXI. The Mode of Reproduction after Death of the Shaft of a Long Bone . . .465 XXXII. The Mode of Reproduction of Lost Parts in the Crustacea . . . . .471 XXXIII. Of the Anatomy and Development of TnE Cystic Entozoa . . . . .476 XXXIV. Description of an Erectile Tumour . . 504 (Monthly Medical Journal, 1845.) XXXV. Description of a Congenital Tumour of the Testis ...... 506 (Northern Journal of Medicine, 1845.) XXXVI. The Curvatures of the Articular Surfaces and the General Mechanism of the Hip- Joint ...... 508 EXPLANATION OF THE PLATES. — ♦ — DEVELOPMENT OF THE TEETH.— Plate I. page 1. a. Fig. 1. A tooth-germ— a bulging on a mucous membrane. b. Diagrams illustrating the three stages of dentition. Fig. 1. Follicular. 2. Saccular. 3. Eruptive stage. c. Diagrams illustrative of the formation of a temporary and its corresponding permanent tooth from a mucous membrane. Fig. 1. Mucous membrane. Fig. 2. Mucous membrane, with a gra- nular mass deposited in it. Fig. 3. A furrow or groove on the granular mass. (Primitive dental groove.) Fig. 4. A papilla (a tooth germ) on the floor of the groove. Fig. 5. The papilla enclosed in a follicle in the bottom of the groove (the latter in the condition of a secondary dental groove). Fig. 6. The papilla acquiring the configuration of a pulp, and its sac acquiring opercula. The depression for the cavity of re- serve behind the inner operculum. Fig. 7. The papilla become a pulp, and the follicle a sac, in conse- quence of the adhesion of the opercular lips. The second- ary dental groove in the act of closing. Fig. 8. The secondary groove adherent, except behind the inner operculum, where it has left a shut cavity of reserve for the formation of the pulp and sac of the permanent tooth. Fig. 9. The last change rendered more complete by the deposition of the granular body (the enamel organ of Hunter, Purkinje, and Raschkow). Deposition of tooth substance commencing. Fig. 10. The cavity of reserve receding from the surface of the gum, and dilating it at its distal extremity, in which a pulp is forming. Rudimentary opercula developing near its proximal extremity and dividing it into a follicular and an extra-folli- cular compartment. Temporary tooth pulp nearly covered with tooth substance, and granular body almost absorbed. Fig. 11. The cavity of reserve become a sac with a pulp, and further removed from the surface of the gum. Temporary tooth pulp covered with tooth substance, and granular body absorbed. (See Hunter, Nat. Hist, of Human Teeth, p. 95.) Fig. 12. The temporary tooth acquiring its fang by the triple b X EXPLANATION OF THE PLATES. action described in tbe paper, and its sac approaching the surface of the gunr. Fig. 13. The fang of the temporary tooth longer, and its sac touching the mucous membrane of the mouth. Fig. 14. The temporary tooth sac again a follicle ; free portion of the latter becoming shorter, and fang of the tooth receding from the bottom of its socket. Permanent tooth sac re- moving further from the surface of the gum. Fig. 15. The temporary tooth completed. Free portion of the sac be- come the vascular border of the gum ; adherent portion become what is commonly denominated the periosteum of the fang, but which in fact is a triplex membrane — viz. mucous membrane, submucous tissue, and periosteum of al- veolus or jaw bone. The permanent tooth sac much re- moved from the gum, but connected with it by a cord which passes through the foramen behind the temporary alveolus. Fig. 16. The fang of the permanent tooth lengthening, and the crown approaching the gum Fang of temporary tooth undergoing absorption. Fig. 17. The same change more advanced. Fig. 18. The permanent tooth appearing through the gum. Shedding of the temporary tooth. Fig. 19. The perfected permanent tooth. Fig. 20. The shed temporary tooth. d. Diagrams illustrative of the formation of the three molar teeth from the non-adherent portion of the primitive dental groove. Fig. 1. The non-adherent portion of the primitive dental groove. Fig. 2. The papilla and follicle of the first molar on the floor of the non-adherent portion, which is now a portion of the secondary groove. Fig. 3. The papilla and follicle of the first molar become a pulp and sac. The lips of the secondary grove adhering, so that the latter has become the posterior or great cavity of reserve. Fig. 4. The sac of the first molar increased in size, and advanced along a curved path into the substance of the coro'noid jnocess or maxillary tuberosity. The cavity of reserve lengthened out or advanced along with it. Fig. 5. The sac of the first molar returned by the same path to its former position. The cavity of reserve again shortened. Fig. 6. The cavity of reserve sending backwards the sac of the second molar. Fig. 7. The sac of the second molar advanced along a curved path into the coronoid process or maxillary tuberosity. The cavity of reserve lengthened for the second time. Fig. 8. The sac of the second molar returned to the level of the dental range. The cavity of reserve shortened for the second time. EXPLANATION OE THE PLATES. XI Fig. 9. The cavity of reserve sending off the pulp and sac of the wisdom tooth. Fig. 10. The sac of the wisdom tooth advanced along a curved line into the maxillary tuberosity or coronoid process. Fig. 11. The sac of the wisdom tooth returned to the extremity of the dental range. MUSKET-BULLETS IN TUSKS OF ELEPHANTS. Plate II. page 56. Fig. 1. A portion of a section of a wounded tusk ; a cement ; 6 regular ivory deposited previous to the wound ; c irregular ivory deposited after the wound. Fig. 2. A diagram illustrative of the mode of connection between the Retzian tubes of the primary and secondary regular ivory, and the -cells and Retzian tubes of the different inosculating systems of the irregular ivory, after inclosure of a ball ; a cement with its osseous corpuscles ; b primary regular ivory with its Retzian tubes ; c the ball ; d the irregular ivory with its systems of tubes and cells ; e secondary regular ivory Fig. 3. A copper ball inclosed in a sphere of irregular ivory, on the surface of which are the orifices of Haversian canals. Some of the orifices have closed, and present the appearance of irregular projections. The mass has begun to be attached to the regular ivory of the tusk, and would in time have been inclosed in it. The ball must either have passed across from the opposite side of the tusk, or must have sunk below the level of the hole by which it entered. Fig. 4. Section of a tusk across the cavity of 'which a baU has passed, and become inclosed in the ivory of the waR opposite the hole by which it entered. The hole is fiUed with irregular ivory, coated extemaUy with cement. The cement over the ball has been disarranged by the shock. This section proves that the track of a ball across the pulp is not necessarily ossified. Fig. 5. Section of a tusk across the base of which a spear-liead has penetrated and remained in the wound. The weapon has therefore been separated from the pulp by deposition of irregular ivory in the form of a tube ; a cement ; b b ir- regular ivory deposited previous to the wound ; c c regular ivory deposited after the wound ; d irregular ivory inclosing a vacant space e, the seat of an abscess or sinus, and con- tinuous with the cavity of f, a mass of irregular ivory (coated with regular ivory) in the form of a tube surrounding the foreign body. As irregular ivory always contracts in drying, more than any other kind of dental substance, that portion of the section marked g g has been bent outwards. Fig. 6. The same section viewed in profile ; a the broken shaft of the Xll EXPLANATION OF THE PLATES. spear ; i an irregular mass of cement formed round the orifice of the wound by the membrane of the tusk follicle, and which would have closed the wound had the weapon been removed. The wound inflicted has in this instance, as in many others, stunted the growth of the tusk at c c, so as to render the part formed after the injury narrower and weaker. Fig. 7. A longitudinal section of a tusk in which a gun-shot wound had terminated in abscess of the pulp ; a a cement ; b b regular ivory deposited before the injury ; c c regular ivory deposited after the injury ; d d irregrdar ivory bound- * ing the abscess ; e e masses of cement and irregular ivory at the margin of the shot-hole. Fig. 8. The external aspect of a portion of a tusk, which had been transversely fractured ; a a the line of fracture united exter- nally by irregular masses of cement. Fig. 9. The internal aspect of the same portion of tusk ; a a the line of fracture united by irregular ivory, a portion of which is arranged in a reticular form. This reticular ivory is interest- ing, as affording a natural analysis of the peculiar arrange- ment of parts in the irregular ivory described in the paper. Each bar of the reticular ivory is traversed longitudinally by a medullary canal, from which radiate secondary canals and Eetzian tubes, the whole being coated with regular ivory. This reticular ivory differs from the ordinary form of ossified pulp, only in the greater distance between the Haversian or medullary canals, so that portions of the pulp have remahied unossified between them. DEVELOPMENT OF THE SUPRA-RENAL, TPIYMUS, AND THYROID BODIES.— Plate III. page 66. Fig. 1. A portion of an early embryo of the sheep. a. Heart. 1. Lungs still in front of the intestinal tube. c. Wolffian body. d. Lateral mass of blastema, out of which is formed the supra- renal capsule, thymus, and thyroid. e. Cardinal vein. /. Jugular vein. g. Ductus Cuvieri. Fig. 2. A portion of the early embryo of the sheep. a. Intestinal tube and ductus vitelli. b. Liver. c. Omphalo-mesenteric vein. d. Omphalo-mesenteric artery. e, f. Mass of blastema on the inner side of the Wolffian body, and EXPLANATION OF THE PLATES. v i i i around the trunks of the omphalo-mesenteric vessels ; this is the posterior part of the lateral mass of blastema marked d in Fig. 1, and becomes in the course of development the supra-renal capsule. Fig. 3. An early embryo of the sheep. a. Head, branchial arches, and rudiment of the eye. b. Heart. c. Ductus Cuvieri entering the auricle, and receiving d. The jugular, and e. The cardinal vein. /. The lateral blastema. g. Wolffian body. h. Umbilical cord, to which is passing i. The allantois. j. The omphalo-mesenteric artery, and k. Omphalo-mesenteric vein ; traces of the umbilical vessels are also seen in the parietes of the abdomen. l. The liver and intestinal tube. m. Lungs. Fig. 4. Jugular veins and lateral masses of blastema in the sheep, soon after the latter have joined across the middle line. a. The triangular absorption of the cervical portion, which is the first indication of the separation of the thyroid. Fig. 5. The next stage, in which the thyroid is more distinct. Fig. 6. The thyroid is now quite distinct, and differs from the thymus in being opacpue ; the latter exhibits opacpue spots in a semi- transparent matrix. Fig. 7. The thyroid and thymus have assumed their perfect form. Fig. 8. A portion of the supra-renal capsule of the adult green monkey, slightly compressed. It exhibits the minute nucleated par- ticles of which it consists. Among these, at pretty regular distances, are seen the germinal spots. Fig. 9. A portion of the thymus of the brown bear, slightly compressed. It exhibits the nucleated particles of which it consists. These are grouped in spherical masses around centres from which they appear to have derived their origin. Fig. 10. A portion of the thymus from a human fcetus. It has been taken from the surface of the gland, so as to exhibit the areolar fibres which form its delicate capsule. The pressure of the glass plates has almost obliterated the spherical grouping in the cells. Fig. 11. A portion of the membrane which covered the contiguous sur- faces of the lobes of the thymus of a human foetus (the membrane lining the reservoirs of Sir A. Cooper). It has the same structiu-e as in Fig. 10. It exhibits no germinal membrane, but consists of an areolar or fibrous texture inter- mixed witli the cells of the organ, the fibres being more XIV EXPLANATION OF THE PLATES. fasciculated, and running a straigliter course than in the substance of the organ. Fig. 12. A portion of the thyroid from a human foetus, slightly com- pressed. It exhibits the same structure as the thymus, but its fibrous texture is more developed. Fig. 13. A portion of the same thyroid to show its vascular network, in the meshes of which, as in Fig. 12, the cells are seen arranged in groups. CENTRES OF NUTRITION.— Plate IV. page 389. Fig. 1. A portion of the middle and internal membranes of a large encysted tumour situated under the tongue, and removed by Professor Syme. a. The middle or second membrane, which is a germinal membrane, consisting of flattened cells, the lines of junction of which are faintly visible, the nuclei remaining as the germinal spots of the membrane. b. The internal membrane, a layer of small cells, somew’hat spherical, ■with slightly granular contents. The external membrane of the cyst, consisting of areolar and elastic fibres, contained the blood-vessels of the morbid growth. The cyst contained a soft mass resembling thick honey in consistence. The outer layer of this mass was -white, and consisted of large, flat, transparent cells or scales, with few or no traces of nuclei. The larger internal part of the mass was reddish-grey, and consisted of ovoidal cells, resembling those of the external layer, except that they were turgid with a transparent oily-like fluid, and contained nuclei in various stages of development. Fig. 2, a. Fig. 3, a. Cells of the meliceritous mass — those without nuclei being those of the white external layer, the others belonging to the reddish-grey part of the mass, presenting nuclei in various stages of development. b b. Some of the latter cells, in which the nuclei have become so much developed as to distend their cells beyond the average size. In these enlarged cells, it will be remarked that the nuclei, instead of remaining as single germinal spots for each cell, have broken up into numerous spots or centres of nutrition. In a tumour of this kind, the cyst and its contents are two distinct parts, and perform two distinct actions. The cyst is the active agent in withdrawing materials of nutrition for itself and its contents from the vessels which ramify in its outer tunic. The organs which accomplish this are the germinal spots in its middle tunic, which, in virtue of forces EXPLANATION OF THE PLATES. XV of attraction in each, select and remove from the capillary vessels the matter necessary for the formation of the cells of the internal layer. These after solution pass in succession into the cavity of the cyst, to serve as nutriment for the contained cellular mass. This mass is evidently the principal element of the morbid growth. The cyst is a subsidiary or accessory part, arranged for the protection and due supply of nourishment for its principal. The cells of which this mass consists have each its own nucleus or germinal centre. These cells would appear to be of two classes — those whose nuclei produce young cells in their interior for their own nutrition, but not for the reproduction of new mother-cells, and those which act as reproductive individuals for the whole morbid growth. These latter cells are marked b b in Figs. 2 and 3, and con- tain numerous nutritive centres or germinal spots in their interior. The flat cells of the white external layer appear to be those individuals of the first class, which are about to close their existence, their nuclei having disappeared ; their food, therefore, no longer supplied to them, and their position in the mass removed to the exterior by the eccentric development of the younger and more active neighbouring cells. In a morbid mass of this kind, as in the textures and organs of an animal generally, certain parts are set aside as reproducers, the remaining parts performing the functions of the whole mass, texture, or organ ; just as in certain com- munities of animals certain individuals are set aside to re- produce the swarm, the others are devoted to the duties of the hive. Fig. 4. Two portions of the primary or germinal membrane from the tubes of the tubular portion of the human kidney. The germinal spots of the gland are seen imbedded in the sub- stance of the membrane. The external layer of this mem- • brane, which may occasionally be seen with the nuclei detached from it, is the basement or homogeneous membrane of Mr. Bowman. In other instances, as when the epithelia are but slightly developed, it becomes difficult to decide whether we have merely the germinal membrane, or both the membrane and its epithelia before us. INTESTINAL VILLI.— Plate IV. page 389. Fig. 5. Extremity of a villus immediately before absorption of chyle has commenced. It has cast off its protective epithelium, and displays, when compressed, a network of peripheral lacteals. The granular germs of the absorbing vesicles, as yet undeveloped, are seen under its primary membrane. XVI EXPLANATION OF THE PLATES. Fig. 6. Extremity of a villus, with its absorbent vesicles distended with chyle, and the trunks of its iacteals seen through its coats. Fig. 7. Protective epithelium-cells from a villus in the dog* Fig. 8. Protective epithelium-cells cast off preparatory to absorption of chyle ; instead of nuclei, they present, in their interior, groups of globules. Fig. 9. A group of the same cells adhering by their distal extremities. Fig. 10. Secreting cells thrown out of the follicles of Lieberkiihn during digestion. Fig. 11. Diagram of mucous membrane of jejunum when absorption is not going on. a. Protective epithelium of a villus. b. Secreting epithelium of a follicle, c c c. Primary membrane, with its germinal spots or nuclei, d d. e. Germs of absorbent vesicles, f. Vessels and Iacteals of villus. Fig. 12. Diagram of mucous membrane during digestion and absorption of chyle, a. A villus, turgid, erect ; its protective epithelia cast off from its free extremity ;+ its absorbent vesicles, its Iacteals and blood-vessels turgid, b. A follicle discharging its secreting epithelia. PROCESS OF ULCERATION IN ARTICULAR CARTILAGE. Plate IV. page 389. Fig. 13. a. A section of articular cartilage and absorbent membrane. In the lower part of the section the cartilage - corpuscles retain their natural size and appearance ; as they approach the rugged ulcerated edge, they increase in size, and contain numerous young cells, apparently the progeny of their nuclei ; beyond this edge, rounded masses of cells, originally con- tained within the cartilage-corpuscles, are seen embedded in the ceUular absorbent mass. b. Absorbent ceUs of the false membrane, with two globular masses derived from the cartilage-corpuscles. SECRETING STRUCTURES.— Plates IV. V. Plate IV. page 389. Fig. 14. Four secreting cells from the ink-bag of Loligo sagittata. Fig. 1 5. Five cells from the liver of Patella vulgata. In this instance the bile is contained in the cavities of the secondary cells, which constitute the nucleus of the primary cell. * It may he noted that both in figures 7 and 9 the clear space at the broad free ends of the columnar intestinal epithelial cells, to which several German anatomists have recently directed attention, is figured by the author. — Eds. + The author subsequently abandoned the idea that the epithelial cells were cast oft' during absorption. — Eds. EXP LAN ATION OF THE PLATES. xvii Fig. 16. Three cells from the kidney of Helix aspersa. The contained secretion is dead white, and presents a chalky appearance. Fig. 17. Two cells from the vesicles of the testicle of Squalus cornubicus. The contained bundles of spermatozoa are developed from the nucleus — each spermatozoon being a spiral cell. Plate V. page 412. Fig. 1. Five cells from the mamma of the bitch. In addition to their nuclei, these cells contain milk-globules. Fig. 2. A portion of duct from the testicle of Squalus cornvibicus. A few nucleated cells, the primary or germinal cells of the future acini, are attached to its walls. Fig. 3. The primary cell of an acinus in a more advanced stage. The nucleus has produced a mass of yoirng cells. The pedicle appears to have been formed by the germinal cell carrying forward the wall of the duct. A diaphragm accordingly presents itself across the neck of the pedicle. Fig. 4. A primary cell in a more advanced stage. Fig. 5. A primary cell still more advanced. Fig. 6. Some of the secondary cells, products of the nucleus of the primary cell, are cylindrical, and are arranged in a spiral. Fig. 7. The change into cylinders, and the spiral arrangement com- pleted. Fig. 8. a. One of the secondary cells ; its nucleus a mass of young cells. b. A secondary cell elongated into a cylinder, each cell of its composite nucleus elongated into a spiral, c. The^piral cells or spermatozoa, free. Fig. 9. A bunch of acini, in various states of development, maturity, and atrophy. The four following figures are diagrams, arranged so as to illus- trate the intimate nature of the changes which occur in vesi- cular glands when in a state of functional activity. Fig. 10. A portion of gland-duct with two acini. One of the acini is a simple primary cell ; the other is in a state of develop- ment, its nucleus producing young cells. Fig. 11. Both acini are advancing; the second has almost reached maturity. Fig. 12 The second acinus is ready to pour out its contents, the first to take its place. Fig. 13. The second acinus is in a state of atrophy, the first is ripe. Fig. 14. Two follicles from the liver of Carcinus mcenas. The colour- less germinal spot is at the blind extremity of the follicle. The secreting cells become distended with bile and oil as they recede from the germinal spot. xvm EXPLANATION OF THE PLATES. THE STRUCTURE OF THE LYMPHATIC GLANDS. Plate Y. page 412. Fig. 15. A portion of the germinal membrane of the human intra- glandular lymphatics, with its germinal spots or nutritive centres diffused over it. Fig. 16. A portion of the same membrane, in which the component flattened cells, with the centres, have been rendered trans- parent, and are beginning to separate, by the action of acetic acid. Five of the glandular epithelia adhere to the mem- brane. Fig. 17. A diagram of a lymphatic gland, showing the intra-glandular network, and the transition from the scale-like epithelia of the extra-glandular to the nucleated ceUs of the intra- glandular lymphatics. Fig. 18. A portion of an intra-glandular lymphatic, showing along one edge the thickness of the germinal membrane, and upon it the thick layer of glandular epithelia. THE STRUCTURE OF THE PLACENTA.— Plates V. VI. Plate Y. page 412. Fig. 19. The extremity of a placental villus. a. The external membrane of the villus, the lining membrane of the vascular system of the mother. b. The external ceUs of the villus, cells of the central portion of the placental decidua. c c. Germinal centres of the external cells. d. The space between the maternal and foetal portions of the villus. e. The internal membrane of the villus, the external membrane of the chorion. f. The internal cells of the villus, the cells of the chorion. (j. The loop of umbilical vessels. Fig. 20. This drawing illustrates the same structures as the last, and has beenhntroduced to show the large space which occasionaUy intervenes between the internal membrane and the external cells. It would appear that into this space the matter separated from the maternal blood by the external cells of the villus, is cast before being absorbed through the internal membrane, by the internal cells. This space, therefore, is the cavity of a secreting follicle, the external ceUs being the secreting epithelia, and the maternal blood-vessel system the capillaries of supply. This maternal portion of the villus, and its cavity, correspond to the glandular cotyledons of the ruminants, and the matter thrown into the cavity to the milky secretion of these organs. EXPLANATION OF THE PLATES. XIX Fig. 21. A portion of tie external membrane, with external cells of the villus. a. Cells seen through the membrane. b. Cells seen from within the villus. c. Cells seen in profile along the edge of the villus. Fig. 22. The extremity of a villus treated with acetic acid. All the parts are distinctly visible, and the germinal centres of the internal cells are seen surrounding the umbilical vessel. Fig. 23. A villus with a terminal decidual bar, along the cavity of which the external cells are seen to be continued, so as to pass forwards in the direction of the parietal decidua. Plate VI. page 445. Fig. 1. A portion of the external membrane of a villus, with a lateral decidual bar. This portion of membrane is seen from its fcetal aspect, and in this three or four germinal centres of the external cells are perceptible. Fig. 2. A drawing of the extremity of a villus treated with acetic acid. In this villus all the parts described are distinctly seen, and indicated by the same letters as in Fig. 19, Plate V. Fig. 3. The extremity of a villus, with a terminal decidual bar, treated with acetic acid, to show the nuclei of the decidual cells in the cavity of the bar, and on the external membrane of the villus. Fig. 4. Two tufts connected by a terminal decidual bar. Fig. 5. A tuft with a lateral bar passing off from its stem. Fig. 6. A diagram illustrating the arrangement of the placental decidua. a. Parietal decidua. b. A venous sinus passing obliquely through it by a valvular opening. c. A curling artery passing in the same direction. d. The lining membrane of the maternal vascular system, passing in from the artery and vein lining the bag of the placenta, and covering e e the foetal tufts, passing on to the latter by two routes, first by their stems from the foetal side of the cavity, and secondly by the terminal decidual bars f f from the uterine side, and from one tuft to the other by the lateral bar g. Throughout its whole course this membrane is in contact with decidual cells, except along the stems of the tufts, and the foetal side of the placenta, where the decidual cells have degenerated into fibrous or areolar fibres. All that portion of the decidua which is in connection with the bars, villi, and tufts, is the central or functional portion of the decidua, and along with the lining membrane of the maternal vascular system, or external membrane of the tufts, constitutes the true maternal portion of the placenta. XX EXPLANATION OF THE PLATES. h. Two diagrams illustrating tlie fcetaJ cellular elements of the placental tufts. These are the internal membrane, and the in- ternal cells of the tufts, and along with the loops of umbilical blood-vessels constitute the true foetal portion of the placenta. THE TESTIS AND ITS SECRETION IN THE DECAPODOUS CRUSTACEANS.— Plates VII. VIII. Plate VII. page 429. Fig. 1. Figures of Entozoa from the tubuli seminiferi of Orchestia littoralis, probably aUied to filaria, and supposed by M. Kolliker to be the spermatozoa. This opinion, however, is incorrect, as may be seen in the accompanying draw- ings, where figures are given representing all the details of the development of the true spermatozoa. These are all produced from ceHs, whereas the entozoa under considera- tion are never seen within ceUs, but are in all cases generally seen floating free in the seminal vessels. These filaria have only been seen, so far as I am aware, in Amphipoda and Isopoda. If they are spermatozoa, they must be produced from cells ; and from what has been stated in the text, it wiU be seen that in all the Crustacea, these ceUs, before pro- ducing the spermatozoa, undergo several metamorphoses ; and that the final changes take place in the spermatheca of the female, where the seminal animalcules are produced. In Amphipoda and Isopoda, where these supposed filaria exist, we always find them high up in the testicle, and not occa- sionaUy, but in great numbers. In the tertiary seminal cells also, which are floating about among them, not the slightest vestige of the worm can be observed. I am inclined to sup- . pose, therefore, that these thread-like worms, supposed by Kolliker to be spermatozoa, are only parasites. Fig. 2. Representation of a primary germinal cell projecting from the waU of the seminal tube. It has just burst, and the young secondary ceRs are escaping and descending the tube ; during the descent they increase in size, from their nucleus throwing off nucleoli, the latter forming the tertiary generation. In this figure it will be observed that the cell-walls of the parent are quite smooth and unbroken, so that in ail proba- bility the young arise from that portion of the cell attached to the seminal tube. Fig. 3 Is a small quantity of the fluid from the spermatheca of the female crab, showing the tertiary or spermatozoal cells after they have burst from the secondary. As described in the text, the spermatheca appears to be the organ in which the seminal fluid undergoes the final and essential change which fits it for impregnation. EXPLANATION OF THE PLATES. XXI Fig. 4. This figure shows the adult seminal secondary cells from the dilated parts of the seminal tube. They are full of tertiary cells. The fluid amongst which they are floating is thick and albuminous, much more so than it is higher up or lower down the tube, and the large, clear, transparent-looking masses, are the pabulum for the nourishment of the cells It is much more abundant in this part of the organ than any- where else, and accordingly great numbers of the secondary cells, in all stages of development, are constantly found here. If a small cpiantity of the seminal fluid from that portion of the testicle immediately preceding the dilated part be placed under the microscope, it will be seen that the nuclei of the se- condary cells are just throwing off small nucleoli, and that the parent cell is not very much larger than when it burst from the primary. In the same part also, little or no pabulum is ob- served. As we proceed downwards, however, we find them increasing rapidly in size ; and, at the same time, an immense quantity of pabulum floating about in large masses. The lower part of the tube and the vas deferens are almost desti- tute of pabulum, the cells being satiated. Fig. 5. The secondary cells of Hyas araneus from the vas deferens. The walls of the parent cells are remarkably thin. The parent secondary cells are of enormous size in this species. Fig. 6 Represents the testicles of Carcinus mcenas, of the natural size, and shortly before they have reached the maximum state of development. The portion included between a a is the tubular or hepatic, that between b b is the dilated or gastric. The vasa deferentia are not seen in this species so well as in Ilyas araneus, Fig. 8, c c. It is in the gastric division that the pabulum lies in such quantities. Fig. 7 Is the internal or sheathed portion of the external organs of Cancer pagurus ; proximal extremity. Fig. 8. Testes of Hyas araneus. a a. Tubular portion, b b. Follicular portion, c c. Vasa deferentia. Fig. 9. External organs of Cancer Pagurus. a. Is the internal or sheathed portion in situ. b. Is the sheath or external portion. Fig. 10. External organs of Hyas araneus. A. Sheath. B. Sheathed portion. Plate VIII. page 431. Fig. 1. First stage of development of secondary seminal cell of Gala- thea strigosa. Figs. 2, 3, 4. Second, third, and fourth stages of development of the secondary cell. Figs. 5, 6, 7, 8, 9, 10, 11, 12, 13. Various stages of development of the secondary cell of lobster. Figs. 14, 15, 16, 17. The same treated with acetic acid. XXII EXPLANATION OF THE PLATES. Fig. 18. Tertiary or spermatozoal cells. Fig. 19. Secondary cell of lobster seen from armed extremity, to show the three setae. Fig. 20. Primary cell, or caecum of testicle of Pagurus bernhardus full of secondary cells, c. Attachment, b. Free extremity, a. Nucleus. Fig. 21. Primary seminal cell of Pagurus bernhardus filling with se- condary cells. As already described, these cells grow in pairs from discs on the walls of the seminal tubes, and hang free in the cavity of the tube. It has also been described how the secondary cells are produced from the parent nucleus, namely, by means of successive growths, each of which carries off a fold of nucleus before it. a. Disc from which the primary seminal cells grow. bb. The discs on each side of it. c c. The origins of the primary seminal cells. d. One of the primary cells cut off. e. Nucleus of the primary cell in a state of activity ; it has just thrown off a series of young, marked f In the diagram. g. Are several old walls of former growths. h. Full extremity of primary cell. Fig. 22. A small portion of the testicle of Pagurus bernliardxis magni- fied, showing the manner in which the cseca hang from the walls of the seminal tube. Fig. 23. Small drop of seminal fluid of lobster, showing the secondary cells before the armature had expanded. Fig. 24. Small drop of seminal fluid of lobster from vas deferens. That part of the figure above a a, as seen under the micro- scope, presents one dense mass of secondary cells floating down towards b, where a few are seen separate. Fig. 25. A caecum from the testicle of Carcinus mcenas, showing a ger- minal spot at its apex just being filled with secondary cells. Fig. 26. The germinal spot enlarged. REPRODUCTION OF LOST PARTS IN THE CRUSTACEA. Plates IN. NIL Plate IN. page 471. Fig. 1 Represents the raw surface of the proximal or adherent portion of the leg of Cancer 'pagurus , after the animal has thrown off the distal portion. The figure represents the parts of the natural size, and only a few hours after the separation had taken place. Fig. 2 Is a representation of the same part, after the young leg had grown to some size. It null be observed that the cicatrix, which was formed upon the raw surface a few hours after EXPLANATION OF THE PLATES. xxiii separation, lias now become very strong, covers the young germ, thus acting as a means of defence from external injury. Figs. 3, 4, 5, Are the same parts in progressive states of development. Fig. 5 presents a bifurcated character ; probably from some accidental cause it thus appears smaller than it is in the normal state. Fig. 6 Represents the raw surface of the leg, already alluded to in Carcimis mcenas, some time after separation. A nucleated cell is seen in the centre. This drawing was made from a very small specimen, and was only procured in the stage re- presented after great difficulty. Fig. 7 Represents a longitudinal section of a very young germ, for the purpose of showing its mode of development. The fibrous- looking band which surrounds it externally, is a circular canal which belongs to a system of vessels described in the text. The four striated bodies which Re next to this canal are the rudiments of the four joints of the future limb. The striated appearance arises from the muscles already so far developed, and the albuminous matter within, and which they enclose, appears to be pabulum for their farther nourishment. The more defined globules, which may be observed floating amongst the albumen, are oil-globules. In the development of this leg, it will be observed that the external segments, or those which are analogous to the thigh and first tibial joints, are largest and most fuUy formed, — a fact we would be led to expect, from the circumstance of their formative cells being the first thrown off from the original parent nucleus, and consequently the first that would take on a central or more independent action. From a similar mode of development, we see that the second tibial and tarsal joints are the smallest, as they are the last formed of the centres. The last or distal phalanx is the smallest of the internal segments ; those nearest the circular vessel are the largest, as was to be ex- pected from the centres which formed them, being the oldest and the first formed from the earRer generations of ceHs ; and those again within them are smaUer, being formed from the later generations thrown off by the original parent. Fig. 8. Cells from the external series represented by c in Fig. 9. Fig. 9. Transverse section of raw surface of proximal or attached ex- tremity of the reproductive organ in leg of Cancer pa gurus. This is the surface and appearance which is seen immediately upon the leg fading off ; if it is seen half-an-liour, or a little more, after the separation, it is covered with a thickish film, which shortly becomes a strong opaque cicatrix hiding every- thing beneath it. The vessels seen in Fig. 15 are also omitted, for the purpose of showing the structure of the re- productive body more clearly. XXIV EXPLANATION OF THE PLATES. a. Is the circular vessel, of the system of vessels mentioned in the text, and it surrounds b. A fluid or semi-fluid mass, containing small nucleated cells, from which the germ is probably derived. c. Is a large mass of very large cells surrounding the circular vessel, which appear to act as a magazine of nutritive matter for the young germ during its growth. d. Is the shell membrane, which is surrounded externally by the shell. Fig. 10. A young limb of Carcinus mcenas still enclosed within its original cyst, which is formed probably from the cicatrix mentioned above. Magnified two diameters. Fig. 11 Is a very young leg of the common lobster. The reproduced leg of this species is not enclosed in a cyst, and it is not folded upon itself, but projects straight forward. Nat. size. Fig. 12 Is a figure of the natural size of one of the large claws of Pagurus bernhardus, shortly after it has burst from its con- taining cyst. Fig. 13. Enlarged view of Fig. 11. Fig. 1 4. One of the large claws of Carcinus manias still enclosed within the cyst. From observations made, it appears that these young legs remain within the cyst until their own covering or shell is of sufficient strength to act as a means of defence. They do not obtain a true shell for some time after the cyst has burst. Fig. 1 5. Raw surface of proximal extremity of leg in Cancer jiagurus, shortly after the animal has thrown off the distal portion. This figure is made for the purpose of showing the distri- bution of the peculiar vessels, and their mode of running from the circumference towards the circular vessel in the centre. Fig. 16. Longitudinal section of young leg still within the cyst. a. Part of old leg containing the reproductive organ. b. External cells. c. Smaller nucleated cells. d d. Cyst of young leg. e. Femur of young leg. /. First tibial joint of young leg. g. Second tibial joint. h. Tarsal joint. Fig. 17. Natural size of young leg. Fig. 18. Portion of blind extremity of one of the peculiar vessels which are attached to the blood-vessel running to the leg, Plate XII. Fig. 14. The contents are oil-globirles, but in the figure have somewhat the appearance of nucleated cells. Fig. 19. An enlarged view, for the purpose of showing the connection of these vessels. EXPLANATION OF THE PLATES. XXV Fig. 20. Two of the blind extremities from raw surface of leg, where they present a clavate appearance. Fig. 21. View of the extremity, showing the dark spot supposed to he a germinal spot. Plate XII. Fig. 9. Small longitudinal portion of shell from the large claw of Cancer pagurus, showing the thickness of the annulus or ring in it at the point of separation. Fig. 12. Longitudinal section of one of the legs of Cancer pagurus, showing the natural position and relations of the reproductive organ. a a. Femur. b b. Reproductive organ. c. Natural appearance of line of separation cl. Coxa. Fig. 13. Enlarged foramen as it is seen on raw surface after the separa- tion. This has been hardened in boiling water, which gives it a much more defined appearance, and also enlarges it more than it naturally should be. Fig. 14 Is a small portion of the femoral artery, aboitt half-an-inch in extent beyond the line of separation, which is covered as re- presented by the pecrdiar vessels. a. Distal extremity of blood-vessel. ON THE ANATOMY AND DEVELOPMENT OF THE CYSTIC ENTOZOA.— Plates VI. X. XI. XII. Plate X. page 476. Fig. 1. Magnified view of one of the young of Acepkalocystis armatus still attached to the germinal membrane of a secondary parent. It is taken from the grorrp shown in Fig. 2, and is still in an early stage of development, the circlet of teeth still being minute and not fully developed. The absorbing series of cells may be seen internally. Fig. 2. Small portion of the germinal membrane of a secondary parent of Acepkalocystis armatus highly magnified. Fig. 3. Small portion of germinal membrane of Acepkalocystis armatus in a state of degeneration ; nothing is seen in the membrane, which is quite homogeneous, except the small cells figured a. b. Is the commencement of one of the cretaceous fatty masses described in the text. Fig. 4. Several of the stages of development of Cysticercus. a. First stage represents spines ; hardly if at all seen. b. Their first decided appearance. c. Third stage. c XXVI EXPLANATION OF THE PLATES. d. Fourth, stage. Fig. 5. Small portion of the germinal membrane of Aeephalocystis armatus. Fig. 6. Small portion, highly magnified, of the granular matter from the cyst of Cysticercus. Fig. 7. Small portion of the inner surface of the external membrane of Aeephalocystis armatus while in a state of degeneration. Fig. 8. Ovum from the pedicle of Cysticercus. Fig. 9. Small portion of the germinal membrane of Aeephalocystis monroii, highly magnified. a. Fibrous basis. h. Germinal vesicles. c. Secondary acephalocysts within the germinal vesicles ; this portion was taken from the large parent cyst, which is the primary animal, buried in the liver ; and each of the smaller vesicles marked c belong therefore to the secondary genera- tion, their progeny again being the tertiary generation. Fig. 1 0 Is a specimen of Cysticercus neglectus ruptured at the fundus of the sac, apparently for the escape of the- young germs into the cavity of the cyst, where they become attached. Fig. 11. Small portion of the cyst of Cysticercus neglectus magnified, showing its vascularity, and the mode of attachment of the young Cysticerci to its internal surface. Fig. 12. View from above the pedicle of Cysticercus, showing the dis- position of the teeth. In all works hitherto published on Helminthology, there has been a great want of proper figures or descriptions of the true generic and specific characters of these animals, a point of the utmost importance for obtaining a proper knowledge of them : with this view the author has paid scrupulous attention to the leading characters, and these he has placed in the form of a synopsis at the end of the chapter. All the drawings have been made with the view of illustrating these characters more fully. The disposition of the teeth, and their forms, are perhaps the most certain ex- ternal characters. Plate XI. page 482. Fig. 4. Magnified view of a small portion of the external or tubular membrane of DisJsostoma aeephalocystis. a. Larger disc. b. Smaller one on its surface. c. Tubuli. d. Extremities of tubes. e e. Gemmules, which at this stage of development may act as absorbents. Fig. 5. Natural size of Ciskostoma aeephalocystis. Fig. 6. Diskostoma aeephalocystis in various stages of development. EXPLANATION OF THE PLATES. XXV11 a a a. Small cells arising from the attached surface of the tubular membrane. This is the manner in. which the original group increases in size. b. More advanced. c. First stage of second mode of development, or that for the extending of the parasite to as yet uninfested parts of the body, for the purpose of forming new groups. d. Second stage. e. Third stage. /. Root where the original germ became fixed. g. External or tubular membrane. Fig. 10. Section of Astoma acephalocystis, showing its internal structure Plate XII. page 487. Fig. 1. Portion of sac of Cysticercus, much magnified. a. Absorbing cells of absorbing membrane. b b. Separate ova, after their escape from the pedicle. Fig. 2. Cysticercus negleclus very much magnified. Fig. 3. Small portion of omentum containing Cysticercus neglectus, showing the bodies considered to he young Cysticerci attached ; the omentum has been folded over, and the young (a) are seen attached to the fold. Fig. 4. The natural size of the animal supposed to be a new Ctenurus — Ccenurus hepaticus. Fig. 5. Magnified view of the head of Acep)halocystis armatus in a more advanced stage than the former figure. Fig. 6. The germinal membrane from which it was taken. Fig. 7. The absorbing membrane of cyst of Cysticercus rattus highly magnified. Fig. 8. Teeth of Cysticercus rattus highly magnified. Fig. 10. Ovum of Cysticercus rattus highly magnified. Fig. 11. Ova from pedicle of Cysticercus rattus highly magnified. Plate YI. page 445. Fig. 8. Gymnorhynchus horridus within its cyst. Fig. 9. exposed. Fig. 10. First stage of Ccenurus cerebralis. Figs. 11, 12, 13, 14. Second, third, fourth, and fifth stages of the dis- coidal period of development of Ccenurus cerebralis. Fig. 15. One of the first stages in the vertical period of development. Fig. 1 6. Sphairidion acephalocystis highly magnified. Fig. 7. Neuronaia monroii. (J. Goodsir.) a. Suctorial mouth. b. Acetabulum. c. Orifice of organs, supposed to be reproductive. d. Posterior orifice, by which the sigmoidal “ eisterna chyli” e. Opens, and apparently also, xxvm EXPLANATION OF TIIE PLATES. f. The thick-wallecl peculiar sac. g. Pyriform sac, a receptacle for the ova. i. Male organs. The figure also presents the arrangement of the dermal spines, and the general form of the animal. Plate XI. page 482. Fig. 2. The anterior extremity and suctorial mouth of Neuronaia monroii more highly magnified. Fig. 7. The cyst of Neuronaia monroii in a bundle of nervous fila- ments. The fissured appearance of the cyst, with its epithelia, is represented in this drawing. I am inclined to believe that the function of the cyst in this and the other Cystic Entozoa is to supply nourishment to the enclosed animal, drawing it from the surrounding parts, and throwing it into the cavity, the structure and action being identical with that in the encysted tumours as already described. The bulbous extremities of the C3 r sts of Trichina spiralis contain masses of germinating cells, to which I am inclined to attribute the same function. Figs. 8, 9, 11. The clavate extremities of the cysts of Trichina spiralis, with their germinating absorbent cells. The epithelium and absorbent cells of the cysts of the entozoa may be considered as permanent yelk-cells in the economy of these persistent embryos. Figs. 1 and 3. Magnified drawingsj of Sarcina ventriculi described, but badly figured by me in the Edinburgh Medical and Surgical Journal, No. 151. I am still of opinion, notwithstanding the arguments of Mr. Busk, in the Microscopical Journal, that this body is a vegetable parasite, its sudden occurrence and sudden disappearance being not more extraordinary than the rapid development of many cellular structures ; the glandular epithelium, for instance, during secretion. That it is a Gonium, as has been suspected by Professor Link, appears to me improbable, as would be admitted, I believe, by that great botanist, if he had had an opportunity of observing its peculiar vegetable aspect, so different from that of an in- fusorial animal. DIVISION I, DEVELOPMENT AND MORPHOLOGY. Vol.ll a. i. Plate. 1 J GonrLsir D&ti' DIVISION I. I.— ON THE ORIGIN AND DEVELOPMENT OF THE PULPS AND SACS OP THE HUMAN TEETH.— Plate I. “ II est pen cle sujets en medecine sur lesqnels on ait tant eerit que sur les dents ; deux cent volumes contiendraient a peine tout ce qu’on en a imprime ! Mais est-ce h dire que tout soit connu a cet egard ? Est-ce a dire que la matiere ait ete epuisee et qu’il ne reste plus rien a faire ? Nullement. L’Anatomie n’a pas encore le dernier mot de la nature sur cet interessant sujet et il reste encore, quoiqu’on en dise, quelques doutes a eclaireir et plus d’une difficulte & resoudre.” — B landin, Anat. du Systeme Dentaire, 1836. Section I. — Examinations of the Dental Arches at Different Ages. 1. An embryo (Fig. 1), which measured 7i lines from the vertex to the point of the coccyx, weighed 15 grains, and appeared to be about the sixth week,* was selected and prepared for the purpose of examining the state * It is difficult to determine the exact age of an embryo. The ages given in the text, therefore, must be considered as approxi- mations, being probably rather under-rated. I have given a full-sized sketch of the youngest subject in which I have observed any of the phenomena of dentition, with the weight and measurements of a few of the others. In researches of this kind, the sequences of phenomena are of more importance than their periods of appearance. Yelpeau, Embryologie ou Ovologie Eumaine ; Bresehet, Etud.es Anatomi- ques, etc., de Vceuf dans Vcspece Humaine: Soemmering, leones Embry onum Humanomm. Fig. l. B 2 ON THE ORIGIN AND DEVELOPMENT OF THE of the palate and dental arches. The cheeks were divided transversely from the commissures of the lips with fine scis- sors ; the jaws were separated, removed, and fixed to the bottom of a small capsule full of water. The point of the tongue was removed. The configuration of the mouth was then determined by means of a half-inch lens and two needles, bent at the points, and fixed in slender handles. Upper Jaw . — The roof of the mouth was bounded an- teriorly and laterally by the free edge of the lip (a, Fig. 2), which is at this age thin and of great transverse extent. Within the lip (a), but separated from it by a groove (6), to be more particularly described afterwards, there was observed a lobe of a liorse-shoe shape (c), narrow anteriorly at the median line, broader, flatter, and of a rounded form on each side posteriorly. Coming out from above the internal posterior edges of this lobe (c), and firmly adhering to it, two other lobes (d J) were seen ; flat, rounded, and curving backwards and in- wards posteriorly, gradually dis- appearing by pointed extremities anteriorly. From the posterior extremities of each of the lobes now described (d d), and of the horse-shoe lobe (c), a thin semitransparent membranous fold (e e) passed back- ward on each side, attached externally to the sides of the capacious bucco-pharyngeal cavity, bounded internally by a free edge opposed to its fellow of the opposite side, and terminating posteriorly on the lateral walls of the pharynx. Adhering to the inferior surface of each of these folds was seen a smaller lobe (//) somewhat similar to the two last, and situated a little behind them. The needle placed under the folds showed that they were free and floating, except at their exterior or adherent edges, and that they constituted a partial division of the large common nasal, buccal, and pharyn- Fiff 2. PULPS AND SACS OF THE HUMAN TEETH. 3 geal cavity into a superior and an inferior compartment. The upper wall of this common cavity was smooth and flat pos- teriorly (g) ; hut anteriorly it was contracted and terminated in a longitudinal bar (A), which ran forwards to be attached to the superior surface of the horse-shoe lobe at the median line, and to the other parts in that neighbourhood. Under the bar (A) a deep cavity (i i) was seen, which communicated with the exterior of the face by two small foramina, which constituted at this period the whole external nasal organ. As before-mentioned, a groove (A) was observed between the lip (a) and the external edge of the horse-shoe lobe (c). This groove (b) was deep, and its walls and lips were in close apposition. It terminated posteriorly on each side (A A) by becoming more shallow, and curving backwards and inwards on the inferior surface of the membranous folds (e e). There was a median frenum between the lip and the horse-shoe lobe. Lower Jaw. — The under lip («, Fig. 3), resembled the upper, and was separated along its whole extent by a groove ( b ) similar to the one above, from a semicir- cular lobe (c). Anteriorly this lobe (c) was divided into two median large (cl cl), and two la- teral smaller lobules (e c), the whole being firmly adherent to the floor of the mouth in front of the tongue and its frenum , which were both well developed. The lateral parts of the lobe (c) were rather indistinct, but at the point where the free edge of the lip terminated, it extended transversely and posteriorly, became thick and bulbous (//), and exhibited on its surface a narrow shallow groove of a sigmoidal form (g g ), which was continuous with the groove behind the lip. There was a median labial frenum. On the external sides of the membranous folds in the e d 4 ON TIIE ORIGIN AND DEVELOPMENT OF THE upper, and of the posterior parts of the lohe in the lower jaw, the cut surfaces of the cheeks made by the scissors were seen (l l, 1 1). The mucous membrane over its whole extent was thin, and of a greyish-yellow colour, the lobes granular, very friable, and of a dead white. The breadth of the upper alveolar arch was l-i line, and the length of the same was 1 line. 2. The jaws of an embryo which measured 1 inch, weighed 20 grains, and appeared to be about the seventh week, were prepared and examined as in the former case. Upper Jaw. — The free edge of the lip (a, Fig. 4) was not so extended as at the sixth week. The horse-shoe lohe (c) had become broader and more developed pos- teriorly, and anteriorly exhibited three lobules, one median ( m ), and two lateral and anterior ( n n). The two lobes observed on each side of the palate in the former embryo ( d cl, f /, Fig. 2), had disappeared, hav- ing apparently coalesced ; the posterior one (/) being curved forwards to join the anterior ( d ), in the point (s, Fig. 4), while the combined mass had contracted itself towards the front of the mouth within the limits of the horse-shoe lohe (c). The cleft had slightly diminished, but was still of sufficient width to display the whole of the undivided nasal cavity. The lip (a) was so lax as to admit of being moved by the middle. The horse-shoe lohe (e) could also he pressed by the same means inwards and backwards. When these two parts were separated, the mucous membrane was seen to form a duplicature (b), between the lips and a ridge (o), which ex- tended from the posterior part of the dental arch to the outer extremity of the lateral lobule ( n ). (( y. Fig. 4. PULPS AND SACS OP THE HUMAN TEETH. 5 The median portion of the dental arch was formed by the two lateral lobules (n n), which separated the lips from the median lobule (m), and extended also a little on each side of it. The lateral portions of the arch presented externally the ridge (o), formerly mentioned, smooth and convex on its exter- nal surface, internally moulded into three curves, the anterior long and shallow, the second deeper, the third or posterior almost semicircular. Behind the last curve, the internal edge of the ridge formed a deep notch, which swept outward and forward, so as to mould the former into an almost isolated lobule (cj). The ridge now disappeared, but its edge continued backwards and inwards, winding around the posterior extremity of the horse-shoe lobe (c), so as to form a groove (k k, Figs. 2 and 4), on the surface of the soft mucous membrane. The in- ternal division of the lateral parts of the dental arch was formed by three bulgings, apparently productions from the horse-shoe lobe (c), and which were separated from the curves of the ridge ( 0 ), by a groove which was deeper at their sides than in their intervals. The anterior one was lengthened and indistinct, the middle one was more developed, the posterior circular, convex, and altogether isolated. The isolation of this bulging was produced by a longitudinal lobule (r), apparently cut off from the external edge of the horse-shoe lobe (c), and forming a partial inner ridge corresponding with the outer one. This new lobule (r) reached back as far as the posterior extremity of the horse-shoe lobe (c), and terminated an- 0 .. teriorly near the middle of the centre h bulging. >• o o Lower Jaw . — In the situation of the dental arch, there existed a groove (Ji, Fig. 5), very distinct posteriorly, but having no outer lip an- teriorly. The inner lip (m), presented posteriorly a large lobe 6 ON TIIE ORIGIN AND DEVELOPMENT OF THE (n), under which, the needle was easily inserted for a short distance. In the middle, this lip (to) was thin, elevated, and curved over the groove (k). Anteriorly it became broader, and curved still more over the groove, and was divided into two median larger lobules (d), and two lateral smaller (e). Between the two median {d) there was a notch at the attach- ment of the lingual frenum. The outer lip (/) was defi- cient anteriorly, so that the groove was bounded in that situation by the under lip (a), which was loose, free, and turned outwards. Posteriorly the outer lip (/) was well de- veloped, and came out from under the posterior lobe (n) of the inner lip, so as to render the grove (h) pointed, and curved backwards and inwards. This lip (/) extended only about half-way towards the median line, and appeared flat, or in the same continuous plane with the floor of the groove. It was also curved outwards, so as to overhang the labial mucous membrane. The groove presented an elevation (o') of its floor near its posterior extremity. There was a labial frenum. The mucous membrane possessed the same physical properties as at the sixth week. The lobes were not so granular, but tougher and more consistent. Breadth of superior arch l\ line, length 1. 3. The jaws of an embryo at the second month, having tion. The horse-shoe lobe was still perceptible under the /7 ,been prepared in the usual man- ' ner, presented the following ap- pearances : — Upper Jaw . — The lip (a, Pig. 6) was more movable, and its free edge less extended. The cleft in the palate had diminished, exist- ing only as a small angular defi- ciency ( x ) in tlie pendulous por- as a small angular defi- PULPS AND SACS OF THE HUMAN TEETH. 7 form of a bulging (c), represented as turned aside to ex- hibit the objects under it. The lobule (r) had increased in size, so as to extend further backwards, and to appear on the posterior lateral parts of the palate. The median lobule ( m ) had become triangular, the anterior edge being formed by the curve of the palate somewhat pointed in front, the lateral edges being straight and meeting in an angle behind, from which the median line of suture or raphe of the palate proceeded. The median lobule (m) had increased re- latively, the lateral lobules (n n ) only absolutely. The posterior portion of the dental groove (k) was longer, wider, and not so much curved. The bulging or papilla (1) was more distinctly isolated ; and at the anterior extremity of the second curve in the ridge (o), another papilla (2) had appeared as a production from the latter. This papilla (2) was bounded externally by a lamina (jp), which was also a production from the edge of the ridge (o), and was notched at its inner margin, where it was applied to the side of the papilla. The dental groove then terminated in a point, at the outer extremity of the lateral lobule («.). There was a labial frenum. Lower Jaw . — The posterior portion of the dental groove had undergone no material change, but had become deeper, and con- tained in the situation of the ele- vation marked (o, Fig. 5), a distinct / rounded papilla (1, Fig. 7). Fur- ther on, another papilla (2) bounded externally by a notched lamina (a) had appeared. This combined papilla and lamina was exactly similar in its configuration and relations to that marked (2, Fig. 6). The anterior part of the groove had become more distinct, not because it had acquired an outer lip, but because its floor had risen above the level 8 ON THE ORIGIN AND DEVELOPMENT OF THE of the labial mucous membrane. There was a labial frenum. The breadth of the superior arch was If line ; length If. 4. The jaws of an embryo nine weeks old were examined under water. Upper Jaw . — No material change had taken place in the l a ^ configuration of the palate, except that the median lobule (m, Tig. 8), had di- ~ \j£\~ minished relatively, and in the trans- verse direction, while the lateral lobules (n) had increased relatively, and also in the transverse direction. A longitudinal lobule (y), had also appeared on the surface of the median lobule (m). The cleft (x) in the soft palate was smaller. The posterior part of the dental groove was wider. The papilla (1), had become more prominent, and the lips of the groove had almost met before and behind it. The papilla (2) is larger. A little further on, corresponding with the lateral lobule (n), on each side, two papillae (3 and 4), with notched laminae in front of them, had appeared. The centrals (3) , or those on each side of the median line, were the most distinct. Lower Jaw . — The lips of the dental groove had approached so as to require separation by the needle to exhibit its contents dis- tinctly. The papilla (1 or 2, Fig. 9) had undergone little change, but two very indistinct bulgings (3 and 4) had appeared on each side of the labial frenum, the centrals (3) being the Fig. t largest. The breadth of the superior arch was If line ; the length If line. PULPS AND SACS OF THE HUMAN TEETH. 9 5. In an embryo of the tenth week the following ap- pearances presented themselves : — Upper Jaw . — Very little change had taken place in the lateral lobules (n, Fig. 10), or the median (m) and its additional lobule (if). They had all increased absolutely, and if any relative change had taken place, it was in the trans- verse diminution of the median (m) and the movement forward of its additional lobule (y). The palate had advanced anteriorly, so as not only to have encroached in some de- gree upon the median and lateral lobule, but also to have thrown itself into folds immediately behind them. The outline of the horse-shoe lobe (which is represented in the sketch as turned aside to exhibit the dental groove), was still observed. There was an indistinct uvula. The papillae (1 and 2) had sunk completely into follicles, and could only be seen by looking into the open mouths of the latter. The mouth of (1) was bordered by four laminae or lids, that of (2), by' three, as represented in the sketch. The papillae (3 and 4) had not increased much, but their notched laminae had become more distinct. At the posterior extremity of the floor of the dental groove, on the inner side of the lobule (q, Figs. 4, 6, 8, 10), a slight bulging (5, Fig. 10) was seen. The upper lip had receded in the neigh- bourhood of the median line, so as to have s disappeared almost entirely at that spot, — the centre of the upper dental arch being exposed. Lower Jaw . — The bulgings on each side of the median line (3, 4, Fig. 11), which were so indistinct in the last subject, 10 ON THE ORIGIN AND DEVELOPMENT OF T1IE liad become well developed and inclosed in follicles, through the mouths of which they were seen. A similar change was observed in reference to the papilla (2). The follicles had been produced by the stretching across of productions from the outer lip (which was very indistinct) towards similar hut much smaller productions from the inner lip (which was still very prominent). The lines of junction of the septa were visible, and the mouths of the follicles pre- sented an unfinished appearance. The papilla (1) had become surrounded by an incomplete follicle, in consequence of the production of a notched lamina from the outer lip of the groove, which lamina was almost met by a smaller slip of membrane from the inner lip. The breadth of the superior arch was 2 lines, length II line. G. 11 th or 12 tlb week . — Upper Jaw . — The median lobule (to, Fig. 12) had diminished so much transversely, as to have become an- tero-posterior ; while its supplement- ary lobule had become attached to the frenum of the lip. The lateral lobules ( n ) had increased much transversely, and appeared each to lie divided into an anterior and a posterior portion. They were compressed by the true palate, which was folded at this part, as at the tenth week, into wrinkles, the longest and anterior of which stretched across the median line from the right to the left side. The papil he (3 and 4), with their fol- licles, were fully developed. The other two papilla; (1 and 2, Fig. 10) had not undergone much change, but the small bulging (5, Fig. 10) had now become a distinct papilla, and its follicle had begun to show itself. The uvula was well marked. Lower Jem . — The lines of junction of the interfollicular PULPS AND SACS OF THE HUMAN TEETH. 11 septa had almost disappeared, and the mouths of the follicles had become more distinct. The mouths of the three anterior follicles had an an- terior lip, the free edge of which was directed somewhat inwards. It was ne- cessary to lift up this lip with the needle to obtain a view of the contained papilla. At the posterior part of the dental groove, another papilla with a notched lamina, both productions from the external lip, had appeared (5, Fig. 13). Breadth of superior arch 12j lines ; length, 2. 7. 13 tli week . — Upper Jaw . — There was little change in the configuration of the palate since the former week. The lobe running across the median line was still visible. The frenum of the upper lip had become closely attached to, and continuous with, the median lobule. The outlines of the horse-shoe lobe were still perceptible, and on its external side the lobule, all along marked (r), was visible. The outer lip of the dental groove, or the external alveolar process, was equally developed all around. The upper lip was still much retracted. There were ten papillae inclosed in open-mouthed follicles, and ranged at nearly equal distances all around the dental groove* The four anterior papillae were flattened from before back- wards with a straight edge, and were somewhat similar to the future incisive teeth. The next one on each side was a simple cone. The two posterior on each side were also conical, but flattened transversely, so as considerably to resemble carnivorous molars. Each of these papillae ad- hered by its base to the fundus, while its apex, as during the eleventh and twelfth weeks, presented itself at, or, as in the present instance, protruded from, the mouth of its * Arnold, Salzburg Mcd.-Chirurg. Zeitung, 1831, Erster Band, p. 236. Valentin, Handbuch der Entwickelungs-gcschichte des Menschen, p. 482. 12 ON THE ORIGIN AND DEVELOPMENT OF THE follicle. The point of the needle could be introduced through the mouth, so as to move the papilla about in the interior of the follicle. By removing the outer lip of the dental groove, and the outer wall of all the follicles by the scissors, a good view was obtained of the configuration of these parts (Fig. 14). The follicles were observed to be mere duplications of the membrane of the groove, and consequently of the general g astro-intestinal mucous membrane. The inner surface of the follicles was of a greyish-yellow colour. The papillae had increased relatively so as to protrude from the mouths of their follicles. They were granular, friable, and of a dead-white colour. Lower Jaw . — No remarkable change had taken place in the lower jaw, except in the relative enlargement of the papillae, and in the distinct development of the follicle of the posterior papilla (5, Fig. 13). The outer lip of the dental groove was not very distinctly marked, but the inner was well developed. The breadth of the superior arch was 3 lines, and the length was also 3 lines. 8. 14th week . — Upper Jaw . — The median lobule had undergone little change, the lateral lobules had become broader from before backwards, apparently in consequence of the retraction of the palate, which, instead of exhibiting on its anterior part the confused transverse wrinkles formerly mentioned, presented on its lateral divisions (corresponding to the liorse-shoe lobe) four or five parallel rugae, which were apparently remains of the wrinkles. The upper lip had again become full, so that its free edge was on a level with the surface of the palate. The soft outeF edges of the palate and the anterior edges of the lateral lobules were now closely applied to the outer lip of the dental groove, so as to close the PULPS AND SACS OF THE HUMAN TEETH. 13 3 HU a, ffoSs) for a vertebrate animal. The mouth of the entomosomatous animal is invariably situated between two somatomes, so that a certain number of somatomes are interposed between it and the anterior termination of the body. As the mouth is only one of a number of openings situated between somatomes, I find such openings conveniently distinguished as metasomalomic. The mouth of the neuropod is a neural, that of the luema- pod a haemal metasomatomic opening. As the somatome exhibits in its structure corresponding segments of certain or of all the organic systems, I have found the following morphological terms extremely convenient in referring from the segment of one organic system to the cor- responding segments of the others. For the entire framework of an entomosome, whether this framework be developed in its integument or in its interior — whether it be fibrous, cartilaginous, or osseous — I employ the term sclerome (ffzXrifog, with the termination of completeness). To a segment of the sclerome I apply the designation sclero- tome fog, r'lpvu). An aggregate of more or less modified sclerotomes I name a syssclerotome (