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ANATOMICAL AND PHYSIOLOGICAL 
 
 COMMENTARIES. 
 
 BY HERBERT MAYO, 
 
 SURGEOX AND LECTURER IN ANATOMY. 
 
 NUMBER n. JULY, 1823. 
 
 LONDON : 
 
 PRINTED FOR THOMAS AND GEORGE UNDERWOOD, 
 32, FLEET-STREET. 
 
 1823. 
 
V, 
 
 a 
 
 1.OND0N: 
 
 VRTNTICD UY THOMAS DAVISON, WlHTEFliHUlS. 
 
CONTENTS. 
 
 On the Cerebral Nerves, with reference to Sensation 
 and voluntary Motion . . . .1 
 
 On the Structure of Horn, Hoof, and Cuticle . 22 
 On Local Action . . . . . 34 
 
 Remarks in Defence of the Hunterian Theory of 
 Absorption . . . . 42 
 
 Examination of a Body soon after Parturition . 46 
 
 Inquiries respecting the Structure of the human 
 Brain, by Professor Reil . . . .48 
 
 Of the Medulla Oblongata, and the Peduncles of the 
 Cerebellum, by Professor Reil . . .84 
 
 Of the Anterior Commissure, the Septum Lucidum, 
 and the Fornix, by Professor Reil . .11,3 
 
 Supplement to the Anatomy of the Cerebrum and 
 Cerebellum, by Professor Reil . . .119 
 
 Remarks upon the Spinal Chord, and the Nervous 
 System generally . . . .132 
 
 
 XS-778 
 
ANATOMICAL AND PHYSIOLOGICAL 
 
 COMMENTARIES. 
 
 No. II 
 
 On the Cerebral Nerves, vjith reference to Sensation 
 and voluntary Motion, 
 
 If other evidence were wanting, the distribution of 
 the first and second nerve, and of the portio mollis of 
 the seventh, would sufficiently attest their different and 
 exclusive uses as nerves of the special senses ; in like 
 manijer, the distribution of the greater part of the 
 third, of the fourth, and of the sixth nerves to volun- 
 tary muscles *, which receive filaments from no other 
 
 * By voluntary muscles I mean such as during health, 
 and when their use has not been neglected, can be moved 
 at will. At the close of this essay the question is noticed, 
 whether any such muscles habitually act involuntarily. 
 
 B 
 
2 
 
 source, demonstrates that these nerves are voluntary 
 nerves, as well as conducive to muscular sensation. 
 Perhaps it is not unfair to argue analogically from the 
 preceding instances, that the same surface of the brain, 
 or spinal chord, furnishes to each voluntary muscle of 
 the body its voluntary and sentient nerves, if the two are 
 not identical ; a circumstance, which I shall presently 
 mention, attending injuries of the portio dura, and of 
 the motor linguae, corroborates this supposition. 
 
 Where several nerves are so distributed to a part 
 as to afford no certain clue to a knowledge of their 
 separate offices, the division of these nerves singly, in 
 living animals, is well calculated to determine the in- 
 fluence, which belongs to each ; but this method is in- 
 applicable in various instances, owing to the difficulty 
 both of exposing nerves when small and deeply seated, 
 and of appreciating the changes which possibly ensue, 
 when they have been successfully divided. In this 
 uncertainty some assistance may be derived from 
 noticing the effects of mechanically irritating single 
 nerves in living and in dead animals. 
 
 If a nerve, known to be a voluntary nerve, from the 
 paralysis and flaccid state of one or more voluntary 
 muscles, which follows its division in a living animal, be 
 exposed and divided in an animal very recently killed, 
 the muscles, which it supplies, are excited to a single 
 momentary contraction, whenever the extremity of 
 the nerve connected with them is pinched, as with 
 dissecting forceps, care being taken that each successive 
 impression be made on the nerve at a point nearer 
 
3 
 
 to the muscle than the last. If a nerve, known to be- 
 long exclusively to sensation, pass by or through a 
 voluntary muscle, no similar effect follows, when it is 
 similarly injured : thus, the muscles of the lips in an 
 ass are convulsed w’hen the portio dura is mechanically 
 irritated, but remain unaffected when the branches of 
 the fifth, which perforate them, are pinched. Hence 
 it may be inferred, that where the muscles of a part 
 are voluntary, those nerves convey to it the influence 
 of the will, on the injury of which, in the way described, 
 muscular action ensues. 
 
 If the nerves distributed to the heart, to the stomach, 
 and to the intestines, the fibre of which is beyond 
 all doubt an involuntary muscle, be pinched, no im- 
 mediate change follows in the action of these parts. If 
 then it should be found that one or two other irritable 
 parts, which, in human beings in general, the will 
 cannot directly excite to action, be convulsively con- 
 tracted, when nerves attached to them and discon- 
 nected with the brain be pinched, would it be admis- 
 sible to doubt, whether possibly these movements are 
 not instinctive, and thus to place them on a par with 
 the infant’s respiration ? leaving the question still open 
 whether instinct imply or not the agency of the will. 
 
 If a nerve, known to belong to the sense of touch, 
 by the immediate insensibility of the surface, which it 
 supplies, incurred on its division, be divided, and the 
 portion next the brain pinched with the forceps, in a 
 living animal, indications of violent pain are given. 
 Such an injury of the facial branches of the fifth in a 
 
 B 2 
 
4 
 
 living ass is attended with the result mentioned, W’hich 
 however does not ensue, when the portio dura is 
 pinched in that animal. I had conjectured that a 
 general criterion to distinguish nerves of cutaneous or 
 similar sensation might be derived from the preceding 
 remark ; but I have since found, that in animals less 
 patient than the ass, as the cat and dog, the irritation 
 of the portio dura produces an expression of pain di- 
 stinct, though not as violent, as that resulting from an 
 injury of the fifth : this effect, I suppose, depends upon 
 the connexion of the portio dura with muscular sensa- 
 tion. Perhaps, as there is an evident difference in the 
 intensity of pain occurring on the irritation of a cuta- 
 neous and of a muscular nerve, it may still be in- 
 teresting to ascertain in what degree different nerves 
 are sensible, as a means of gaining collateral evidence, 
 however slight, of their uses. 
 
 The first problem of any difficulty furnished by 
 the cerebral nerves is to determine the cause of the 
 movements of the iris. To assist towards its solution 
 thirty pigeons were employed in experiments, of which 
 the following are the results: 
 
 1. When the optic nerves are divided in the cranial 
 cavity of a living pigeon, the pupils become fully 
 dilated, and do not contract on the admission of in- 
 tense light. 
 
 2. When the third nerves are divided in the cranial 
 cavity of a living pigeon, the same result ensues : in 
 both these cases the surface of the eyeball retains its 
 feeling. 
 
5 
 
 3. When the fifth nerve has been divided on one 
 side in the cranial cavity of a living pigeon, the iris on 
 that side contracts as usual on the admission of light, 
 but the surface of the eyeball appears to have lost its 
 
 4. When the optic nerves are pinched in the cranial 
 cavity of a living pigeon, or immediately after its de- 
 capitation, the pupils are contracted for an instant on 
 each injury of the nerves. 
 
 5. When the third nerves are similarly irritated in 
 the living or dead bird, a like result ensues. 
 
 6. When the fifth nerve is similarly irritated in the 
 dead bird, no affection of the pupil is observed. 
 
 7. When the optic nerves have been divided within 
 the cranial cavity of a pigeon immediately after its 
 decapitation, if the portion of the nerves attached to 
 the eyes be pinched, no contraction of the pupil en- 
 sues : if the portion adhering to the brain be pinched, 
 a like contraction of the pupil ensues, as if the optic 
 nerves had not been divided. 
 
 8. The previous division of the fifth nerves in the 
 preceding experiment produces no difference in the 
 result. 
 
 9. When the third nerves have been divided in the 
 cranial cavity of the living or dead bird, no change in 
 the pupil ensues on irritating the entire or divided 
 optic nerves. 
 
 It may be inferred from the preceding induction, 
 that diminution of the pupil results from the action, 
 and dilatation of the pupil from relaxation of the iris; 
 
6 
 
 that the nerve which immediately controls the action 
 of the iris is the third nerve ; that in the habitual va- 
 riations of the pupil, an impression is conveyed to the 
 brain along the optic nerve, which is followed by an 
 affection of the third pair, causing the pupil to con- 
 tract or to dilate ; finally, that the common feeling of 
 the eye is derived from the fifth nerve. 
 
 Among the preceding experiments, those, which 
 were performed upon the separated head, succeeded 
 only, when the nerves were very quickly exposed, 
 and the removal of the bone and upper surface of the 
 brain executed separately, and without violence. 
 
 It is a curious circumstance, and one not generally 
 known, that the pupil is contracted during sleep to a 
 smaller circle than when submitted to the same light 
 at other times. This remark I made and verified in 
 several instances some years ago. My friend, Mr. 
 Caesar Hawkins, to whose assistance I am much in- 
 debted in the performance of the preceding experi- 
 ments, recently, at my request, repeated this observa- 
 tion ; and communicated to me an additional fact, that 
 the pupil, thus habitually diminished during sleep, is 
 capable of still further contraction on the admission 
 of intense light. In most cases, when the upper eyelid 
 of a person in sound sleep is raised, the eye is found 
 directed straight forwards : but in some instances, the 
 eye is directed upward and outward, I suppose, to 
 avoid the light. At the moment of waking, the pupil 
 broadly dilates, and then, after two or three irregular 
 contractions, or at once, resumes its usual tone. 
 
7 
 
 The peculiarity, which consists in the derivation of 
 the three muscular nerves of the eye from distinct 
 parts of the brain, is not easily explained. Four 
 muscles retract the eyeball, and in various combina- 
 tion may direct its axis upward, downward, outward, 
 or inward : two muscles carry the eye forward, and 
 neutrahze the further effect each of the other : but one 
 nerve, the third, supplies three of the first set (not to 
 mention the levator palpebrae), and one of the second. 
 Again, the sixth supplies the abductor ; but the action 
 of that muscle, in human vision, has nothing pe- 
 culiar : it may have, doubtless, in animals, both eyes 
 of which cannot be directed at once to objects placed 
 in a certain relation to the head ; and it is possible 
 that, for a similar reason, the obliquus superior oculi, 
 which directs the axis of the eye downward and out- 
 ward, may be supplied exclusively by the fourth. 
 
 The influence of the remaining parts of the fifth I 
 have ascertained by experiments made upon asses, or 
 have inferred from the exclusiveness of their distribu- 
 tion to particular parts. The course of the fifth in hu- 
 man beings corresponds so accurately with that in the 
 ass, that I venture to suppose the use of each part of 
 the nerve the same in both instances. The fifth nerve 
 supplies the skin upon the forehead, upon the cheek, 
 and upon the chin, the mucous membrane of the 
 nose and fauces, and the tongue and salivary glands. 
 In the last paper of the preceding number I mentioned 
 that the division of the supraorbital, infraorbital, and 
 inferior maxillary nerves, at the points, where they 
 
8 
 
 emerge from their canals upon the face, produces loss 
 of sensation, and of that alone, in the corresponding 
 parts of the face. I have since, after the division of 
 the fourth branch, which emerges'on the face, namely, 
 that which joins the portio dura, ascertained that this 
 branch likewise is a nerve of sensation, inasmuch as 
 the cheek loses sensation upon its division. 1 men- 
 tioned in addition, that I concluded that other 
 branches of the fifth nerve, from their distribution 
 to the pterygoid, masseter, temporal, and buccinator 
 muscles, are voluntai'y nerves. This conclusion in- 
 volved a trifling error : the pterygoid, masseter, and 
 temporal muscles are indeed exclusively supplied by 
 the fifth, and, therefore, without doubt the branches 
 so distributed ai'e voluntary nerves; but the buccinator 
 receives branches from the portio dura as well, and I 
 have found, subsequently,'-that pinching the branch of 
 the fifth, which perforates that muscle, produces no 
 action in it. I should remark, on the other hand, 
 that the fifth exclusively supplies a fifth muscle, the 
 circumflexus palati ; whence it may be inferred that 
 the fifth is the voluntary nerve of that muscle as well 
 as of the four great muscles of mastication. 
 
 Now, it is well known to anatomists, that the fifth 
 nerve at its origin consists of two portions ; a larger 
 part, which alone enters the Gasserian ganglion ; and 
 another smaller, rising from the annular protuberance 
 before the former, which subsequently does not enter 
 but passes below the ganglion to join itself with the 
 third division of the fifth, and escape with it through 
 
9 
 
 the foramen ovale. Towards the close of last summer 
 I endeavoured to trace the final distribution of this 
 small portion in the ass, and succeeded in making out 
 that it furnishes those branches, which are distributed 
 exclusively to muscles: this dissection I have repeated 
 four times, and in an adjoined drawing have repre- 
 sented the fact as existing in the ass. I have since 
 ascertained that in the human body precisely the same 
 distribution exists. But the remaining branches of the 
 fifth are proved to be nerves of sensation. Thus it ap- 
 pears that the fifth nerve consists of two portions, one 
 of which has no ganglion, ajid is a nerve of voluntary 
 motion (and probably of muscular sensation), and an- 
 other, which passes through a ganglion, and furnishes 
 branches, which are exclusively nerves of the special 
 senses. Soemmering, in his very excellent treatise on 
 anatomy, which I believe is universally received as the 
 best extant, compares the fifth pair of nerves with the 
 spinal nerves * : by this analogy I was led , to con- 
 jecture that the double roots of the spinal nerves have 
 
 * Minor nervi (quinti) pars eandem fere latitudinem 
 servat, et exceptis nonnullis exterioribus fibris, plexura 
 intrantibus, majorem portionem descendendo oblique prae- 
 terit, neque ei fibras addit (eum fere in modum, quo 'prior 
 radix nervorum spince medullae ganglion non intrat), fibras 
 tamen proprias multls modis inter se invicem commiscet. 
 
 S. R. Soemmering de corporis humani fabrica (Trajecti 
 ad Maenum, 1798.) Vol. IV. p. 214. 
 
10 
 
 functions corresponding with those of the fifth, and 
 that the large posterior portion of each spinal nerve, 
 with its ganglion, belongs to cutaneous sensation, and 
 the anterior branch to voluntary motion. When I 
 was engaged in experiments to determine the fact, 
 M. Majendie’s were published, which establish the 
 justness of my conjectui’e. 
 
 In the preceding number I have mentioned that the 
 division of the portio dura of the seventh nerve pa- 
 ralyzes the muscles of the face. Now the buccinator 
 muscle is intermediate between the cutaneous muscles 
 of the lips and nostrils, and the powerful muscles 
 moving the jaw ; and it is somewhat difficult to de- 
 termine, after the division of the portio dura, whether 
 the muscle in question be paralyzed or not : but the 
 question may be decided by pinching in succession on 
 the dead ass that branch of the fifth which perforates 
 [he buccinator, and then the trunk of the portio dura. 
 While the former experiment is unattended with any 
 effect, the latter produces a distinct spasm of the buc- 
 cinator, as well as of the other muscles about the lips 
 and nostrils. If the portio dura be pinched with the 
 forceps in a living ass, no expression of pain follows ; 
 if in the cat, the expression of pain is distinct. 
 
 The tongue is supplied on either side with three 
 nerves ; the gustatory, the ninth, and the glosso-pha- 
 ryngeal nerve. 
 
 On dividing the gustatory nerve on either side, in 
 a rabbit, the sensibility of the surface of the tongue 
 appeared to be lost ; but the muscles of the tongue 
 
11 
 
 did not appear to be paralyzed. On pinching the 
 gustatory nerves in several animals, immediately after 
 their death, no spasm whatever occurred in the muscles 
 of the tongue. On pinching the same nerves in living 
 rabbits, pain was evinced. 
 
 In the preceding number, I mentioned that the 
 tongue of a rabbit appeared paralyzed by the division 
 of the ninth pair of nerves. I have since made other 
 experiments, with a similar result. I divided the ninth 
 nerve on one side of the tongue in a dog : the animal 
 did not seem much incommoded, but lapped up milk 
 readily. I then divided the nerve on the opposite 
 side the animal appeared distressed, and did not 
 again lap up the milk offered to it, though it smelt to 
 it ; and finally, when mustard was smeared upon its 
 nostrils, it made no use of its tongue to remove it, 
 though evidently suffering from it. On exposing the 
 ninth nerve, after its division, in an animal recently 
 killed, and pinching the part attached to the tongue, 
 the muscles of the tongue are convulsed. When the 
 ninth nerve is pinched, in a living dog or cat, an ex- 
 pression of pain follows. 
 
 I am inclined to suppose, on coupling the last- 
 narrated fact with what has been said respecting the 
 use of the other portions of the fifth, that the gustatory 
 nerve is not a nerve of taste alone, but of touch like- 
 wise, as far as the surface of the tongue possesses this 
 mode of sensibility ; and entertain no doubt that the 
 ninth nerve is rightly called the motor lingute. 
 
 When the glosso-pharyngeal nerve is pinched in 
 
\2 
 
 an ass recently killed, a distinct, convulsive action 
 ensues, appai’ently including and limited to the stylo- 
 pharyngeus muscle and the muscular fibres about the 
 upper part of the pharynx. Thus the glosso-pharyn- 
 geal is in part, probably, a nerve of voluntary mo- 
 tion ; and it may be inferred that it is a nerve of 
 sensation, though not of taste, from its distribution to 
 the surface at the root of the tongue. 
 
 I am enabled, through the politeness of Dr. Mac- 
 michael, to substantiate the preceding conclusions re- 
 specting the use of the nerves of the tongue, by the 
 detail of some of the particulars of a case occurring 
 under his care in the Middlesex Hospital, which I 
 have recently had an opportunity of witnessing. 
 
 A young man, twenty-six years of age, of singularly 
 dissolute habits, was seized with paralysis of the left 
 side of the face, on the 13th of October, 1822 : in little 
 more than a fortnight he became deaf of the left ear; 
 and about the same time lost, but not suddenly, sensa- 
 tion in the left side of the face. When first seized, he 
 remarked, that he could not close the left eyelids, un- 
 less he at the same time closed the right : subsequently 
 he has lost the power of raising the left eyelid, and of 
 moving the left eyeball, which is not sensible when 
 touched ; the pupil does not change, when a strong 
 light is presented to the eye : the eye is now much 
 inflamed, and the cornea superficially ulcerated ; but 
 before this occurred, which was towards the middle 
 of April, the sight of the left eye became dim ; at 
 present he can only faintly distinguish with it the 
 
13 
 
 brightest light ; finally, he has lost the sense of smelling 
 in the right nostril. 
 
 The cause of these symptoms may or may not be 
 disease of the cranial bones, or of the dura mater, 
 affecting several of the cerebral nerves at their exit 
 through the cranium; but, certainly, the olfactory 
 nerve, on the left side, has lost its function ; and that 
 of the optic, on the same side, seems impaired. The 
 third, the fourth, and sixth nerves, again, are distinctly 
 paralyzed, inasmuch as the eye is immoveable, and 
 the eyelid cannot be raised. The portio dura is pa- 
 ralyzed ; for the mouth is drawn towards the opposite 
 side, and the features are immoveable on the left side, 
 and the eyelids cannot be pressed together. The 
 muscular branches of the fifth are likewise paralyzed ; 
 for if this person place a crust of bread between his 
 teeth, and bite it forcibly, the masseter on the right 
 side becomes hard, but that on the left remains 
 flaccid. Again, the branches of the fifth, which supply 
 the skin of the face, have lost their functions ; since 
 the surfaces, which these supply, are insensible : but 
 the ear, the skin over the parotid, and a narrov/ sur- 
 face extending to the upper lip, in the line of the 
 facial artery, being parts supplied by the second 
 cervical nerve, as well as the back and upper part of 
 the head, are not so ; and it is curious to observe, that 
 sensation on the fore part of the face extends a little 
 beyond the median plane upon the left side. Further, 
 the mucous surfaces of the eye, of the left nostril, and 
 of the gums on the left side, are insensible to touch: 
 
14 
 
 and the tongue, on the left side, when its surface alone 
 is irritated, is insensible to touch as well as to taste. 
 
 Th us there exists complete evidence, that the func- 
 tion of the fifth nerve is in this case suspended : but 
 if the patient be directed, when his mouth is open, to 
 raise the tip of the tongue to the roof of the mouth, 
 the fraenum linguae remains in the median plane of 
 the body : it may thence be inferi'ed, that the ninth 
 nerve is unaffected; and therefore, that the loss of 
 sensation of both kinds, on its surface, results from 
 an affection of the fifth. Yet, when the substance of 
 the tongue on the left side is pinched, a dull sensation 
 of pain arises there. Is it not probable, that this is 
 a muscular sensation, conveyed along the ninth nerve, 
 consistently with what I have remarked respecting its 
 injury in living animals? But I have adduced this 
 case, principally, to illustrate the function of those 
 branches of the glosso-pharyngeal nerve, which are 
 distributed to the papillae conicas and the surface near 
 the root of the tongue. In this individual, the sur- 
 face at the root of the tongue upon the left side is 
 indeed insensible to touch or taste : sugar placed upon 
 either side is not tasted ; but Caytene pepper placed 
 on either produces, after a time, a sensation of heat, 
 though no perception of its peculiar savour : a probe 
 applied to either side, again produces the feeling of 
 nausea, and an effort of retching. May it not be 
 presumed, that these phenomena result from the ex- 
 clusive agency of the glosso-pharyngeal nerves? 
 
 In this person, the paralyzed side of the face is 
 
15 
 
 slightly oedematous: when his countenance became 
 suffused on touching the root of the tongue with a 
 probe, the suffusion was equal on either side, if not 
 rather greater on the left. 
 
 The spinal accessory nerve is extremely singular in 
 its circuitous course, and in its origin, from the side 
 of the spinal chord, behind the ligamenta denticulata : 
 when this division of the eighth nerve is irritated in a 
 living cat or dog, the animal expresses considerable 
 pain, and the muscles which the nerve supplies are 
 convulsed, when the experiment is repeated, after the 
 division of the nerve, on the part adhering to them. 
 
 The nervus vagus, from the obvious distribution of 
 its branches to the membrane of the larynx, and its 
 copious ramification on the oesophagus, may be sup- 
 posed to belong, in part, to sensation. Asses, cats, 
 and dogs, almost invariably express great pain when 
 this nerve, yet entire, is pinched with the forceps; 
 and after its division equal suffering appears to result 
 from pinching the part connected with the brain. 
 M. Majendie’s experiments have proved that the 
 nervus vagus furnishes voluntary branches to the 
 muscles of the larynx. If the nerve, yet entire, be 
 pinched with the forceps, in an animal alive or re- 
 cently killed, or if, after division, its lower part be 
 thus irritated, the oesophagus is convulsively shortened 
 at each repetition of the injury. It may be remarked, 
 that pinching a nerve virtually destroys its connexion 
 with the brain ; and thus in the present instance, after 
 
16 
 
 the texture of the nervus vagus has been bruised, to 
 produce sensation a point nearer the brain than that 
 last-injured must be irritated ; to produce a spasm in 
 the CESophagus, again, a point more remote from it. 
 No apparent movement in the stomach attends this 
 spasm of the oesophagus. 
 
 The sympathetic nerves are formed of branches 
 from the sentient part of the fifth, and from the sixth 
 nerves, and are continually reinforced by branches of 
 the spinal nerves, derived, as Scarpa has ascertained, 
 equally from their anterior and posterior roots. Scarpa 
 has further determined, that ganglia are but fine plex- 
 uses, and that no nervous filaments arise or terminate 
 in the gray matter, \vhich is contained in these sub- 
 stances, intended, perhaps, for the security alone of 
 their fine organization. Hence it follows, that the 
 sympathetic nerves, in human beings, can only be 
 regarded as branches of the cerebral and spinal 
 nerves, destined for particular uses ; one of which is 
 illustrated by the cessation or interruption of the 
 heart’s action, which occurs in a recently decapitated 
 animal, when the spinal chord is crushed. No doubt, 
 in this case, the impression is transmitted from the 
 spinal chord to the heart, through the sympathetic 
 nerves. These nerves, on the other hand, have no- 
 thing to do with voluntary motion; but it is probable 
 that they are concerned in sensation, though no ex- 
 pression of pain follows their mechanical injury in the 
 neck or abdomen of the ass, the cat, or the dog. 
 
17 
 
 It may not be out of place to subjoin a few remarks 
 upon the various ways, in which nerves contribute to 
 the action of different irritable parts. 
 
 The leading distinction in irritable parts is, that 
 some, on their removal from the body, continue for 
 a period alternately to contract and dilate; while 
 others, with the exception of the mere quivering of 
 the flesh, remain passive, and require the application 
 of a mechanical or chemical stimulus to their sub- 
 stance, or to the nerve connected with them, in order 
 that a single brief contraction may ensue. In a paper 
 in the former number of this work, I mentioned va- 
 rious facts, which tend to prove that one of the parts 
 of the fii’st class, namely the heart, contains within 
 itself its principle of action, and undergoes spon- 
 taneous and alternate contractions and dilatations, as 
 a result of its structure. 
 
 Of the second class of parts, some, as the muscles 
 of the trunk, of the limbs, and the like, are distinctly 
 influenced by the will; in others, again, as the mus- 
 cles of the chest, and of the face in the expression 
 of emotion, the influence of the will is not consciously 
 employed, under ordinary circumstances, to produce 
 their action; and a question arises, v.liether this or 
 some other principle stimulate the nni cles on these 
 occasions. Much may be advanced on either side. 
 On the one hand, it is clear that an influence, inde- 
 pendent of the will, occasionally throws voluntary 
 muscles into action, as appears in tetanus and other 
 spasmodic disorders ; and is shown remarkably in the 
 
 c 
 
18 
 
 physiological experiment of instating the skin on the 
 lower extremities, after the division of the spinal chord 
 in the back, when the occurrence of action limited to 
 the muscles of the inferior extremities, evinces that a 
 connection exists, independently of the will, between 
 sentient surfaces and the action of voluntary muscles. 
 I have varied this experiment by dividing the spinal 
 chord at once in the neck and in the back, upon which 
 three unconnected nervous centres exist ; and the di- 
 vision of the skin in either part (and especially at the 
 soles of the feet, in the two hinder portions) produces 
 a convulsive action of the muscles in that part alone. 
 The same influence may, then, possibly regulate the 
 unconscious actions, to which these remarks relate. 
 On the other hand, it may be urged, that in many 
 actions purely voluntary, which have become habitual, 
 it is difficult to trace the influence of the will ; that the 
 actions in question are now habitual, and began as 
 instinctive but voluntary actions; and that, in con- 
 firmation of this view, the muscles of the trunk and 
 limbs occasionally act as muscles of expression ; and 
 again, that the action of the diaphragm in breathing, 
 and of the muscles of the face in expression, may be 
 refrained from by a resolute effort of attention, or 
 produced by a conscious exertion of the will ; finally, 
 that the existence of but one nerve for the actions of 
 each of these muscles, (which are sometimes at least, 
 and can at any time be influenced by the will), is a 
 little, though very little, in favour of their being al- 
 ways excited to their habitual action by this stimulus; 
 
19 
 
 and that the physiological experiment of making se- 
 parate nervous centres, by division of the spinal mar- 
 row, admits of explanation on supposing the principle 
 of volition to continue for a short period extended to 
 the portions separated from the brain; a conjecture 
 consistent with, perhaps, but far from established by 
 the very curious fact, that the convulsive movement 
 of the leg of an animal thus circumstanced, when the 
 sole of its foot is irritated, is accurately the gesture 
 which the animal employs, when, in undisputed pos- 
 session of sensation, it retracts its limb from a similar 
 aggression, and not to appearance, at least, a mere 
 convulsive throe. 
 
 These reflections, on either part plausible, leave 
 the question undecided, whether any muscular actions 
 exist, during health, directly produced by an im- 
 pression derived along the nerves, which is not a 
 conscious or unobserved exercise of the will ; but, 
 setting that question aside, I think it may fairly be 
 inferred, from all the facts above narrated, that the 
 third, fourth, sixth, seventh, and ninth nerves, to- 
 gether with a portion of the fifth, not included in its 
 ganglion, are nerves in every respect corresponding 
 with those formed by the anterior roots of the spinal 
 nerves ; and that they have the same relation to the 
 first and second nerves, to the auditory nerves, and 
 to the portion of the fifth included in either Gasserian 
 ganglion, which the anterior roots of the spinal nerves 
 have to the fasciculi rising on the back part of the 
 spinal chord. It is not easy to arrange the nerves of 
 
 c 2 
 
20 
 
 the eighth pair in the same system : but, on the whole, 
 these seem to partake of the nature of both kinds of 
 nerves indicated above. The nervus vagus has a gan- 
 glion, and is distinctly a nerve of sensation and volun- 
 tary motion. The glosso-pharyngeal nerve has a gan- 
 glion, and is again, it would appear, a nerve of sensa- 
 tion, and at least of instinctive motion. Finally, the 
 spinal accessory may, possibly, involve both these pro- 
 perties, though it has no ganglion, with which I am 
 acquainted. It is true that this statement does not 
 satisfactorily account for the anatomical peculiarities 
 of these nerves ; and, doubtless, much remains to be 
 discovered respecting their influence, even on sensa- 
 tion and muscular motion. 
 
 Explanation of part of the Fifteenth Plate. 
 
 Fig. I. 
 
 Represents the fifth nerve of an ass, removed from 
 the cranium : it is reversed, and the investing mem- 
 brane dissected off. 
 
 1. The larger portion of the fifth nerve. 
 
 2. The smaller portion. 
 
 3. The Gasserian ganglion, which the former en- 
 ters, while the latter passes below it. 
 
 4. The first, or ophthalmic division of the fifth. 
 
 5. The second, or superior maxillary division. 
 
 6. The gustatory, and inferior maxillary branches, 
 
21 
 
 which, with the portion 2, and the branch 7 dis- 
 tributed through the buccinator to the mucous sur- 
 face of the fauces, constitute the third division of the 
 fifth. 
 
 8, 9, 10. Distribution of the smaller portion 2 into 
 three branches, to the temporal and masseter, to the 
 circumflexus palati, and to the two pterygoid muscles. 
 
 A few fine filaments, of which one alone is here 
 exposed, and represented larger than it should have 
 been, are reciprocally interchanged between the mus- 
 cular portion of the fifth, and the sentient portion 
 beyond the ganglion. 
 
 All parts of the fifth nerve, in the ass, are more or 
 less reticular, in the arrangement of their fibres, near 
 their origin, and for the greater part of their course. 
 Towards their fi,nal distribution the fibres are distinct, 
 and rarely interlace with one another. 
 
 In justice to M. Fleurens, I should mention that 
 my experiments respecting the movements of the iris 
 were suggested by reading the account (contained in 
 M. Majendie’s Journal, Vol. II. Number 4.) of his 
 very interesting reseai’ches ; and, in justice to myself, 
 that the statements of M. Fleurens, at all relative to 
 the iris, are the following alone : that, on pricking the 
 tubercles or optic nerves, the pupils contract; that the 
 iris preserves its mobility after the removal of the lobe 
 cerebral of the opposite side, and again after that of 
 the tubercles; and is only paralyzed after the pro- 
 found extirpation of the tubercles or section of the 
 optic nerve. 
 
22 
 
 On the Structure of Horn^ Hoof and Cuticle. 
 
 The horn of the rhinoceros is described by Dr. 
 Macartney as “ made up of a number of fibres 
 resembling strong hairs consolidated together, and 
 rendered smooth upon the surface, except around 
 the base, where the external fibres being broken 
 off present the appearance of a brush * but it 
 is not I believe generally supposed that the horn of 
 the common ox is formed in a very similar manner. 
 My friend, Mr. Bremner, communicated this ob- 
 servation to me, which he had ascertained by various 
 methods. 
 
 If a longitudinal section be made of an adult 
 horn, it is found to be solid near its point, but after- 
 wards to inclose a conical cavity, which is widest at 
 the base of the horn. From the closed extremity of 
 this cavity the substance of the horn becomes gra- 
 dually though not uniformly thinner, till, at the base, 
 it blends insensibly with the cuticle. Of the substances 
 contained in this cavity, the external is a delicate mem- 
 brane, which varies in colour with the different shades 
 of the horn, and clothes a tough prolongation of the 
 cutis vera ; the latter is supported on a central bony 
 process. 
 
 * Rees’s Cyclopsedia. Article Horn. 
 
23 
 
 On examining the cut surfaces of the horn (of which 
 a variegated specimen should have been selected), the 
 middle of the solid part has the appearance of being 
 composed of fibres, extending nearly vertically from 
 the tip of the bony process, or rather of the membrane 
 covering it, to the tip of the horn ; the lateral part 
 again appears to be composed of fibres arising every 
 where from the lateral surface of the secreting mem- 
 brane, and running forwards at a very acute angle. 
 Every fibre does not indeed appear to be throughout 
 of the same colour, so that the general clouding of the 
 horn does not prove the structure to be what is here 
 described; but, on observing the surfaces resulting 
 from many sections, it is difficult not to adopt this 
 supposition. 
 
 Further, it is easy, where some violence has been 
 used in rending away portions of fresh horn imper- 
 fectly separated by the saw, to raise long fibrils in di- 
 rections consistent with the preceding account : but 
 what is most to the purpose is, that if the horn be 
 steeped in liquor potassae for twenty-four hours, and 
 the outer surface, which has become gelatinous, be 
 scraped away, the next part, being only softened by , 
 the alkaline solution, peels readily into fibres, which 
 have the direction above described. 
 
 The hoofs of animals are described as fibrous; but 
 1 have found their structure to vary materially from 
 the simply fibrous structure of horn. 
 
 The several parts of the hoof, in the horse and ass, 
 viz. the frog, the sole, the crust, are all formed alike. 
 
though they differ in solidity. The frog and the sole 
 seem composed of blackish fibres nearly vertical to the 
 vascular surface from which they grow ; but the crust, 
 the firmest part of all, seems to be composed of alter- 
 nate white and black fibres, which rise from the coronary 
 ligament, and descend at an acute angle to enclose the 
 former parts, cohering Avith the lateral and vascular sur- 
 face of the foot by means of peculiar processes termed 
 elastic laminae. 
 
 If a section be made through an hoof, as in fig. 3, 
 [plate XV. the foot represented is that of an ass’s foal] 
 the dark colour and hard consistence of the different 
 parts is found to begin abruptly at a well defined line; 
 above this a narrow whitish layer is found, bounded by 
 a fine black line, the former about 1-lOth of an inch in 
 depth. If the surface of this vertical section be minutely 
 examined, especially with a magnifying glass, it may 
 be seen that the cutaneous surface terminates, or that 
 the horny material begins, at the thin black line I have 
 described. This line again is continually interrupted : 
 long and delicate vascular processes pass through the 
 interruptions into the stratum of softer white matter, 
 the texture of which resembles the opaque substance in 
 a feather : if a transverse slice be taken of this white 
 substance, it is seen to be perforated by innumerable 
 foramina, which transmit vascular processes from the 
 cutis vera. These vascular processes are continued 
 downward, and pass into the firm substance of the 
 crust, and into that of the sole and frog, x’eaching ap- 
 parently half the depth at lea^t of these several sub- 
 
25 
 
 stances, and I am inclined to think very nearly to their 
 under surface. On making an horizontal section of 
 the crust, it is seen that the only white matter in it is a 
 thin cylinder, which immediately surrounds each vas- 
 cular process ; thus the substance of hoof is ratlier a 
 tubular than a fibrous mass. 
 
 The elastic laminae are plates of horny matter, which 
 grow fi'om the under part of the coronary ligament, 
 being continuous with the internal surface of the crust. 
 Each elastic lamina is received between, and, in the 
 recent state, adheres to two vascular laminae, which 
 are processes from the cutis vera covering the foot 
 laterally ; the elastic lamina are carried down with the 
 growth of the crust ; the vascular laminm at their ter- 
 mination are apparently prolonged for a short space 
 in slender villi, and secrete a horny material, which 
 fills up their interstices, so that eventually a solid layer 
 is formed connecting the extremity of the crust to the 
 horny sole : the sides of the elastic laminae are finely 
 fluted. 
 
 The human cuticle, except in the palms of the 
 hands, and soles of the feet, is apparently membrani- 
 form : the cuticle of the elephant even has a similar 
 appearance; yet the structure, which this substance 
 assumes, where it occurs of greater thickness, brings 
 it rather to the nature of horn and hoof, with which 
 it imperceptibly blends. The cuticle of the gizzard of 
 an ostrich resembles the former. The drawing Fiff. 2. 
 [Plate XV.] is from a specimen in my collection, in 
 which the cuticle is distinctly formed of fibres easily 
 
26 
 
 separable from each other, and rising vertically from 
 the secreting surface. Thickened cuticle, from the 
 palm of the hand, hardened in alum and weak spirit, 
 I have found tear in a manner not inconsistent with 
 the supposition that its structure is similar; and in the 
 magnificent treasure of the Hunterian museum Mr. Clift 
 recently pointed out to me specimens of exceedingly 
 thick human cuticle, where the appearance more strik- 
 ingly corresponds with that in the ostrich’s gizzard. 
 
 As instances of the formation of cuticle in a manner 
 similar to that of hoof, I may mention that a soft sub- 
 stance 5 (Fig. 3. Plate XV.), continuous at the back 
 part with the frog, descends around the crust of the 
 horse’s hoof for the purpose of protecting its outer sur- 
 face when newly formed: now this substance blends with 
 the cuticle, is very similar in appearance to the cuticle, 
 yet, for some extent, distinctly receives vascular pro- 
 cesses like the hoof itself. In the Hunterian museum 
 again, there are specimens of the cuticle of the porpesse, 
 and of the narwhal, the structure of which, at first ap- 
 parently fibrous, on minute inspection clearly contains 
 vascular processes like those existing in the horse’s hoof. 
 In the thick human cuticle in the Hunterian museum 
 there is an outer layer less distinctly fibrous; and in the 
 skin of the porpesse and narwhal there is an outer layer 
 seemingly membraniform. It is to be presumed that 
 this alteration in the texture of the part is a sponta- 
 neous change favoured by the action of pressure and 
 of the media, with which the part is in contact ante- 
 cedently to its separation. 
 
27 
 
 The human nail resembles in appearance a thin 
 slice of horn, and in a similar way tears more readily 
 transversely than longitudinally ; yet it is probable, 
 though I cannot say that I have seen any thing like 
 this, that it is composed of longitudinal fibres : in 
 other points nail resembles hoof very closely. Its 
 internal surface has elastic laminae, which are received 
 between vascular laminae of the skin ; and if a longitu- 
 dinal section be made of the end of a finger, it may be 
 seen that the nail has early acquired its fiill thickness, 
 apparently where its colour changes ; and, again, that 
 its tender substance, when newly formed, is protected 
 by a distinct cuticular growth secreted from that fold 
 of skin which overlaps its root : where this cuticular 
 growth is not artificially removed, it rises with the nail, 
 and sometimes may be peeled from its convex surface 
 in as many as three distinct layers. 
 
 Fig. II. Plate XV. 
 
 Represents a section of the gizzard of an ostrich. 
 
 1. Muscular and tendinous substance. 
 
 2. Layer of substance strictly analogous to the cutis 
 vera of the integuments, or more loosely to the tunica 
 nervea and villous coat of the human stomach taken 
 jointly. 
 
 3. Layer of cuticle raised from the last, consisting 
 of fibres vertical to its surface. 
 
28 
 
 Fig. III. 
 
 Section of an hoof, taken from an ass’s foal. 
 
 1. The crust, seemingly consisting of white and 
 black fibres, passing downwards at an acute angle 
 with the coronary ligament 7. 
 
 2. 2. The sole and frog, seemingly composed of black 
 fibres, passing downwards not exactly at a right angle 
 with the secreting surface. 
 
 In both the preceding parts vascular processes are 
 found passing downwards in the same direction with, 
 and between the seeming fibres. 
 
 3. A layer of horny substance, of closer grain and 
 lighter colour, and seemingly less fibrous than the 
 preceding parts: it is a prolongation of the elastic 
 laminae, one of which is represented at 4. 
 
 5. Layer of cuticular substance, overlapping the 
 crust, and continuous at the back part of the hoof with 
 the frog. 
 
 6.6. The narrow, soft, and white layer,found equally 
 between the solid parts of the crust, of the sole, and of 
 the fi’Og, and the surface of the cutis vera, or its pro- 
 longation, on which these substances rest. 
 
 7. The coronary ligament. 
 
29 
 
 Fitt. IV. 
 
 A magnified section of the narrow white layer, 
 mai’ked 5 in Fig. IIL, made in the direction of the 
 vascular processes which perforate it. 
 
 a. The cut extremities of the vascular processes 
 where they enter the solid crust. 
 
 h. The abrupt commencement of the black sub- 
 stance of the crust. 
 
 Fig. V. 
 
 A magnified transverse section of the white layer 
 interposed between the crust and the coronary liga- 
 ment ; it is seen to be perforated by numerous fora- 
 mina of different sizes, which are sections of the cylin- 
 drical canals containing the vascular processes. 
 
 \ 
 
 Fig. VI. 
 
 A highly magnified and somewhat oblique section 
 of the crust. The black ground is the uniform black 
 matter of the crust. The white oval rings are oblique 
 sections of the circular cylinders of white matter, which 
 contain the vascular processes. 
 
 It is difficult to determine the origin of this hard 
 
so 
 
 black substance in the crust; for the vascular processes 
 are every where in that substance contained in white 
 horny substance, as the present figure represents. The 
 black matter begins at once abruptly, and, at the same 
 line, the solid texture of the hoof seems completed, 
 the white substance surrounding the vascular processes 
 being now seemingly firmer than above. 
 
 A rete mucosum exists every where along the sur- 
 face, from which the vascular processes arise, but is 
 wanting at the upper margin of the elastic laminae. 
 The drawings illustrative of the structure of hoof, with 
 the exception of Fig. III. and VII., are taken from 
 the horse. 
 
 Fig. VII. 
 
 A portion removed by sections nearly vertical from 
 the fore part of the crust in the hoof of an ass’s foal. 
 Of this portion the lower part again has been removed 
 by a very oblique section, so as to expose in two views 
 the elastic laminae. Above, the side of one elastic 
 lamina is seen ; below, the obliquely divided edges of 
 several are seen ; and lower down, where these ter- 
 minate in solid horn, corresponding with the portion 3, 
 in Fig. III., an oblique section still shows a faint ap- 
 pearance of the original disposition in plates nearly 
 parallel. 
 
31 
 
 Fig. VIII. 
 
 A magnified transverse section of the elastic laminae 
 in the recent state. They are continuous with the 
 inner surface of the crust, which in the drawing is left 
 unshaded. Their lateral surfaces are delicately fluted. 
 Between each pair a very soft and adherent vascular 
 process intervenes, continuous above with the coro- 
 nary ligament, and laterally with the cutaneous sur- 
 face covering the coffin bone, to which surface, in 
 the recent state, the internal extremity of each elastic 
 lamina is adherent. When putrefaction commences, 
 the hoof is separable from the cutis vera ; the vascular 
 laminae remain with the latter; the elastic laminae 
 separate as part of the former. 
 
 Where the elastic laminae terminate in the sub- 
 stance 3, Fig. Ill, the vascular laminae appear to 
 bi’eak into fine processes, so that the structure of this 
 part, though finer and closer, is yet similar in essential 
 points to that of the crust. 
 
 I have added, in figures IX, X, and XI, drawings 
 of parts of a similar class with the preceding, the struc- 
 ture of which is known. 
 
 Fig. IX. 
 
 Represents a nearly vertical section of the bulb of the 
 whisker of a lioness : in it are shown, 1 st. The firm 
 
32 
 
 and almost cartilaginous oval capsule, in which the 
 root of the hair is inclosed, which is pei'forated above 
 for the escape of the shaft of the hair, and below for the 
 entrance of blood-vessels with a branch of the fifth 
 nerve. 2ndly, The spongy and somewhat vascular sub- 
 stance, which intervenes between the capsule and the 
 hair, and has a remarkable circular canal near its 
 middle, and an inner surface continuous with the 
 cuticle ; and, 3dly, The hair itself, above solid, but its 
 interior of softer matter than its crust ; below, conically 
 excavated, and containing a highly vascular conical 
 pulp. 
 
 Fig. X. 
 
 Represents an oblique section of the bulb of a porcu- 
 pine’s quill. 
 
 Fig. XI. 
 
 Represents a transverse section of another. The 
 thick exterior crust is continued inwards in slender 
 septa, which tend towards the axis of the quill, and in- 
 tervene between the masses of soft white opaque ma- 
 terial contained within. In the hollow extremity of 
 the quill, a nearly spherical and highly vascular pulp 
 is contained, to which a branch of a nerve may be di- 
 stinctly traced. From this pulp vascular processes are 
 derived, which extend in the lines of the septa. The 
 crust is soft at first, and appears wholly formed from 
 
33 
 
 the lower margin of the pulp. A membrane con- 
 tinuous with the cuticle, and apparently not vascular, 
 is every where in contact with the quill, where con- 
 tained in its oblique channel through the skin. This 
 inner membrane terminates at once abruptly at the 
 margin of the crust of the quill: immediately without 
 it a highly vascular membrane exists, which is con- 
 tinuous with the margin of the pulp below, and with 
 the surface of the cutis vera above. 
 
 In Fig. X. a black bristle is represented as intro- 
 duced between the quill and the membrane in contact 
 with it, and a white bristle between the latter and the 
 external vascular membrane. 
 
 D 
 
34 
 
 On Local Action 
 
 It is certain that many parts in the human body 
 occasionally receive an unusually large supply of blood. 
 Mr. Cruickshank mentions, that if the female rabbit, 
 when disposed to admit the male, be killed and ex- 
 amined, the whole uterine system is found black with 
 blood. This phenomenon, and many similar, are in- 
 stances of local action, a term which has indeed often 
 been employed in a wider sense, but which, in the fol- 
 lowing remarks, is restricted to the meaning above 
 illustrated. 
 
 If, in this attempt to elucidate the nature of local 
 action, I should appear to have relied too much upon 
 theoretical reasoning, perhaps I may be permitted to 
 urge, that the case scarcely admits of the evidence of 
 direct observation. 
 
 It will be granted that the cause of local action 
 in any given part is some peculiar condition of the 
 arteries or veins or both in that part, inasmuch as, 
 with the exception of these vessels, the heart is the 
 
 * The substance of these remarks has been introduced 
 in my Anatomical Lectures during the last three years ; 
 and most of the facts in the present number have been 
 mentioned in two courses of lectures. 
 
85 
 
 only organ which influences the flow of blood, and the 
 impulse, which it communicates, is of necessity general. 
 It may likewise be assumed as probable, that the 
 arterial trunks, in a part where local action occurs, 
 if they are involved in it, contribute to its production 
 in a similar manner with their capillary extremities. 
 There can be little doubt that an artery in a living 
 human body is able to contract on a principle not 
 very dissimilar to muscular irritability. One remark- 
 able analogy would indeed suggest a conti’ary opinion. 
 The arteries of a turtle, which are clearly irritable, 
 have a distinct muscular coat, separate from, and in- 
 ternal to a fibrous tunic, which latter resembles con- 
 siderably, and must be compared with, the fibrous coat 
 in human arteries. A muscular coat is found as well 
 in the larger veins of the turtle, which are irritable 
 likewise. But if, where blood-vessels are indisputably 
 irritable, muscular substance enters into their com- 
 position, it is likely that where this texture is wanting, 
 irritability is also wanting *. To this instance, on the 
 other hand, may be opposed still closer analogies 
 drawn from warm-blooded animals. It was remarked 
 
 * It conduces extremely to distinctness in discussions 
 respecting parts, which contract, to limit the terms mus- 
 cular and muscle to express peculiarity of structure. 
 The biceps flexor cubiti is a muscle, the heart is muscular, 
 the detrusor urinae is muscular, the uterus is fibrous, the 
 middle coat of an artery, is fibrous again, but different from 
 either in structure. All these parts, however, are irritable. 
 
 D 2 
 
36 
 
 by Mr. Hunter, that an artery exposed in a living 
 animal gradually contracted. It is well known that if 
 an artery is divided, of a size not to cause syncope, the 
 blood, which at first gushes out in a large stream, 
 after a few pulses is thrown in a stream sensibly 
 narrower, becoming less and less, and finally stopping. 
 This occurrence may be well observed, when artei’ies 
 of the size of a crow-quill are divided in an ass. Again, 
 I have observed that a portion of the carotid artery, 
 upon being removed from a living ass, gradually con- 
 tracts to half its first calibre. 
 
 It would further appear, that the larger arteries may 
 become partially dilated without any apparent injury 
 of their tunics, and, as it would seem, from relaxation 
 only. If the carotid of an ass or large dog be exposed, 
 and rubbed hard, at any point between the finger and 
 thumb, for about half a minute or less, the artery will 
 generally become sensibly dilated at that part. In 
 most instances, in which I have produced this effect, I 
 have subsequently found no lesion whatever in the 
 coats of the vessel ; and I have observed that on cut- 
 ting out a portion of the artery, including the dilated 
 part, the latter contracted gradually and proportion- 
 ately as much as the adjoining tube : in one instance 
 the internal coat was a good deal torn, which led me 
 to vary the experiment. I tied a ligature round the 
 carotid of an ass, so tightly as nearly to cut through 
 both the inner and fibrous coat (as afterwards ascer- 
 tained), and then immediately removed the ligature 
 the blood flowed again through the artery, and, for 
 
37 
 
 the space of ten minutes, during which it was observed, 
 the vessel did not appear in the least dilated at the 
 line, where the ligature had been applied, 
 
 Now the case of local action, which I select as the 
 best illustration of my hypothesis, is the phenomenon 
 of blushing. In this instance, the capillary vessels of 
 a more or less extensive, but partial surface, are found 
 to contain on a sudden more blood than before ; this 
 distention might, it would at first appear, be accounted 
 for equally well on the supposition of the coats of the 
 vessels becoming either relaxed suddenly, or suddenly 
 at some remoter point contracted; but an obstruction 
 to the course of the blood in a lai’ge artery does not 
 produce its enlargement on the side next to the heart, 
 and, therefore, it is probable would not, if occurring 
 in the capillary arteries. Again, blushing is con- 
 trasted with paleness. Of two opposite changes, the 
 causes, it is to be presumed, are opposite; but unques- 
 tionably relaxation of the capillary vessels, or the ab- 
 sence of that usual obstruction, which consists in their 
 narrowness, would not empty their tubes ; and it is 
 surely but consistent with common sense to suppose, 
 that in sudden paleness of the surface, excepting or 
 exceeding what directly results from a feeble action of 
 the heart, the capillaries of the surface are contracted, 
 and that in suffusion of the surface the capillaries are 
 dilated, as the causes of either occurrence. 
 
 But this hypothesis, viz. that relaxation of the coats 
 of arteries is the cause of their containing more blood 
 
38 
 
 at one time than at another, derives its principal sup- 
 port from the facility and completeness, with which it 
 explains all the circumstances characterizing different 
 cases of local action. The vascular tumors, termed 
 aneurysms by anastomosis, seem to form a variety 
 under this head. What is most remarkable respect- 
 ing these tumors is, that when they are cut into, the 
 small vessels in their substance bleed for a longer con- 
 tinuance, and more furiously, than even the small 
 arterial trunks, from which they are derived. Now, it 
 will not be denied, that hemorrhage from small arteries 
 is spontaneously stopped by the contraction of the 
 divided vessels ; but, in the instance before us, the 
 hemorrhage does not cease, or, in other words, the 
 divided vessels do not contract ; and it is then clear, 
 that this occurrence (if the tumor in question form a 
 case of local action) is not inconsistent with the con- 
 jecture, that spontaneous dilatation of arteries is the 
 essence of local action. 
 
 In the enlarging womb, in the mammae, when pre- 
 paring or fitted for their function, in short, in all parts 
 where local action exists or has existed, the arteries are 
 more or less tortuous. It has been supposed by one 
 writer, that the tortuous form of arteries is a provision 
 for an increase of their power, or a means of causing 
 a determination of blood. To me it seems, on the other 
 hand, more likely that this tortuous form is an effect 
 of the change producing local action ; and perhaps the 
 facility, with which the conversion of straight into tor- 
 
39 
 
 tuous arteries may be explained on the assumed hy- 
 pothesis, may be urged as the principal strength of my 
 argument. 
 
 It is obvious that a relaxed vessel, under the or- 
 dinary pressure of the blood, would be affected in the 
 same way with a vessel not relaxed, under extra- 
 ordinary pressure. Now, the latter case may be easily 
 examined : when the carotid of an ass is exposed, and 
 the animal put to no farther suffering, in a short time 
 the artery is nearly at complete rest; there is little 
 sensible alteration in its form or place, at each pul- 
 sation of the heart : if at this period the animal be put 
 in pain, it struggles, the heart beats more vigorously, 
 and immediately the carotid artery is thrown into a 
 waving line, or becomes elongated and tortuous at 
 each contraction of the ventricle ; and thus, it may be 
 presumed, would an artery, the fibrous coat of which 
 should be relaxed, during the ordinary action of the 
 heart, become elongated and tortuous likewise; and, 
 consistently with the accommodating and modelling 
 power of the body, in time permanently assume the 
 form, to which it had at first been violently extended. 
 In explaining on this principle the gradual increase of 
 tortuousness in the temporal arteries, I have not to 
 advert to any supposed difficulty in the ascent of the 
 blood along these vessels (it being clear that gravity 
 favours the entire course of the blood in those parts the 
 veins of which descend), but simply to notice the fre- 
 quency of local action in the head, as proved by the 
 distinctness, with which the temporal arteries throb 
 
4.0 
 
 on any casual excitement of the mind. The per- 
 manent and original curves of the internal carotid 
 and vertebral arteries, secui’ed by the forms of their 
 channels in bone, are obviously contrivances of a very 
 different nature. There can be no doubt, looking to 
 the thin coats of the vessels of the brain, and to the 
 analogy of the rete mirabile, that the double curve of 
 each of these arteries, in human beings, is intended 
 for the mechanical diminution of the force of the 
 blood circulating in the brain. 
 
 One other case remains to be considered, in con- 
 nexion with the subject of local action. In the aneu- 
 rysmal varix the artery is found to be larger than 
 before, and is said to be somewhat tortuous. I must, 
 in this case, refer to the beneficent provisions of na- 
 ture, many of which, even after the impairment of 
 the human frame, directly tend to its renovation or 
 support ; and I would assume, that the artery is, in 
 this case, specially relaxed through such an influence 
 as regulates the action of the heart, in order that a 
 competent supply of blood be conveyed to the limb, 
 over and above that necessary to fill the vein, with 
 which the artery communicates; an assumption at 
 least consistent with the facts of the case. 
 
 With regard to the enlargement and tortuousness 
 of the veins, in cases of local action, it is clear that 
 there is nothing in these circumstances, which militates 
 against my hypothesis. The effect of pressure upon 
 veins is known to render them large and tortuous ; as 
 when a ligature is habitually tightened round a limb : 
 
41 
 
 but it stands to reason, that, if the capillaries in a 
 part are enlarged, the blood passing through them 
 with less resistance than before, must exert more 
 pressure upon the veins of that part. 
 
 In the preceding remarks, I have confined myself, 
 as I proposed, to cases, in which the blood flows with 
 more than usual freedom to a given part; a state 
 which may or may not be conjoined with inflam- 
 mation, with abundant, defective, or vitiated secretion ; 
 but which is obviously something quite distinct from 
 each of these occurrences. 
 
42 
 
 Remarks in Defence of the Hunterian Theory of 
 Absorption. 
 
 The principal argument adduced in favour of the 
 theory that absorption is performed by the lymphatic 
 and lacteal vessels alone, is the following; that, as 
 the lymphatics and lacteals are of similar structure, 
 and pass alike through similar gland-like bodies, unite 
 finally, and open by the same channel into the veins, 
 it is analogically probable that their uses are alike : 
 but the lacteals are known to be absorbent vessels, 
 inasmuch as the chyle, which is formed in the small 
 intestine, may be detected both in their minute orifices 
 and in their trunks ; and the lacteals, again, are likely 
 to be the only absorbent vessels, as the chyle is not 
 found in the mesenteric blood-vessels : the lymphatics, 
 it is then analogically inferred, are absorbents like- 
 wise, and probably, with the lacteals, constitute ex- 
 clusively the absorbent system of the body. 
 
 In further confirmation of this opinion, Mr. Hunter’s 
 experiments'*^ went to prove, that milk, or a solution 
 of starch and indigo, introduced into the intestine of 
 a living animal, is found subsequently in the lacteals. 
 
 * Medical Commentaries, by Dr. William Hunter. 
 
43 
 
 but not in the veins of the mesentery. M. Majendie 
 found, that these experiments did not succeed on 
 repetition. I have recently repeated them, and re- 
 marked an incident, which perhaps may have deceived 
 Mr. Hunter in one case. When the mesentery is 
 drawn out from the abdomen of a living animal, the 
 lacteals generally contain more or less chyle : after a 
 short exposure of the part, the colour of the lacteals 
 changes fi'om white to a clear blue. The first time 
 that I observed this occurrence, it was subsequent to 
 my having introduced a solution of starch and indigo 
 into the adjoining intestine ; and I concluded that an 
 absorption of that substance had taken place ; but, on 
 scrutinizing the appearance narrowly, I found that 
 the blue vessels contained no fluid, but were, in fact, 
 empty ; and I have since ascertained that the lacteals 
 in adult asses, dogs, and rabbits, uniformly appear 
 blue when empty, unless a light-coloured surface is 
 placed beyond them. In the case in which Mr. 
 Hunter observed the absorption of a white fluid, I am 
 inclined to suppose, that the intestine contained, pre- 
 viously to the operation, more or less chyle, which, 
 being afterwards absorbed, was supposed to be nfllk : 
 at any rate, on throwing milk, diluted with a little 
 hot water, into a carefully-washed portion of the small 
 intestine of a young ass, which was then retained in 
 the abdomen half an hour, I observed, no absorption 
 of a white fluid to ensue. 
 
 !N1. Majendie, in continuing this inquiry, made 
 some interesting experiments, which are well known. 
 
44 
 
 to prove that veins absorb. It was found that odorous 
 substances, and poisonous solutions, found their way 
 into the blood, when introduced into a portion of in- 
 testine, the communication of which with the system, 
 except through a vein and artery, was entirely in- 
 terrupted : whence M. Majendie inferred that the 
 veins absorb ; and in truth, without M. Majendie’s 
 own assistance, it would have been difficult to have 
 escaped from this conclusion ; for physiologists had as- 
 sumed that transudation cannot take place in a living 
 body ; and though it is now clear, on a moment’s re- 
 flection, that this assumption is untenable, and that 
 the onus of proof lies with those who would assert it, 
 not with those who disclaim it, it was left for M. 
 Majendie and his immediate school to execute several 
 very curious experiments, which lead to the opposite 
 opinion, that transudation really occurs in living tex- 
 tures*. 
 
 But this principle once admitted, there is an end 
 to the conclusiveness of M. Majendie’s experiments, 
 as decisive of venous absorption ; and the broad ana- 
 logical argument advanced by the Hunters to esta- 
 blish the position, that the lymphatics and lacteals 
 form exclusively the absorbent system, remains un- 
 shaken. It must not be lost sight of, that the en- 
 trance of any substance, raw and unassimilated, into 
 the veins and arteries, is a very different occurrence 
 
 Journal de Physiologie experimentale. 
 
45 
 
 from the conversion of the elements of the human 
 body into lymph, and their subsequent readmixture 
 with the blood ; and, again, that the refusal of the 
 lacteals to take up milk or starch, does not disprove 
 that these vessels habitually absorb unchanged, and, 
 in addition to the chyle, such simple fluids, as may be 
 carried without detriment into the circulation. 
 
I 
 
 46 
 
 Examination of a Body soon after Parturition. 
 
 The following account was drawn up, at my re- 
 quest, by my friend and pupil Mr. Taylor, who dis- 
 sected the body, in which the appearances described 
 below occurred. 
 
 In October last the body of a female, apparently 
 about the age of thirty, was brought into Mr. Mayo’s 
 dissecting room ; it was fat and muscular, not in any 
 ways mishapen, and somewhat above the middle 
 height of women. This pei’son appeared to have died 
 of uterine hemorrhage, a short time after delivery at 
 the full period, for the uterus was very capacious, its 
 substance 6-lOths of an inch in thickness, its orifice 
 open, and, when disposed in a circular form, about 
 two inches in diameter. Both the uterus and vagina 
 contained a quantity of clotted blood. The inner sur- 
 face of the uterus was thinly covered with shaggy 
 processes of flocculent membrane, and appeared 
 abi’aded here and there, and when the part was in- 
 jected with size and vermilion, the injection escaped 
 into the cavity of the womb, through many small 
 orifices on its inner surface. 
 
 The muscles of the abdomen were fouad to have 
 their usual appearance, except that the recti were be- 
 tween four and five inches asunder. 
 
47 
 
 It was ascertained that the upper part of the vagina, 
 where it joins the uterus, could be readily exposed 
 without injury to the peritoneum, after an oblique 
 incision through the fore part of the abdominal 
 parietes. 
 
 The pelvis was well formed, and of the usual dimen- 
 sions ; but it was found that the sacro-iliac joint on 
 either side was loose, so that the ileum and sacrum 
 could be separated on each side to the extent of a third 
 of an inch on the fore part of the joints The liga- 
 mentous fibres, which run across from the ileum to 
 the sacrum, were entire; but the usual connecting 
 medium within, between the bony surfaces, was dis- 
 solved. 
 
 The symphysis of the pubes had been cut through 
 before the condition of the sacro-iliac joint had been 
 noticed. The sacro-sciatic ligaments were very lax» 
 
48 
 
 Inquiries respecting the Structure of the Human 
 Brain, by Professor Beil. Archiven fur die Phy- 
 siologic. Neunter-band, p. 136 — 208. 
 
 VIII. 
 
 I BELIEVE that I have successfully ascertained the 
 structure of the greater part of the brain, namely, of 
 the nucleus and convolutions of either hemisphere. I 
 shall describe the former in the present treatise, and, 
 subsequently, the remaining smaller parts, the an- 
 terior commissure, the fornix, the optic thalami, and 
 the tubercula quadfigemina. I am sensible that my 
 researches are in several points incomplete. The 
 connexion between the nucleus of the brain and its 
 convolutions, between that of the cerebellum and its 
 laminated surface, has escaped me. I had nearly de- 
 spaired of making any thing of the chain of ganglia, 
 which occur in the brain; but latterly I have found out 
 methods of examining those parts, which promise more 
 success. I leave, for my last object, the final distribu- 
 tion of the vessels in the brain ; an inquiry, which ap- 
 pears to me one of the greatest moment, and calculated 
 to throw light on any remaining obscurities. 
 
 I am particular in describing the various methods, 
 which I have adopted in preparing and dissecting 
 brains, in order that every one may have it in his 
 
49 
 
 power to verify with facility my remarks. At first 
 I tore the brain in various ways, trusting to chance 
 for a fortunate rent ; but the appearances thus pro- 
 duced differed in each prepai’atioii, and I could not 
 obtain a second result similar to the first. I now am 
 able to point out definite methods, by which the 
 organization both of the brain and cerebellum can be 
 distinctly and readily shown at pleasure. The method 
 adopted by Gall is insufficient. The brain without 
 some preparation is not firm enough to allow of the 
 separation of its parts, and contains, unquestionably, 
 like the chrystalline, many layers, the distinction be- 
 tween which is not evident till the part has been 
 coagulated. Very likely thei'e exist still better me- 
 thods of preparing the brain than those, which I have 
 employed. Macei-ation in alkohol reduces the organ 
 to S-d-ths of its oi’iginal volume, and this circumstance 
 may interfere with the ready separation of its parts. 
 Maceration in an alkaline solution diminishes indeed, 
 but does not obviate entirely the contraction produced 
 by alkohol when employed alone. Maceration in acid 
 solutions, which are of so much use in unfolding the 
 composition of nerves, is inapplicable to the brain. 
 Both sulphuric and muriatic acid in water render the 
 brain too brittle for tracing the course of its fibres, 
 and can only be employed, with any advantage, on 
 small portions of the brain, or on those parts which 
 are composed of parallel fibres. 
 
 Of the methods which I have employed in preparing 
 brains, those contained in the following directions 
 
 E 
 
50 
 
 answered best: 1. Let the brain be hardened in al- 
 kohol, and then placed in a solution either of car- 
 bonated or pure alkali, in the latter two days, in the 
 former for a longer period, and then again hardened 
 in alkohol, if thus rendered too soft. The advantage 
 of this method is, that the fasciculi of nervous matter 
 are more readily separable, and the brown matter 
 more distinguishable from the white, than after simple 
 maceration in alkohol : the gray matter is rendered 
 by the alkali of a blacker gray, and assumes the con- 
 sistence of jelly. 2. Let the brain be macerated in 
 alkohol, in which pure or carbonated potass or am- 
 monia has been previously dissolved : the contraction 
 of the brain is lessened by this process. 3. Let the 
 brain be macerated in alkohol from six to eight days, 
 and then its superficial dissection commenced, and 
 the separation of the deeper parts continued, as the 
 fluid, in which the brain is kept immersed, penetrates 
 its substance. This method appears to me better 
 than the preceding, and would very likely be im- 
 proved, if the alkohol were rendered alkaline. The 
 fibres in a brain, thus prepared, are more tenacious 
 than otherwise, and the deeper parts are sooner ex- 
 posed to the influence of the alkohol. The epi- 
 thelium tends especially to prevent the penetration of 
 the alkohol ; it would be well always to remove it en- 
 tirely or in part from the surfaces of the brain, which 
 it covers. Specimens of the cerebellum, which have 
 remained several years in alkohol, sometimes exhibit 
 with unusual distinctness the fasciculated structure. 
 
51 
 
 I have not yet tried other methods, such as macera- 
 tion in solutions of corrosive sublimate, and of liver 
 of antimony, the application of heat, dissection under 
 water, and the like, which may perhaps exceed those, 
 which I have adopted. 
 
 I have used, as instruments in dissection, my fingers 
 alone, the handle of a scalpel, a pointed instrument, 
 an ivory knife, rounded at the extremity, and another 
 with a straight edge, and a curved and half-sharpened 
 back : these instruments are to be employed upon the 
 layers that cover the surface, which it is desired to 
 expose, and the parts are to be so bent as to throw 
 forward the surface, of which the dissection is to be 
 made. 
 
 It has struck me that preparations in wax might 
 be of service in representing the various appearances, 
 which are made out by dissection of the hardened 
 brain. 
 
 Let me now explain various terms, which I have 
 found it convenient to employ in the description of 
 the brain. 
 
 The epithelium is a leathery substance, partly 
 membranous, partly consisting of nervous matter, 
 which invests such medullary surfaces of the brain, as 
 want other coverings. 
 
 The medulla incognita [ungenannte marksubstanz] 
 is placed near to, and somewhat parallel with, the 
 optic nerves. 
 
 The hamular fasciculi [haakenfbrmige markbundel] 
 
 E 2 
 
52 
 
 connect the anterior and middle lobes of either hemi- 
 sphere at the entrance of the fissura Sylvii. 
 
 The covered bands [bedeckten bander] are situated 
 on either side of the raphe, within the two convolutions, 
 which are in immediate contact with the corpus cal- 
 losum. 
 
 As belonging to the fornix [zwillingsbinde des 
 balkens] may be noticed, its root in either thalamus, 
 its nodules the corpora albicantia, its anterior crura, 
 its body, or that part where the lateral portions cohere 
 together, the part termed the lyra, and the posterior 
 crura, terminating in the hippocampi. 
 
 The island [insel] is the oval floor of the fissura 
 Sylvii, on which are placed small and low convolu- 
 tions, surrounded by a furrow : the entrance of the 
 fissura Sylvii is its lower and anterior extremity. 
 
 The corpus striatum [gestreifte vbrdere, grosse hirn- 
 ganglium] consists of two parts, one external, the 
 other internal to the substance derived from the crus 
 cerebri. 
 
 The medullary capsule [kapsel] is the substance 
 immediately enclosing the outer portion of the corpus 
 striatum : the external part of the medullary capsule 
 is that surface, which supports the convolutions of the 
 island. 
 
 The corpus callosum is terminated by an anterior 
 fold [das knie des balkens], the extremity of which is 
 narrowed [das schnabel], and again by a posterior 
 fold [die aufgesetzte wulst]. 
 

 I 
 
 The tapetum [tai^ete] of the corpus callosum is a 
 layer derived from/ it to line the roof of the posterior 
 horn of the laterall ventricle. 
 
 The fibres dcjiaved from the crus cerebri, which 
 diverge at the upper margin of the thalamus towards 
 the circumference of either hemisphere, form the 
 fibrous cone [stabkranz]. 
 
 The disposition of the fibres in the brain is various ; 
 those in the convolutions are disposed in medullary 
 plates, which are arranged on the same principle with 
 the plates in the laminae of the cerebellum ; but there 
 is some difference and more intricacy in the structure 
 of the convolutions, from the circumstance that the 
 latter are not parallel with each other, but unite at 
 various angles. In the anterior commissure, and in 
 the fornix, the fibres are flax-like and reticular, in the 
 crus cerebri and corpus callosum they are disposed in 
 parallel flattened fasciculi; in the outer wall of the 
 medullary capsule, the fibrous cone, and the tapetum, 
 their disposition is radiated. 
 
 The cerebrum is placed upon the crura cerebri like 
 the top of a mushroom upon its stalk. Like the cere- 
 bellum, the cerebrum consists of a nucleus, in which 
 the ventricles are contained, of parts, in this case called 
 convolutions, which are external to the nucleus, and 
 of gray substance, which lies partly within, partly on 
 the surface. 
 
 The nucleus is composed again of the parts con- 
 tinuous with the crura cerebri, or vertical portion, 
 and of the corpus callosum, and fornix, or horizontal 
 
64 
 
 portion. These, with the convolutions, and their gray 
 matter, appear to constitute the e^ssential elements of 
 the brain ; the rest to be only for tlfie purpose of esta- 
 blishing communication between re^note parts. Thus, 
 between the nucleus and the convolu(tions, a medullary 
 layer exists, specially observable nearlthe fissura Sylvii, 
 which consists of distinct fasciculi extending between 
 distant convolutions. 
 
 IX. 
 
 Of the vertical Portion of the Nucleus. 
 
 The whole extent of the vertical part of the nucleus 
 on either side of the brain, from the beginning of the 
 pyramid to the bases of the convolutions, forms a single 
 organ ; in the same way the horizontal part of the 
 nucleus forms another complete organ. 
 
 The pyramids are parts of the medulla oblongata ; 
 at the fore part of which, about ten or fifteen lines 
 below the annular protuberance, several medullaiy 
 fasciculi cross obliquely over from one side to the 
 other. This decussation is best exposed by partially 
 separating the lateral portions of the medulla ob- 
 longata from behind at the calamus scriptorius, when 
 the white fibres alluded to are seen to join the nucleus 
 of the spinal marrow a few lines below their crossing, 
 and above it to form the pyramids. Like the crura 
 cerebri, and the corpus callosum, the pyramids appear 
 to consist of parallel medullary fasciculi, which, in the 
 
55 
 
 latter case, form two fibrous cylinders ; these are con- 
 tracted just before they enter the annular protuberance, 
 
 , in which their fibres are again spread out, and form 
 several layers interwoven, at right angles, with the 
 transverse fibres derived from the cerebellum. 
 
 Beyond the annular protuberance, the white fasciculi 
 derived from the pyramids continue to ascend, forming 
 the anterior and inferior surface of the crus cerebri, 
 external to which are seen the fillet and the corpora 
 geniculata on either side. Upon detaching and 
 turning aside the tractus opticus, the superficial fibres 
 of the crus cerebri are found extending towards the 
 posterior and inferior horns of the lateral ventricle. 
 Behind the transverse fibres of the annular protuber- 
 ance, and between the middle peduncles of the cere- 
 bellum, or at the floor of the fourth ventricle, covered 
 only by gray matter, is found a’ thick and broad 
 stratum of longitudinal fibres, which, in its ascent from 
 the medulla oblongata, is joined on either side by the 
 fillet. These two substances are as yet unconnected 
 with the pyramids, but, subsequently, contribute to 
 the radiation of the vertical part of the nucleus. At 
 the angular hollow, from whence the third pair of 
 nerves emerges, a medullary fasciculus often separates 
 itself from the ascending fibres, and passes round the 
 crus cerebri in a direction from within outwards. 
 
 The fasciculi of the vertical portion, from their 
 entrance into the annular protuberance upwards, are 
 continually enlarging and diverging, but to a more 
 remarkable degree after they emerge from that body. 
 
 
56 
 
 If a transverse section be made of the crus cerebri, 
 it appears that the nervous fibres derived from the 
 pyramid form a thick inferior crust, disposed in 
 flattened longitudinal fasciculi, the edges turned in- 
 wards and outwards; above which, and inclosed by 
 it, a distinct and more or less cylindrical mass [der 
 baube, it may be called the cylinder of the crus 
 cerebri,] occurs, which comprises all the parts situated 
 at the floor of the fourth ventricle between the lateral 
 peduncles of the cerebellum, the black substance, the 
 tubercula quadrigemina, the thalamus, and, lastly, the 
 inner portion of the corpus striatum. If a section of 
 the crus cerebri be alternately dried and reimmersed 
 in alkohol, the layers of the crust may readily be 
 peeled off from the remaining part, and are found to 
 extend to the depth of two lines. 
 
 The vertical portion of the nucleus is throughout 
 connected with gray matter, which in part covers it, 
 and in part is interwoven with its medullary sub- 
 stance ; thus, above the pyramids, is placed the gray 
 substance of the medulla oblongata ; and in the an- 
 nular protuberance gray matter intervenes between 
 the separated fibres. Above the annular protuberance, 
 the ascending fasciculi are clothed internally with 
 the gray matter, which extends backward from the 
 corpus striatum, along the third ventricle, to the 
 margin of the annular protuberance. On the outside 
 of the ascending fibres, gray matter, from the tubercula 
 quadrigemina, extends downwards and backwards 
 with the fillet ; and between the anterior and lateral 
 
57 
 
 peduncles of the cerebellum, reaches the annular pro- 
 tuberance, with the gray matter of which it is con- 
 tinuous. The black matter again is interposed between 
 the crust and cylinder of the crus cerebri, and seems 
 to give origin to the third pair of nerves. Further 
 forward, the fasciculi of the vertical portion of the 
 nucleus are covei’ed by the tubercula quadrigemina, 
 and by the thalami, and are finally, in great part, 
 lodged between the two portions of the corpus stri- 
 atum ; from either of which cross processes of gray 
 matter pass through the ascending medulla. 
 
 The fillet of either side, traced from the annular 
 protuberance upwards, divides into two portions, one 
 of which passes inwards, to join its fellow of the op- 
 posite side, so as to form a curvilinear stratum of 
 fibres immediately below the tubercula quadrigemina : 
 the other plunges below the corpus geniculatura in- 
 ternum, into the thalamus of the same side, and extends 
 apparently to join the fibrous cone. Below the fillet, 
 again, the anterior peduncle of the cerebellum extends 
 in a direction inwards and downwards towards the 
 black matter, to contribute, probably, to the radiation 
 of the vertical portion. Either thalamus consists of 
 several layers, each layer of gray and white matter, 
 the former internal. The superficial layer has a fibrous 
 structure, and peels off readily in the direction from 
 before backwards. Between this and the next the 
 root of the fornix lies ; so that by tracing the latter 
 from the corpus albicans the interval between the two 
 inner layers is at once found. The superficial layer 
 
58 
 
 is continuous behind with the tractus opticus, with the 
 fibres, which, clothed with the tapetum, form the 
 roof of the inferior horn, and above with the tasnia 
 semicircularis geminum : the latter substance is a cord 
 of flax-like fibrils, which extends forwards to where 
 the crus of the fornix meets the septum lucidum, be- 
 hind the anterior commissure; it is in contact with 
 the fibi’ous cone ; it assists in forming the tapetum of 
 the inferior horn of the lateral ventricle, and it gives 
 fibrils to the tractus opticus. The second layer is a 
 production of the corpus geniculatum internum, which 
 expands either way, so as to inclose the posterior margin 
 of the crus cerebri ; its outer fibres, passing towards the 
 outer portion of the corpus striatum, join the fibrous 
 cone. The third layer is that derived from the fillet, 
 which has been already spoken of. The substance of 
 the thalamus is thickest below ; the white fibres, which 
 proceed from its internal substance, ascend obliquely 
 outwards, and at the upper and outer margin of the 
 thalamus unite with the fibrous cone, partly interlacing 
 with, and decussating that substance, as may be seen 
 on x'aising in succession, after dividing the crus cerebri, 
 in a separated hemisphere, the first, second, and third 
 layers of the thalamus, and carrying the rent forward : 
 then, too, is seen the regular disposition in parallel 
 fasciculi, which the crust of the crus cerebri maintains, 
 till, blending with the fibres last described, it with 
 these forms the fibrous cone, whence are derived 
 fasciculi towards the circumference of the hemisphere, 
 the longest to the posterior, and the next in length to 
 
59 
 
 the anterior lobe. At the entrance of the fissura 
 Sylvii, this arrangement, otherwise uniform, is in- 
 terfered with ; an obscurely organized substance, the 
 medulla incognita, [ungenannte Marksubstanz,] oc- 
 cupies this surface in the base of the brain; it con- 
 tains part of the anterior commissure, is continuous 
 before with the thalami, laterally with the pes and 
 taenia hippocampi, and thus encircles the outer margin 
 of the crus cerebri, being exposed on the removal of 
 the tractus opticus. 
 
 The anterior and middle parts alone of the fibrous 
 cone are enclosed between the two portions of the 
 corpus striatum ; for this extent its outer fibres form 
 the inner surface of the medullary capsule. In the 
 entire vertical process, the coarser fasciculi, which are 
 formed by the union of many delicate fibrils, resemble 
 more or less, but most in the crus cerebri, the sticks 
 of a fan ; these flattened fasciculi, from the annular 
 protuberance to the fibrous cone, are disposed some- 
 what circularly, their edges looking inwards and out- 
 wards ; but in the fibrous cone their disposition more 
 resembles that of the sticks in a closed fan ; they at 
 first, at least, lie nearly in one vertical plane ; each 
 fasciculus has a distinct but delicate sheath of cellular 
 membrane *. The fasciculi of the fibrous cone con- 
 
 * The epithelium consists of a fine transparent pro- 
 duction of the pia mater, and a layer of nervous matter 
 within this, either white or gray ; it admits of very distinct 
 
60 
 
 tinually diverge in their course towards the circum- 
 ference of the brain. The foremost fasciculus attaches 
 itself to the curved central part of the anterior com- 
 missure ; or the anterior commissure passes between 
 the first fasciculi of the fibrous cone, and then spreads 
 itself out in the under surface of the middle lobe. 
 The anterior fasciculi are long and delicate; the 
 middle fasciculi the shortest and the thickest, being 
 moi'e cylindrical, and principally employed in the 
 formation of the pecten; the posterior fasciculi are 
 the longest ; those which pass to the neighbourhood 
 of the infei’ior horn are somewhat shorter; the two 
 latter sets are not interwoven with gray matter; the 
 two former alone are interposed between the outer 
 and inner portions of the corpus striatum, cross 
 processes from which interlace with the medullary 
 fasciculi for this extent: the largest of these cross 
 processes is the foremost among them ; this series of 
 
 demonstration on the septum lucidum. Where the corpus 
 callosum joins the outer margin of the corpus striatum, 
 the epithelium appears to split into two layers ; one of 
 which invests the inner surface of the corpus striatum, 
 the other passes between its gray matter and the fibrous 
 cone, each fasciculus of which it seems to clothe down 
 to the margin of the optic thalamus. It is probable, so 
 general is the obvious distribution of the membrane, that 
 each plate, even in the convolution^, has a tunic derived 
 from it. 
 
61 
 
 intersections forms the pecten ; it sometimes reaches as 
 far back as the posterior margin of the optic thalamus ; 
 fine medullary processes, derived from the tenia, pass 
 outwards into the pectea, in a similar direction with 
 the gray processes. Upon the outer margin, likewise, 
 of the corpus striatum a substance is found, which 
 fills the interval at the meeting of the vertical and 
 horizontal portions of the nucleus, where the middle 
 fasciculi of the fibrous cone are bending forwards : it 
 eventually joins the tenia semicircularis ; after which, 
 with the tenia, it passes around the outer margin of 
 the thalamus along the inferior horn of the lateral 
 ventricle, uniting finally with the medulla incognita. 
 From this last described substance, again, medullary 
 fibrils, every where mixed with gray matter, are given 
 off, which pass, like teeth, into the pecten. 
 
 The foremost fasciculi of the fibrous cone pass 
 straight towards the corpus callosum ; those which are 
 next in order, on its internal surface, have an in- 
 clination forward, which takes place in the structureless 
 layer just mentioned as lying at the exterior margin 
 of the corpus striatum; these internal fasciculi ap- 
 parently proceed from the thalamus; the external 
 fasciculi, which are derived from the crus cerebri, 
 pass in a straight direction. The posterior fasciculi 
 of the fibrous cone, which are immediately clothed by 
 the tapetum, pass horizontally from the posterior 
 margin of the thalamus towards the point of the 
 posterior lobe, are from two to three lines in thick- 
 ness, and several inches in length. The fasciculi 
 
62 
 
 which extend to the middle lobe are inclined down- 
 ward, and those which belong to its anterior ex- 
 tremity are again somewhat inclined forward. The 
 fasciculi of the fibrous cone radiate from the thalamus 
 as from a centre, and their direction varies with the 
 inclination of its mai’gin. The posterior extremity of 
 the thalamus divides into two parts, one of which, that 
 namely continuous with the tractus opticus, covers 
 the other, which is obtuse, and contributes to form 
 the roof of the inferior horn. The radiated ex- 
 pansion of the anterior commissure blends with the 
 fasciculi of the fibrous cone. In order to show this 
 circumstance, the anterior commissure must be ex- 
 posed, the tractus opticus turned back, and the fas- 
 ciculi of the crura cerebri, which it covered, followed 
 in their upward and outward course. At the roof of 
 the inferior horn there are found, besides the epi- 
 thelium, the tapetum formed from the corpus cal- 
 losum and tasnia semicircularis geminum ; then a layer 
 derived from the obtuse end of the thalamus; and 
 finally the layer derived from the crus cerebri and the 
 anterior commissure. Externally to all these a layer 
 of long fibres is found to extend from the fore part of 
 the middle lobe to the extremity of the posterior lobe, 
 where it blends with those of the fibrous cone. The 
 portions of the latter belonging to the inferior and 
 posterior horns lie quite behind the outer portion of 
 the corpus striatum, but are covered for a short extent 
 by the tail-like prolongation of the inner portion. 
 Hence they are not traversed by transverse processes 
 
63 
 
 of gray matter, but the fasciculi are uniformly in close 
 apposition. From the portion included between the 
 two parts of the corpus striatum, very fine filaments 
 are derived, which penetrate the substance of the 
 latter. 
 
 The posterior fasciculi of the fibrous cone, extend- 
 ing along the outside of the posterior horn, finally lose 
 themselves in the neighbouring convolutions. Its 
 anterior fasciculi are joine’d from without by the fibres 
 radiating from the outer wall of the capsule ; both to- 
 gether, intermingled and interwoven, extend to the 
 corpus callosum. Where the two systems join, a 
 ridge is left on breaking away the investing substance, 
 as when the hemispheres are rent away from the upper 
 surface of the corpus callosum. Behind, the radiation 
 of the outer wall of the capsule blends with that of the 
 fibrous cone, and near the inferior horn to both are 
 joined the radiation of the anterior commissure. 
 
 To prepare for this demonstration, a brain separated 
 from the cerebellum by a section of its crura, and de- 
 prived of its upper part, by an horizontal section above 
 the corpus callosum, stripped of its membranes, and ver- 
 tically opened from its base by a section in the median 
 plane, extending to the fornix, or even so divided, and 
 either posterior horn longitudinally cut into, is to be 
 hardened in alkohol, then softened as above described, 
 and rehardened. A person accustomed to this dis- 
 section may begin it with advantage on a brain only 
 eight days hardened in alkohol, taking care to stop 
 
G4 
 
 where the alkohol has not yet coagulated the medullary 
 substance. 
 
 The first step in the dissection is to expose the 
 outer wall of the medullary capsule, in the manner 
 presently described, with the course of the anterior 
 commissure to the middle lobe. The brain may then 
 be readily spread open from below. The epithelium 
 is afterwards to be removed from the under surface of 
 the corpus callosum : that covering the corpus striatum 
 in the lateral ventricle to be cut through longitudinally, 
 and one half drawn off towards its upper margin, the 
 other tov/ards the thalamus. The taenia semicircularis 
 geminum is then to be raised in the direction from 
 behind forwards, by which means the pecten is ex- 
 posed. In a similar manner the inner portion of the 
 corpus striatum is to be raised, into which delicate 
 fibrils may then be seen to enter from the fibrous 
 cone, which is denuded by its removal ; and next, the 
 structureless medullary substance, in which part of 
 the ascending fasciculi are incurvated forward, and 
 which lies along the upper margin of the inner portion 
 of the striated body. The separation being now 
 carried down to the fore-part of the anterior com- 
 missure, exposes the foremost fasciculi of the fibrous 
 cone, before which the two portions of the corpus 
 striatum arc seen to unite by means of a broad process. 
 Then, in the opposite hemisphere, the taenia semi- 
 circularis geminum may be raised so as to show the 
 toothlike processes derived from it, and entering the 
 
65 
 
 pecten. The cauda of the inner portion of the corpus 
 striatum may be next removed, the thus exposed edge 
 of the tapetum divided, a section of the tapetum carried 
 to the point of the posterior horn, and either portion 
 of it turned aside. To show the organization in the 
 inferior horn, the tractus opticus is to be turned back 
 to its corpus geniculatum, and the obtuse extremity of 
 the thalamus thus exposed, which radiates above the 
 tapetum into the inferior horn. Through these means 
 are brought into view the outer and upper packets of 
 the crura cerebri, which bend backwards abruptly, and 
 expand themselves above the last described stratum, 
 with which they blend. The outer surface of the 
 vertical portion of the nucleus yet remains to be 
 shown. The medullary capsule is already exposed : 
 the medulla incognita is now to be pressed away from 
 the crus cerebri from behind forward, the anterior 
 commissure to be cut through, the anterior crus of 
 the fornix laid bare to the corpus albicans, the outer 
 wall of the capsule to be removed, and the gray matter 
 within it extruded. It remains to raise the tubercula 
 quadrigemina in the course of the anterior peduncles 
 of the cerebellum, to separate, from within, layer after 
 layer of the thalamus, till the black substance is ex- 
 posed, which lines the fibres derived from the pyramids, 
 in order that the union of the thalamus with the crus 
 cerebri may be fully elucidated. 
 
 F 
 
GG 
 
 X. 
 
 Of the liGh'izontal Portion of the Cerebral Nucleus. 
 
 To either surface of the corpus callosum three 
 longitudinal bands adhere. Above, and in the median 
 plane of the body, the superior raphe extends from 
 the anterior to the posterior fold of the corpus cal- 
 losum ; below, and opposite to this, a similar band is 
 found, like the former, furrowed centrally; to the 
 edges of its furrow the two layers of the septum 
 lucidum are attached; behind, the inferior raphe con- 
 tinues in a straight direction to the posterior fold of 
 the corpus callosum, blending with which and with 
 the fornix it terminates. In its course it appears to 
 give and receive fibrils from the corpus callosum. 
 Between the superior and inferior raphe, or in the 
 median plane, the corpus callosum is rather con- 
 tracted, and its fasciculi are more closely woven. 
 
 Parallel with, and on either side of the superior 
 raphe, may be found a flattened medullary fasciculus, 
 which, lying concealed by the convolution in contact 
 with the upper surface of the corpus callosum, is 
 termed the covered band. The convolution alluded 
 to may be traced from the fore and lower part of the 
 anterior lobe, where it is reflected forward from the 
 convolution touching the root of the olfactory nerve ; 
 thence advancing forward and overlapping the an- 
 
67 
 
 terioi’ fold of the corpus callosum, then continuing 
 along its upper surface in a line unbroken, except to- 
 wards the posterior fold by some vertical indentings, 
 and finally sweeping downward and forward again, 
 and skirling the aperture of the inferior horn. Either 
 posterior crus of the fornix, which is at first com- 
 posed of medullary substance alone, derives from this 
 extended convolution a supply of gray matter, which 
 is contained in its navicular cavity, and thus the 
 hippocampus major is formed. When this convolu- 
 tion is turned aside, the covered band is seen, which 
 may easily be raised from its adhesion to the corpus 
 callosum : externally to it the fibres of the latter lose 
 their former fasciculation, and are arranged in delicate 
 plates, more closely attached to each other. The 
 covered band of either side turns round the anterior 
 fold of the corpus callosum, extends to the anterior 
 commissure, and brings away with it, when raised, all 
 the convolutions which belong to the inner and central 
 part of the anterior lobe: in like manner it turns 
 round the posterior fold, becomes continuous with 
 the posterior crus of the fornix and the long convo- 
 lution above described. Thus on either side the 
 covered band forms a circle round the root of the 
 hemisphere, unbroken except at the entrance of the 
 fissura Sylvii. To show the covered bands, it is con- 
 venient to make an horizontal section of a prepared 
 hemisphere, as for the exposure of the centrum ovale 
 minus ; then vertically to divide the long convolution 
 
 F 2 
 
G8 
 
 and the covered band itself : the latter may be raised 
 from this point in either direction. 
 
 The fornix on the under surface of the corpus cal- 
 losum is to be compared with the covered bands of 
 the upper. The use of these parts is apparently that 
 of longitudinal commissures. 
 
 The corpus callosum has a similar structure with the 
 crust of the crura ; it consists of flattened fasciculi, which 
 are disposed transversely with their edges turned 
 upward and downward : hence the appearance of 
 transverse grooves on the surface, the readiness of 
 tearing this substance across, and the impossibility of 
 accomplishing this evenly in any other direction. 
 Each flat fasciculus consists of many delicate plates. 
 The closer grain of this substance in the median plane 
 is particularly well seen at the concave surface of the 
 anterior fold, from which, as from a centre, the fas- 
 ciculi seem to radiate in all directions. The texture 
 of the corpus callosum is coarse within, and fine 
 without the covered bands. No one fasciculus is 
 entire and disconnected, but gives to and receives 
 fibrils from those adjoining, aS may be seen on drawing 
 asunder the extremities of the corpus callosum. There 
 exist likewise in its substance fasciculi much finer 
 than the general run of the coarser fasciculi, which 
 yet are as separable and distinct as the latter. 
 
 The anterior fold of the coi’pus callosum is thickest 
 at its abrupt bend, whence it tapers downwards and 
 backwards; its final margin, reaching the anterior crura 
 
69 
 
 of the fornix, throws off to either side a medullary 
 line, which passes between the optic nerves and the 
 lamina cribrosa, and disappears below the obtuse ex- 
 tremity of the middle lobe ; the anterior commissure 
 is placed immediately over this line. Laterally, the 
 extremity of this fold is continuous with the thin me- 
 dullary layer, which supports the convolutions of the 
 internal and under surface of the anterior lobe, and 
 in conjunction with the lamina cribrosa forms the in- 
 ferior wall of the capsule. The concave surface of 
 this fold forms a centre of radiation for the fasciculi 
 of the fore part of the corpus callosum : to it is affixed 
 the anterior extremity of the septum lucidum, the two 
 plates of which enclose a ventricle, allowing an ex- 
 pansion of two short horns at its fore part, and con- 
 tracting it behind to a pointed termination on the 
 lyra. The plates of the septum adhere at the fore 
 part to the edges of a broad furrow in the corpus 
 callosum, in which the inferior raphe is contained ; 
 and behind, to the crura of the fornix. The fasciculi, 
 which radiate from the anterior margin of the corpus 
 callosum, meet the anterior fasciculi of the fibrous 
 cone. Those, which radiate from the anterior fold 
 below this, bend round the obtuse margin of the 
 fibrous cone. Those which are derived from the main 
 portion of the corpus callosum meet at an acute angle, 
 and sometimes directly anastomose with the middle 
 fasciculi of the fibrous cone, and with those derived 
 from the inner and outer walls of the capsule. The 
 apparently structureless medullary substance is con- 
 
70 
 
 traded here to a narrow line, and eventually joins the 
 taenia seinicircularis, and is covered by the gray sub- 
 stance of the extremity of the corpus striatum, and by 
 the epithelium. The deeper fasciculi of either system 
 seem most directly to anastomose, and the inner layer 
 alone of the corpus callosum to pass below, and un- 
 connected with, the fibrous cone. The middle part 
 of the corpus callosum is in connection with the con- 
 volutions of the inner surface of either hemisphere, 
 with those of the vertex, and finally with those of the 
 roof of the fissura Sylvii. 
 
 The fasciculi, which form the posterior margin of 
 the corpus callosum, are arranged in a full roller-like 
 fold : a small portion of this is destined to unite with 
 the fornix and the long convolution, and to extend 
 into the hippocampus. The greater portion expands 
 to form the tapetum of the posterior horn, the fibres 
 of which line the fasciculi of the fibrous cone, crossing 
 the latter at an angle. Sometimes, especially in the 
 neighbourhood of vessels, gray matter is found be- 
 tween the tapetum and the medullary substance, 
 which it covers. The fasciculi of the corpus callosum, 
 which are placed a few lines before its roller-like 
 posterior margin, passing behind the thalamus, form 
 a sort of woven suture with those of the fibrous cone 
 which they cross. The taenia and slender extremity of 
 the inner portion of the corpus striatum are interposed 
 between the posterior edge of the thalamus and the 
 fasciculi last spoken of. The former substance con- 
 tributes a tapetum on the outside of the thalamus ; 
 
71 
 
 elsewhere, in the inferior horn, the tapetum, which is 
 but thin, is derived as above, and its fibres have a 
 similar direction with those of the fibrous cone. The 
 tapetum is thickest about the middle of the roof of the 
 posterior horn. 
 
 The mode of connection between the fasciculi of the 
 vertical and horizontal portions of the nucleus forms 
 an interesting subject of inquiry. It varies seemingly. 
 In the anterior horn, especially near the fold of the 
 corpus callosum, where the fibres of that substance 
 tend towards the obtuse margin of the fibrous cone, 
 the two systems meet abruptly, and in the angle is 
 found an apparently structureless medulla. Behind 
 this the superior layers of the corpus callosum anasto- 
 mose with the fasciculi of the fibrous cone. Again, at 
 the posterior margin of the thalamus, and for a dis- 
 tance of two lines from that body, the fasciculi of each 
 system decussate each other, and are interwoven. 
 Finally, the posterior portion of the corpus callosum 
 is extended as a distinct and separable layer within 
 the expansion of the fibrous cone. 
 
 The two systems now described form the nucleus 
 of the brain. Between this and the convolutions of 
 each hemisphere, however, another structure is found, 
 afterwards more particularly described : it consists but 
 of fasciculi which pass from the centre of any con- 
 volution to others more remote. It is probable that 
 the convolutions receive fibres both from these fas- 
 ciculi and from either portion of the nucleus. 
 
 To prepare a brain for the demonstration of the 
 
72 
 
 horizontal portion of the nucleus, the hemispheres 
 should be removed by an horizontal incision above 
 the corpus callosum, then laid open from below, the 
 floor of the postei’ior horn cut through longitudinally, 
 and that of the inferior horn transversely at its ex- 
 tremity, in order that the alkohol may have free ac- 
 cess to every part. In the subsequent dissection, the 
 convolutions bordering on the posterior fold of the 
 corpus callosum are to be raised by drawing off the 
 covered bands, in the way already described, which 
 operation will expose the course of the fasciculi of the 
 corpus callosum to their destination, as roof and floor 
 of the posterior horn. The incision directed through 
 the floor of the inferior horn is to allow of the eversion 
 of the hippocampus major, and the exposure of its 
 navicular cavity filled with gray matter. Upon the 
 inner surface of the posterior lobe the small posterior 
 fissure is found, next to that of Sylvius the most re- . 
 markable. This fissure is deep ; it extends vertically 
 upwards from the convolution which laps round the 
 posterior fold of the corpus callosum, along the inner 
 surface of the posterior lobe, over the upper margin 
 of the hemisphere, on the summit of which it ter- 
 minates : it thus skirts the inner surface of the posterior 
 horn, and one of its indentings has a corresponding 
 prominence in that cavity. The exterior wall of the 
 lower part of the fissure is carefully to be broken offj 
 in order to expose the fasciculi which surround the 
 posterior horn: it will then be remarked that the fas- 
 ciculi of the under surface of the posterior fold of 
 
the corpus callosum are extended first transversely ; 
 that they are then prolonged into two bands, which 
 extend to the point of the posterior horn, and are 
 joined at their internal concave margin; while, from 
 the extreme anterior margin of the inflected fold 
 fibres are derived, which expand, fan-like, to complete 
 the walls of the posterior horn: with these the posterior 
 crura of the fornix are partly united, which also are 
 extended along the inferior horn, contain gray matter 
 continuous with that of the adjoining convolution, 
 and with it form the hippocampus major. The white 
 matter of the hippocampus thus derived is continuous 
 internally with the taenia hippocampi ; externally is 
 reflected to form the internal layer of the white 
 matter in the internal and inferior convolution of the 
 middle lobe : the layer opposed to this, again, forms 
 the immediately adjoining part of the floor of the in- 
 ferior horn : it follows that, at the meeting of the two 
 layers, this convolution splits in its axis. The gray 
 substance in the hippocampus allows of being rent in 
 its centre, but is very unmanageable. 
 
 The inner surface of the corpus callosum may now 
 be deprived of its epithelium, which may best be 
 done by separating the two layers of the septum lu- 
 cidum below, carrying the rent upwards, and, when 
 it reaches the corpus callosum, inclining it horizon- 
 tally ; the tapetum then readily peels off, and, at the 
 same time, the furrow belonging to the internal raphe 
 is fairly exposed. The I’emoval of the epithelium 
 exposes the tapetum, or lining, of the ventricular 
 
74 
 
 cavity : at the fore part it is necessary to turn aside 
 the posterior extremity of the taenia semicircularis 
 geminum, and the narrow tail of the internal portion 
 of the corpus striatum : finally, the tapetum itself may 
 be raised with the edge of the knife, introduced at the 
 posterior edge of the thalamus, and the posterior di- 
 vergence of the fibrous cone exposed, in like manner 
 as its anterior radiation is exhibited, on the removal 
 of the inner part of the corpus striatum. 
 
 Explanation of the Ninth Plate. 
 
 In order to exhibit the parts represented in this 
 plate, a fresh brain should be treated in the following 
 way : the upper part of the hemispheres should be 
 removed, by horizontal incisions, a little above the 
 corpus callosum ; the brain being then reversed, is to 
 be deprived of the cerebellum, and upon this laid open 
 from below, by means of an incision in the median 
 plane, through the tubercula quadrigemina, the gray 
 substance at the floor of the third ventricle, the 
 infundibulum, the commissura tractuum opticorum, 
 and the commissura mollis : vertical incisions parallel 
 to this, beginning with either posterior crus of the 
 fornix, are to be carried to the point of the posterior 
 horn of either lateral ventricle. The plexus choroides 
 being next removed, the brain is to be hardened in 
 alkohol, then softened in an alkaline solution, and 
 afterwards again hardened. The covered bands are 
 
75 
 
 now to be taken off, so as to give freedom to either 
 extremity of the corpus callosum, and then the island ; 
 the removal of which allows the separated portions to 
 be freely bent away from each other. 
 
 In doing this, it is necessary to cut through the 
 anterior commissure, and to separate from the body 
 of the fornix its anterior crura; the roots of these 
 bodies, extending from the corpora albicantia into 
 the thalami, may be exposed. The narrow end of 
 the anterior fold of the corpus callosum is to be se- 
 parated laterally from its connexion vsdth the outer 
 part of the corpus striatum and the under surface of 
 the capsule. The epithelium is now to be drawn 
 from the under surface of the corpus callosum, the 
 tapetum shown, and the radiation above it of the 
 fibrous cone. 
 
 The present plate is rather a plan than a drawing, 
 designed from separate portions of hardened brains, 
 and contrived so as to show more parts than can well 
 be exhibited, at one view, in an accurate drawing. 
 
 A. A. The anterior, 
 
 B. B. The middle, 
 
 C. C. The posterior lobes of the brain. 
 
 a. A very imperfect representation of the me- 
 dullary process, which extends from the anterior in- 
 flection of the corpus callosum to the under surface of 
 the capsule. 
 
 b. The anterior fold of the corpus callosum, turned 
 forward, so as to show the great divergence of its 
 
76 
 
 fasciculi at this point, and the furrow of the external 
 raphe. 
 
 c. c. c. c. c. Five curved lines, to show the cor- 
 responding points in the fibrous cone, and in the 
 everted fold of the corpus callosum. 
 
 d. A point, at which the fasciculi of the corpus 
 callosum are separated, to show their breadth. 
 
 e. Section of the commissura tractuum opticorum : 
 on the right side, the passage of the tractus opticus to 
 the thalamus is represented. 
 
 f. Section of the anterior commissure. 
 
 g. The foremost fasciculus of the fibrous cone. 
 
 h. The adjoining fasciculi, having an inclination 
 forward. 
 
 i. A point at which the fasciculi of the fibrous cone 
 appear to be continuous with the deeper fasciculi of 
 the corpus callosum ; the latter being exposed by the 
 removal of the tapetum. 
 
 Tc. The right thalamus. 
 
 l. Section of the right crus cerebri*. 
 
 m. The second layer in the thalamus exposed, with 
 the anterior portion of which the root of the anterior 
 crus of the fornix is seen to be continuous. 
 
 n. n n. Different parts of the fornix. 
 
 * Through an inadvertence, the letter I, in this plate, 
 is crossed, so as to represent a t ; but the error is too 
 gross to mislead. 
 
77 
 
 0. 0. Part of the long convolution, which surrounds 
 the corpus callosum : its adhesion to the posterior 
 fold of the latter, and connection with the posterior 
 crus of the fornix, from the general union of which 
 the hippocampus is derived, are seen. 
 
 p. The posterior fold of the corpus callosum, thickest 
 centrally. 
 
 q. Its prolongation into the hippocampus minor, 
 on the right side. 
 
 r. The same, on the left side, cut through, and 
 turned back. 
 
 s. Section of the tapetum, its greater thickness at 
 its middle. 
 
 t. The radiated expansion of the fibrous cone 
 towards the posterior lobe, seen on the partial re- 
 moval of the tapetum. 
 
 u. An imperfect representation of the fasciculi fur- 
 nished to the roof of the inferior hoi’n from the ex- 
 ternal margin of the thalamus. 
 
 7 ). The inner portion of the corpus callosum of the 
 left side. 
 
 TV. The taenia semicircularis geminum, left ante- 
 teriorly in its natural place, behind drawn aside, so 
 as to show its inferior medullary surface, and the 
 fasciculi, which, teeth-like, plunge into the pecten. 
 
 X. A small portion of the fibrous cone, exposed by 
 a partial removal of the taenia semicircularis. 
 
 y. y. The corpus albicans of either side ; the forma- 
 tion of that on the right alone exposed. 
 
78 
 
 z. Section of the tubercula quadrigemina and crura 
 cerebri. 
 
 1.1. The tapetum, extending from the corpus cal- 
 losum and its posterior fold, to form the surface of 
 the posterior horn of the lateral ventricle. 
 
 2. A point, at which the fasciculi of the tapetum are 
 apart, and those of the fibrous cone exposed. 
 
 3. The tapetum of the inferior horn of the lateral 
 ventricle, which is partly derived from the corpus 
 callosum, partly from the taenia, and from the thala- 
 mus. The representation is imperfect. 
 
 XI. 
 
 Of the Fissura Sylvii, of the Striated Body, and of the 
 Medullary Capsule. 
 
 The fissura Sylvii extends, from its commencement 
 below, obliquely upwards and backwards for more 
 than a third of the length of the brain. The boundary 
 of the fissure belonging to the anterior lobe may be 
 termed its roof ; that belonging to the middle lobe its 
 floor ; the roof and the floor meet behind at an acute 
 angle; intermediately they inclose a space, covered 
 with low convolutions, which are surrounded by a 
 gutter-like depression. These low convolutions, which 
 form the island, are placed upon the hamular fasciculi. 
 Below the fissura Sylvii, and parallel with its floor. 
 
79 
 
 extends a linear fissure, frequently four inches long. 
 A section through the hemisphere, taken from the 
 anterior part of the gutter, shows its medulla to be 
 a full inch in thickness. 
 
 For the examination of this surface, it is convenient 
 to remove, by an horizontal incision, beginning about 
 half an inch above the corpus callosum, the upper 
 part of a detached hemisphere ; and, while hardening 
 the remaining part, to keep the fissura Sylvii open 
 by means of portions of cork interposed between its 
 roof and floor. The process of hardening, as already 
 described, having succeeded, the tough and flexible 
 mass is to be so bent, as fully to expand the fissura 
 Sylvii, and to expose the island. Then, on a con- 
 volution of the floor, a superficial rent, parallel to its 
 axis, may be made, and carried towards the gutter 
 surrounding the island ,• in a similar way, from all 
 the convolutions inclosing the fissure, a layer may be 
 peeled, and the rent then carried over the island, 
 which will bring away the greater part of its con- 
 volutions. Finally, a rent may now be carried along 
 the axis to the base of a convolution of the roof; 
 which rent, when directed backward from the base 
 of the convolution across fissure, will raise the long 
 fasciculi extending from the anterior to the middle 
 lobe : these are the hamular fasciculi ; they are better 
 seen when raised in slender filaments. 
 
 The outer portion of the corpus striatum is inclosed 
 in its capsule, which has three surfaces ; an outer and 
 an inner wall, and a floor. 
 
80 
 
 The floor consists of the medulla incognita, of the 
 lamina cribrosa, and of the bases of the convolutions, 
 which are in contact with the root of the olfactory- 
 nerve ; it extends inwards towards the apex of the 
 anterior fold of the corpus callosum, backwards to- 
 wards the posterior margin of the crus cerebri, out- 
 wards to the hamular fasciculi. The floor and outer 
 wall are readily peeled off from the gray matter, when 
 the union of the two portions of the corpus striatum, 
 before the margin of the fibrous cone, may be dis- 
 tinctly seen. If the tractus opticus be raised, and 
 the medulla incognita, along with the lamina cribi’osa, 
 be removed from the crus cerebri, it is easy to follow 
 the anterior commissure, passing through the corpus 
 striatum, above the hamular fasciculi, to its fan-like 
 expansion in the outer wall of the inferior horn, 
 where its fibres meet with the external fasciculi of the 
 fibrous cone. 
 
 The outer wall of the capsule is composed of a 
 portion of the hamular fasciculi. The fasciculi, which 
 pass from the inner and under convolutions of the 
 anterior lobe, near the root of the olfactory nerve, 
 and thence extend across the fissura Sylvii to the 
 prominence forward of the middle lobe, are thus em- 
 ployed : their outer extremity closely blends with the 
 fan-like expansion of the anterior commissure : fine 
 fibres from the latter may be traced to the medulla 
 incognita and to the taenia. 
 
 The fasciculi above specified contain the centre 
 nearly of the radiation of the entire outer wall of the 
 
81 
 
 capsule : here the fasciculation is finer, as well as some- 
 what laminated, which, towards the superior convex 
 mai gin of the gray mass, is coarse. At the upper 
 margin of the outer part of the striated body, the 
 outer and inner walls of the capsule meet at an acute 
 angle, decussate each other, and are interwoven : 
 here, too, the fasciculi of the fibrous cone, and those 
 of the corpus callosum meet, and one general and 
 intricate intermixture of fibres, from all these sources, 
 occurs. In connection with the fasciculi of the fibrous 
 cone, the hamular fasciculi extend as far back as the 
 end of the posterior lobe ; inwards, towards the 
 corpus callosum ; downwards, to the inferior horn of 
 the lateral ventricle. 
 
 Besides what is strictly the outer wall of the capsule, 
 there may be raised, after the general removal of the 
 convolutions, other medullary fasciculi, which have 
 passed from the centre of the base of one convolution 
 to that of another, connecting not merely adjoining, 
 but even remote convolutions : these are especially 
 found within the convolutions of the roof of the fissura 
 Sylvii, whence they pass round the island to convo- 
 lutions in the middle lobe : this structure is probably 
 general, and is probably intended, with the hamular 
 fasciculi, for the common purpose of associating to- 
 gether in action the convolutions of the great divisions 
 of either hemisphere. 
 
 The inner wall of the capsule is composed of the 
 outer surface of the fibrous cone. The substance 
 contained in this capsule is the outer portion of the 
 
 G 
 
82 
 
 corpus striatum, the inner part of which projects un- 
 covered into the lateral ventricle. The outer portion 
 has a broad inferior surface ; above, a sharp falciform 
 margin : before, its extremity is obtuse ; behind, 
 pointed ; its breadth anteriorly, where greatest, is 
 about an inch; its length about three inches; its 
 depth an inch and a half : in an horizontal section its 
 form appears elliptical : its anterior extremity joins 
 the internal portion before the foremost fasciculus of 
 the fibrous cone ; its upper margin is parallel to that 
 of the inner poi’tion, but about two lines lower in the 
 brain ; its posterior extremity occurs about two lines 
 before that of the thalamus. Every where but at its 
 fore part it is shut in by its walls. Anteriorly it is 
 perforated by the anterior commissure ; gives support 
 to the commissura tractuum opticorum ; is continuous 
 with the infundibulum ; and, being prolonged, sur- 
 rounds the anterior crura of the fornix and the 
 corpora albicantia ; overlays the walls of the third 
 ventricle, and unites the thalami, under the form of 
 the commissura mollis. It is a question whether this 
 part has not an epithelium as well as the inner por- 
 tion : but, it may be remarked, that it peels smoothly 
 from the floor and outer walls of its capsule. 
 
 When layer after layer is raised from the outer 
 wall of the capsule, an appearance is met with as if 
 fibres radiated from the upper margin of the gray 
 matter. It would seem, that medullary fibres arise 
 from the whole gray substance, the direction of which 
 is towards its upper margin, where they plunge into 
 
83 
 
 the substance of the inner and outer walls of the 
 capsule. On separating the outer portion of the 
 corpus striatum from the inner wall, a similar ap- 
 pearance is met with ; and, in addition, exceedingly 
 fine fibrils seem to be derived from the fibrous cone, 
 and to enter the gray matter. It is possible, at least 
 sometimes it has appeared to me, that fine medullary 
 fibres are derived from the outer wall likewise, and 
 enter the gray substance. 
 
 The corpus striatum receives its blood-vessels be- 
 low through the lamina cribrosa; above through 
 the pecten. With its developement that of the other 
 parts of the brain is in some measure proportionate. 
 It is the centre of the hemisphere, and this region is 
 remarkable as the seat of the greatest deviations from 
 the natural state in idiotcy and other mental affec- 
 tions. 
 
 Explanation of the Tenth Plate. 
 
 A. B. C. D. Margin of the three lobes of the bram. 
 The island has been removed, and the adjoining con- 
 volutions rent in their axes. The outer wall of the 
 capsule is exposed. 
 
 a. a. a. a. Rent surfaces of convolutions. 
 
 h. Hamular fasciculi. 
 
 c. d. e. f. Their radiation towards the different 
 parts of the brain. 
 
 g. Outer wall of the capsule. 
 
 G 2 
 
84 
 
 Of the Medulla Oblongata, and of the superior, lateral, 
 and inferior Crura of the Cerebellum, by Professor 
 Reil. Archiven fur die Physiologie. Neunter band, 
 p. 485—524. 
 
 XII. 
 
 Of the Medulla Oblongata, and the Floor of the 
 Fourth Ventricle. 
 
 It is difficult to define the exact point, at which the 
 medulla spinalis ends and the medulla oblongata 
 begins; as the latter approaches the former, it gradually 
 assumes a similar structure with it. The medulla 
 oblongata consists, on the fore part, of the pyramids, 
 of two considerable medullary processes, external to 
 these, one on either side, to which the corpora olivaria 
 belong, of the corpora restiformia, and, finally, of 
 two slender chords which are in apposition at the 
 median plane behind. 
 
 The pyramids are the most distinctly fasciculated 
 among the parts of the medulla oblongata: in their 
 course downwards they become narrower, and, finally, 
 dip inwards from the surface to their decussation, which 
 takes place in the central gray matter. It is not known 
 whether they arise at this point, or are continued down- 
 wards into the substance of the medulla spinalis. In 
 
85 
 
 their ascent they make a distinct channel in the corpora 
 olivaria, and are internally in mutual contact : towards 
 the posterior margin of the annular protuberance, 
 they separate from each other and from the adjoining 
 bodies, and plunge, as separate cylinders, into that 
 substance : all their fasciculi, however, do not appear 
 to pass through the annular protuberance; some ascend 
 behind it, and join with those of the fillet. To under- 
 stand the interweaving which takes place at a right 
 angle between the fibres of the pyramids and those of 
 the lateral peduncles of the cerebellum, it may be con- 
 venient to divide through the calamus scriptorius, and 
 in the median plane, the medulla oblongata and the 
 annular pi’otuberance, as far as to the under layer of 
 the latter. From the rent surfaces the different layers 
 may be readily raised. The annular protuberance is 
 formed by the interweaving of the lateral peduncles 
 of the cerebellum with the fasciculi of the pyramids, 
 and all the other portions of the medulla oblongata, 
 as well as the remaining peduncles of the cerebellum, 
 are placed behind this mass. The corpora olivaria, on 
 the removal of the pyramids, are somewhat cordiform ; 
 they resemble the ciliary bodies, and are connected 
 with the grey matter of either half of the medulla ob- 
 longata in a manner analogous to the connection of 
 the corpora geniculata with the thalami. The portions 
 of the medulla oblongata, of which these bodies form 
 a part, may be traced downwards as far as the de- 
 cussation of the pyramids, and upwards behind the 
 corpora olivaria to constitute part of the cylinder of 
 
86 
 
 either crus cerebri. Sometimes a fasciculus, derived from 
 the lower part of the pyramid, passes round the outer 
 margin of the corpora olivaria, and then rejoins the 
 pyramid. The third pair of eminences are the posterior 
 peduncles of the cerebellum ; the fourth and slightest 
 are in contact for some extent, but afterwards are in- 
 clined away from each other to expose the lozenge- 
 shaped field of the fourth ventricle ; they are enlarged 
 at the angle where the divergence begins. 
 
 The lozenge-shaped field thus angularly commen- 
 cing below, contracts above, to a point at which the 
 aqueduct of Sylvius or iter ad quartum ventriculum 
 opens ; its margins are made out by the peduncles of 
 the cerebellum. It contains, as in a basin, grey matter, 
 derived from that in the spinal chord, only broadei’^ 
 and proportionate to the increase of white matter. 
 Grey matter ascends uninterruptedly in the axis of the 
 nervous system, chord-like below, a chain of ganglions 
 above, the tubercula quadrigemina, the thalami, the 
 corpora striata. 
 
 The gray substance of the lozenge resembles that 
 of the tubercula and thalami ; it is paler and firmer 
 than that of the corpus striatum, and is disposed in 
 fibres, which run parallel with its median furrow, the 
 calamus scriptorius. Where the lateral and posterior 
 peduncles of the cerebellum meet at the broadest part 
 of the lozenge, the small triangular chamber exists, 
 into the grey substance contained in which the roots 
 of the portio dura and of the fifth sink, and perhaps 
 those of the eighth ; whether they go beyond it is pro- 
 
87 
 
 blematical. To me it seems that the origins of nerves 
 are uniformly in grey matter; that the optic nerve 
 rises from the corpus geniculatum, the third from the 
 black matter, the fifth, seventh, and eighth, from the 
 chamber just described, and the spinal nerves from the 
 grey matter in the axis of the spinal chord. 
 
 Two cylindrical fasciculi ascend from as low down 
 as the crossing of the pyramids, one on either side of 
 the central groove of the lozenge : these are half 
 medullary, and simply covered with epithelium ; they 
 are broadest in the centre of the lozenge, and are con- 
 tracted below as well as above, where they join the 
 thalami above the ansa of the anterior peduncles of 
 the cerebellum. 
 
 One other layer, the vertical fasciculi, composed not 
 of nervous matter alone, but of cellular membrane 
 likewise, and vessels in unusual proportion, as may be 
 conjectured from its toughness, extends from behind 
 the pyramids, behind the upper transverse fibres of 
 the annular protuberance, and below the ansa of the 
 anterior peduncles of the cerebellum, to the grey sub- 
 stance which is found between the crura cerebri, ex- 
 tending beyond the corpora albicantia, thus building 
 tile floor of the third ventricle, and becoming con- 
 tinuous with the infundibulum. The fibres of this 
 stratum seem in some degree to decussate each other. 
 
88 
 
 XIII. 
 
 Of ike iriferior Peduncles of the Cerehelhm. 
 
 The lobes and lobules of the cerebellum are placed 
 upon a nucleus, which has been described as formed 
 of an extension of its peduncles, and contains the 
 ciliary bodies. Of these peduncles, the lateral alone 
 are confined to the cerebellum ; each of these meets 
 its fellow anteriorly in the annular protuberance, be- 
 hind, in the vermiform processes. The lateral pe- 
 duncles are the largest, and are cylindrical ; the in- 
 ferior are cylindrical, but of less magnitude ; the su- 
 perior are broad and flattened. 
 
 The inferior peduncles, viewed as parts of the 
 medulla oblongata, are distinguished by a more re- 
 markable line of separation from the corpora olivaria 
 than fi’om the fasciculi behind them. Between the 
 three substances just mentioned, the chords of gray 
 matter derived from either half of the spinal chord 
 emerge upon the lozenge- shaped field. Where the 
 inferior peduncles bend away from the medulla ob- 
 longata to join the cerebellum, they are in form oval, 
 being flattened before and behind. At this part the 
 - principal root of the flock passes round the inferior 
 peduncle in its course to reach the external margin 
 of the superior peduncle; and the surface is overlaid 
 
89 
 
 with the root of the auditory nerve, and the transverse 
 medullary fibres of the calamus scriptorius. 
 
 At the outer margin of the superior peduncle an 
 oblong elevation exists, which forms the outer wall 
 of the nidus, and is generally taken for the inferior 
 peduncle. Now if the stem of the flock be removed 
 which passes over this surface, the true course of the 
 inferior peduncle may be seen, and the elevation in 
 question is found to be continuous with the medulla 
 of the lateral peduncle. On raising this external 
 medullary layer the prominence will be found to result 
 from and to have contained a portion of the ciliary 
 body. The inferior peduncle now passes between the 
 superior and lateral peduncles; with the lateral pe- 
 duncle throws itself over the root of the superior 
 peduncle and of the adjoining velum, and then passes 
 to unite with its fellow in the superior vermiform 
 process. As a line of distinction between the lateral 
 and inferior peduncles, an angle of the chamber before 
 alluded to is continued some little v/ay in their in- 
 terval. From the trunk of the inferior peduncle its 
 medullary fibres pass backward, the upper fasciculi 
 form the roof of the capsule of the corpus ciliare, 
 the lower pass in part below it. 
 
 The corpus ciliare in either hemisphere may be 
 described as inclosed in a capsule formed by the fas- 
 ciculi of the peduncles, v.?hich surround it. In form 
 it is flattened and triangular, with blunted corners, of 
 which one looks forwards tow'ards the prominence 
 above described ; its base is turned towards the 
 
90 
 
 posterior lobe. The outside of the capsule is bounded 
 by the lateral peduncle, the inside borders on the 
 vermiform process, the roof is formed by the posterior 
 peduncle, the floor by the superior and some fasciculi 
 of the inferior. The corpus ciliare is easily raised 
 from this capsule. It allows of being unfolded into 
 lobules which seem directed from before backward. 
 Probably many fasciculi from the anterior peduncle 
 pass into this substance, and lose themselves there. Its 
 substance is permeated by many vessels accompanied 
 probably with pia mater. Some of these vessels enter by 
 a cribriform surface between the superior peduncle and 
 the roller-like eminence of the lateral peduncle *. To 
 these vessels may be ascribed the arborescent tubes 
 which extend from before backwards in the ciliary 
 body f. 
 
 In preparing a cerebellum for exhibiting the pre- 
 
 * Laminae cribrosae are found besides between the crura 
 cerebri and the fillets, round the corpora geniculata in- 
 terna, between the corpora albicantia, crura cerebri, and 
 anterior margin of the annular protuberance, and in the 
 fossa on the outside of the corpora olivaria. 
 
 f The blood-vessels below the taenia semicircularis 
 geminum lie in channels which have red walls, probably 
 from the transudation of the blood. To the same cause 
 may be, perhaps, attributed the occasional red colour of 
 the gray substance, as in the thalami, when the alkohol 
 has not thoroughly penetrated it. 
 
91 
 
 ceding circumstances, the square lobe is to be broken 
 off, the anterior peduncle largely exposed by pressing 
 aside the other two peduncles, which cross over it. 
 The biventral and thin lobes are then to be removed, 
 the almond-like lobes broken off from their stems, the 
 flocks raised from without inwards, and the roots of 
 the auditory nerves peeled back from the inferior 
 peduncles: it only remains to follow the course of 
 the several peduncles now distinctly entering the cere- 
 bellum, and finally to raise the corpus ciliare with 
 care from its capsule. 
 
 XIV. 
 
 Of the lateral Peduncles. 
 
 The lateral peduncles, with their continuations, 
 form a ring encircling the other parts of the cere- 
 bellum. This ring is completed on the fore part by 
 the annular protuberance, in which the substance of 
 the peduncles is spread out in strong and coarse 
 fasciculi, so disposed as not to preserve an uniform 
 distance from the surface, but now to approach it, 
 now to recede from it, and in parts to cross each 
 other. The upper and posterior surface of the annular 
 protuberance, stripped of the layers which otherwise 
 cover it, is found to be convex, from above down- 
 wards; and the superincumbent mass is proportionately 
 thinner at its centre. The intervals between the 
 transverse fasciculi of the lateral peduncles, and the 
 
92 
 
 ascending fibres of the pyramids, which are inter- 
 woven with them at right angles, are filled with gray 
 substance; the latter seems to have more to do with 
 the cross fibres than with those of the pyramids, and is 
 the principal channel of the blood-vessels. Some long 
 fasciculi, derived from the pyramids, ascend above the 
 hindmost transverse fibres to join the fillets : on this 
 account the upper layer of the annular protuberance 
 may be described as composed of longitudinal fibres. 
 After the first layer of cross fibres, which is of tolerable 
 thickness, a bi’oad set of longitudinal fasciculi follow; 
 then transverse, then longitudinal fasciculi; again 
 transverse, and again longitudinal fasciculi, which last 
 are supported on the thickest and convex stratum of 
 transverse fibres, which form the under surface of 
 the annular protuberance. The longitudinal fasciculi, 
 which are nearest to the median plane, are likewise 
 nearest to the under surface, and pursue a straight 
 course with the pyramids : those which occur next 
 are nearer the upper surface, and are inclined out- 
 wai’ds from the pyramids. Just in the median plane, 
 transverse fibres and gray substance alone are found. 
 Whether any connection exist between the two sets of 
 fibres above described is uncertain. A blind de- 
 pression, out of which the third nerves seem to emerge, 
 exists between the crura cerebri and the anterior and 
 upper margin of the annular protuberance : a similar 
 pit exists at the lower margin of the latter. Where 
 the fasciculi of the crura cerebri join the annular pro- 
 tuberance, their margins are reciprocally indented. 
 
93 
 
 The lateral peduncles, followed backward along 
 the horizontal fissure, internally divide into an upper 
 and an under layer, the fibres of which in part pass 
 inwards towards the vermiform processes, in part 
 radiate backwards to be distributed to the posterior 
 lobes of the cerebellum. On this account rents of 
 these lobes break deep into the substance of the lateral 
 peduncles, whereas the upper and under lobes break 
 superficially off, leaving ridges upon the surface of 
 the peduncle. The fasciculation of the peduncle is 
 finer when within the cerebellum : very likely there 
 is no substance intermediate between the peduncle 
 and the lobes. Under the anterior and external 
 angle of the square lobe a centre exists, whence the 
 fasciculi of the peduncle spread out, and in a curvi- 
 linear direction, tend towards the vermiform processes. 
 Upon the under surface the flock must he taken off, 
 to show the apposition of the lateral to the superior 
 peduncle. The former throws a circular layer round 
 the bend of the inferior peduncle to join the superior ; 
 this contains the projecting outer margin of the 
 anterior extremity of the ciliary body. I'he lateral 
 and inferior peduncles throw themselves inwards.over 
 the superior, to unite with their fellows in the superior 
 vermiform process. Below, the lateral peduncle ad- 
 heres to the flock, which is inclined round the nidus, 
 to reach the stem of the pyramid : then follow the 
 stems of the biventral and slender lobes ; and the re- 
 maining portion of the lateral peduncle radiates into 
 the under and posterior lobe. 
 
94 
 
 In preparing a cerebellum for the demonstration 
 of this part, the square lobe must be broken away, 
 above ; the flocks with their stems, the biventral, and 
 the slender lobes, below ; the almond-like lobes must be 
 drawn off from their stems in a direction from below 
 upwards ; the posterior crura fairly exposed at their 
 bend, and the apex of the ciliary body denuded. 
 
 XV. 
 
 Of the superior Peduncles^ the anterior Medullary 
 Velum, and the Fillets. 
 
 Either fillet may be traced as far as the inferior 
 margin of the annular protuberance : at this point it 
 lies betwixt the pyramids and the upper margin of the 
 corpus olivare, and is continuous with that layer of 
 the former which passes behind the superior transverse 
 fibres of the annular protuberance, and with the fas- 
 ciculi derived from the summit of the latter. Inwards, 
 the fillet is bounded by the vertical fasciculi already 
 described as continued to the infundibulum : outwards, 
 it extends to the point at which the fifth and seventh 
 nerves dip in. Just before it reaches this level, the 
 fillet divides ; one part is directed forwards, imme- 
 diately above the fibres of the pyramid, and passes 
 below the black substance; the other, having passed 
 below the roots of the fifth and seventh nerves, then 
 strikes upwards, and emerges between the anterior 
 
95 
 
 and lateral peduncles of the cerebellum, and the crura 
 cerebri ; is then obliquely bent over the superior pe- 
 duncle, at the outside of the inferior tubercle. This 
 portion, again, of the fillet divides : one part, the ex- 
 ternal, attaches itself to the column of fasciculi which 
 ascends behind the annular protuberance, and passing 
 below the corpus geniculatum, joins apparently the 
 fibrous cone. The internal part inclines inwards, and 
 expands below the tubercula, principally the superior, 
 so as to join its fellow of the opposite side in the median 
 plane. This inner subdivision of the fillet forms the 
 roof of the iter ad quartum ventriculum ; and its upper 
 central fibres are seen through their epithelium, at 
 the interval between the superior tubercles. The 
 transverse medullary fibres of the posterior com- 
 missure are, like the preceding, continuations of this 
 inner subdivision of the fillet. On raising the convex 
 surfaces of the tubercula, and following this process of 
 the fillet, a gray and vascular prominence is found, 
 corresponding with each inferior tubercle, disposed 
 transversely, having an obtuse termination outwards, 
 and narrowing inwards. At the inferior margin of 
 each prominence, fibres of the fillet pass across; per- 
 haps they penetrate below it likewise. 
 
 The fasciculi of the fillet are parallel to its course. 
 The anterior peduncle of the cerebellum is so slightly 
 attached to it, that, on the removal of the epithelium, 
 a probe may readily be passed between the two former 
 substances. 
 
 Eor the demonstration of this part, a half-hardened 
 
9G 
 
 brain is to be selected, and the epithelium removed 
 from the fillet, and from the anterior peduncle of the 
 cerebellum. The fillet is then to be followed in its 
 upward course ; the convex surfaces of the tubercula 
 raised from it, as far as the median plane; and thus 
 the inner subdivision exposed. In following the outer 
 portion, it is necessary to raise the tractus opticus, 
 with its ganglion, and then the posterior margin of 
 the thalamus. In tracing the fillet downwards, the 
 lateral peduncle of the cerebellum is to be pressed 
 away from it to some depth ; a rent then carried 
 along the calamus scriptorius through to the upper 
 transverse fibres of the annular protuberance; and 
 the mass of longitudinal fasciculi behind them raised 
 from within outwards ; between which and the trans- 
 verse fibres the fillet descends; Lastly, the fillet may 
 be cut across, and its anterior surface exposed. 
 
 The anterior peduncles of the cerebellum are flat, 
 and most resemble in structure the fillets, or the 
 fornix. Like the former, they extend between por- 
 tions of gray matter, viz. between the gray matter of 
 the ciliary body and the cylinder of the crus ; as the 
 fillets extend between the thalami and the cylinders. 
 Like the fornix, their fibres are flax-like, delicate, 
 and distinct; they decussate each other laterally, and 
 thus doubly unite the cerebrum and cerebellum. The 
 general direction of their fibres is longitudinal. 
 
 It may be convenient to divide each of them into a 
 body and two extremities : the body, or exposed part, 
 is entirely covered with epithelium, and in addition, 
 
97 
 
 with a thin layer of gray matter on its under surface. 
 Between the bodies of either is expanded the anterior 
 medullary velum; a substance consisting of fibres, 
 which run parallel with those of the anterior pedun- 
 cles, and finally pass between the upper and under 
 vermiform processes to complete their nucleus. Either 
 surface of the velum is covered with epithelium. The 
 upper surface is sometimes, at an early period, me- 
 dullary; but is, in most instances, covered with a 
 transversely furrowed layer of gray matter. In the 
 latter case the first lobule of the superior vermiform 
 process is either wholly continuous with the velum, or 
 its base alone, or, perhaps, merely its margins, by 
 which means a canal is enclosed, running backwards 
 between the velum and this lobule*. A small process 
 extends some way upon the velum, derived firom the 
 centre of the posterior tubercles. In the sheep’s brain, 
 a packet of fibres passes from one peduncle to the op- 
 posite, immediately behind the tubei’cles; and another 
 cross band is formed at the further margin by the an- 
 terior and posterior peduncles together ; whence results 
 an oval, in which the anterior velum is expanded. In 
 the human brain more or less of the same structure 
 exists : there, too, fasciculi, derived from the entire 
 nucleus of the cerebellum, pass forward and upward 
 in the form of anterior peduncles and medullary velum. 
 
 * Malacarne, Nuova Exposizione della vera Struttura 
 del Cerveletto Umano. Torino, 1776. p. 108. 
 
 H 
 
98 
 
 enter the cylinder of the crns cerebri, on either side 
 of the aqueduct of Sylvius, and below it blend to- 
 gether. 
 
 The anterior extremity of the peduncle crosses be- 
 low the fillet, inclines rather downwards and inwards, 
 forms the anterior margin of the lozenge-like field, 
 completing, in connection with its body and the me- 
 dullary velum, the sloping I'oof of the fourth ventricle. 
 In the angle at which the roof meets the inclined 
 floor of the ventricle, a stripe of black matter is seen 
 through the epithelium covering it. Here, and in 
 the crus cerebri alone, before the annular protu- 
 berance, black matter is met with ; and at both points 
 it seems to belong to the superior peduncles of the 
 cerebellum: sometimes the black matter is wanting, 
 and in its place the nervous matter is stained red 
 with blood. From the median furrow of the lozenge, 
 delicate medullary fasciculi emerge, which run ob- 
 liquely above the ascending processes formerly de- 
 scribed, above the black substance again, and attach 
 themselves to the inner margin of the superior pe- 
 duncles. 
 
 The peduncles now plunge downwards, forwards, 
 and inwards, into the cylinder, having, above, the tu- 
 beicula quadrigemina, above and without, the fillets, 
 within, the vertical fasciculi : below the latter they 
 unite by means of an ansa, which is several lines in 
 thickness, and forms the upper wall of the foramen 
 caBcum : it is a question whether a complete con- 
 tinuity or anastomosis occurs here. Above this ansa 
 
99 
 
 then, as has been already mentioned, is the course 
 of the cylindrical fasciculi: below it, that of the 
 vertical fasciculi ; some of the component fibres of 
 the cylinder pass right through the substance of the 
 anterior peduncles. The anterior peduncles finally 
 radiate forward, and surround a mass of gray sub- 
 stance in the inner and posterior part of the thala- 
 mus, which lies before the ansa, and behind the root 
 of the fornix. 
 
 The posterior extremity of either superior peduncle 
 extends below the roller-like substance into an hemi- 
 sphere of the cerebellum. It has sometimes appeared 
 to me, particularly in the bi’ains of sheep, that from 
 the chamber formerly alluded to a process passes 
 below the inferior peduncle to unite with the superior 
 just before it disappears from the surface. Along the 
 depressed line, where the superior peduncle and roUer- 
 like substance meet, a lamina cribrosa occurs, through 
 which vessels pass to the ciliary body: the inner margin 
 of the anterior extremity of the ciliary body peeps out 
 at this interval likewise. The superior peduncle, which 
 is contracted at the point where it disappears, now 
 extends directly backwards ; laterally it spreads itself, 
 and divides into packets; appears to enclose some 
 portions of the ciliary body, to penetrate, and even to 
 terminate in them. The greater part of the ciliary 
 body lies, however, above the superior peduncle, the 
 outer and anterior prominence alone being fairly 
 below it. On the whole, the connection of the su- 
 perior and infei’ior peduncles with the ciliary body, 
 
 H 2 
 
100 
 
 anil the manner, in which the superior peduncles 
 terminate, is so confused and intricate, that I cannot 
 venture to speak positively respecting its structure. 
 Some elucidation of these points may be hoped from 
 successful injections of the part. 
 
 In preparing for a demonstration of these cir- 
 cumstances, it is convenient to break away the square 
 lobes from the cerebellum ; to strip the fillets, and the 
 bodies of the supei'ior peduncles, of epithelium ; to 
 divide the vermiform processes in the median plane ; 
 to raise the roller-like substance from the superior 
 peduncles, and to turn aside the inferior and lateral 
 peduncles, with the ciliary bodies adhering to them. 
 Then the caps of the tubercula quadrigemina may be 
 pressed off, to expose the radiation of either fillet, the 
 fillet itself I’aised from the outer surface of the superior 
 peduncle, the inner surface of which is to be denuded, 
 and the aqueduct of Sylvius laid open, to show the 
 ansa. The cylindrical fasciculi may finally be raised, 
 and either superior peduncle itself turned forward, that 
 its inferior surface may be seen. 
 
 XVI. 
 
 Of the Tuhercula Quadrigemina, and Thalami. 
 
 As the dissection of the brain proceeds, these bodies 
 lose their character of distinct organs. The tubercula 
 quadrigemina have four round caps of gray matter, 
 
101 
 
 which arejplaced on the radiation of the fillet : before 
 and behind the four tubercles, and below the anterior 
 pair, that radiation may be traced ; on the one hand 
 including the posterior commissure, on the other, 
 fibres, which pass to the frasnulum. The substance of 
 the posterior tubercles extends the deepest; so that 
 these remain, after the exposure of the radiation of 
 the fillet. 
 
 Laterally the tubercles are covered by the posterior 
 extremity of the thalami, and they have processes 
 which plunge anteriorly and laterally into those bodies. 
 The fillet ascends underneath the process of the pos- 
 terior tubercle; then underneath the corpus geni- 
 culatum it extends into the thalamus, expands, and 
 blends with the production of the corpus geniculatum 
 and the fillet : the three substances together pass on 
 to join the fibrous cone. Yet, must it not be ex- 
 pected, that in the tubercula, and still less in the 
 thalami, the different layers lie distinct: they are 
 rather fused, and blended in one mass. From the 
 processes of the posterior tubercles, fibres seem to 
 proceed, in a curvilinear direction, over the corpora 
 geniculata to the posterior margins of the thalami. 
 
 The transverse fibres of the posterior commissure 
 are individually distinct behind ; but apparently, on 
 the fore part, connected into one bundle by epithe- 
 lium. Above it is placed the pineal gland, connected 
 by four peduncles to its anterior and posterior sur- 
 faces. The posterior commissure is prolonged in a 
 medullary band along the upper and inner margin of 
 
102 
 
 the thalami. Another process of the posterior com- 
 missure passes transversely across the lateral processes 
 of the anterior tubercles ; and a third seems to de- 
 scend vertically in the thalamus to the anterior and 
 outer margin of the same. At least, I have often 
 found a delicate nerve, of the thickness of an horse- 
 hair, taking this course. 
 
 At the floor of the aquseductus Sylvii the cylindrical 
 fasciculi are placed ; below these, the ansa of the an- 
 terior peduncles of the cerebellum ; and then the re- 
 maining mass of the crus cerebri. 
 
 The thalami have each a cap, v/hich is superficially 
 covered with medulla, and may be pressed off* from the 
 upper margin of the wall of the third ventricle, and 
 from the corpora geniculata ; behind, where it is of some- 
 what less breadth, it divides into two projections. The 
 posterior obtuse projection, which is fully seen on the 
 removal of the tractus opticus, and lies immediately 
 below its ganglion, forms, in common with the taenia 
 semicircularis and some fibres of the corpus callosum, 
 the tapetum of the inferior horn, and blends with the 
 radiation of the fibrous cone and anterior commissure. 
 The other inclines round the crus cerebri, and is pro- 
 longed into the tractus opticus. 
 
 The tractus optici arise in part from thin medullary 
 plates, which cover the surface of the thalami, in part 
 by roots, which emerge below the inferior margin of 
 the thalamus, and partly by medullary fibres derived 
 from the corpus geniculatum internum : upon either 
 tractus is found a corpus geniculatum externum. The 
 
under surface and concave margin of the tractus are 
 unattached; the upper surface is attached by mem- 
 brane to the crus cerebri, and the outer margin seems 
 to cohere with the gray substance of the corpus stria- 
 tum, and to have vessels which pass above and below 
 the medulla incognita, with something of the disposi- 
 tion of meseraic vessels. Their commissure adheres 
 above to a layer of gray substance, which extends to 
 the infundibulum from the floor of the third ventricle. 
 In the caps of the thalami, the roots of the anterior 
 crura of the fornix arise. 
 
 The substance below these caps blends with the pro- 
 cesses of the tubercula quadrigemina, with the radia- 
 tion of the corpora geniculata, and with that of the su- 
 perior peduncles of the cerebellum. Before the ansa of 
 the latter, the gray mass already spoken of at the back 
 part of either thalamus is found. The corpora genicu- 
 lata of the thalami are globular, and gray behind, an- 
 teriorly medullary, and expand themselves over the 
 crura cerebri, especially along their outer margin. At 
 the outer margin of the thalami these various struc- 
 tures blend in the pecten, which is thus a texture 
 woven of the crura cerebri and thalami. The inner 
 surfaces of the latter are united by the commissura 
 mollis, and by the substance of the floor of the third 
 ventricle, which extends from the infundibulum to the 
 aquaeductus Sylvii. 
 
i04 
 
 Explanation of the Eleventh Plate. 
 
 In preparing for this demonstration, the greater part 
 of the hemispheres of the cerebrum may be removed, 
 care being taken to leave the corpora striata and optic 
 thalami uninjured. It will be better to begin with cut- 
 ting the corpus callosum through longitudinally as far 
 as its anterior fold, leaving the latter entire to assist in 
 holding together the corpora striata on the forepart. 
 
 a. a. The posterior margin of the hemispheres of 
 the cerebellum, consisting internally of the under and 
 posterioi’, externally of the upper and posterior lobe. 
 
 b. The posterior, or purse-like fissure, in which 
 the last lobule of the superior vermiform process 
 remains unremoved. 
 
 c. The lateral peduncle of the right side of the 
 cerebellum exposed by the removal of nearly the 
 whole of the square lobe: the coarse ridges, with 
 which the lobules of the latter were articulated, are 
 seen to pass from the peduncle, in a curvilinear and 
 somewhat divergent course towards the superior 
 vermiform process. 
 
 d. A small portion of the square lobe unremoved. 
 
 . e. The right anterior peduncle of the cerebellum, 
 covered with its epithelium, and emerging from below 
 the lateral peduncle, 
 
 f. The fillet on the right side, which dips in between 
 the anterior and lateral peduncles of the cerebellum 
 and the crus cerebri, to reach the floor of the fourth 
 ventricle. 
 
105 
 
 The crus cerebri, and its deriticulation with the 
 lateral peduncle of the cerebellum, or with the anterior 
 margin of the annular protuberance. This appearance 
 is better seen on the opposite side. 
 
 h. A portion of the corpus callosum pressed aside. 
 The tail-like pi’olongation of the inner part of the 
 corpus striatum is broken off, so as to expose the 
 decussation of the fibres of the two systems of the 
 nucleus at this point. 
 
 i. i. The tubercula quadrigemina of the right side. 
 
 h. The coi'pus geniculatum internum. Above this 
 
 the processes of the upper, and below the processes of 
 the under tubercula enter the thalamus. 
 
 l. The thalamus nervi optici of the right side. 
 
 m. The anterior obtuse extremity of the inner por- 
 tion of the corpus striatum : its inner margin is with 
 the tsenia pressed aside. 
 
 n. The concave surface of the anterior fold of the 
 corpus callosum. The epithelium is removed, ex- 
 cepting near the crura of the fornix. 
 
 0 , A section of the anterior crura of the fornix, be- 
 tw'een which the central part of the anterior commis- 
 sure is seen. 
 
 yj. The medullary nucleus of the vermiform pro- 
 cesses, which, with the anterior medullary velum, is 
 interposed between the anterior peduncles of the cere- 
 bellum : its fibres are disposed like those of the 
 adjoining parts. 
 
 q. The anterior medullary velum, stripped of its 
 epithelium and grey surface; at its junction with 
 the nucleus it is narrowed. The right half of the fraenu- 
 
106 
 
 him of the tubercula quadrigemina is left attached 
 to it. 
 
 r. r. The left superior peduncle of the cerebellum, 
 appearing from below the fillet: it is slightly con- 
 tracted, where the lateral and inferior peduncles 
 cross it : in its progress backward it partly perforates 
 the corpus ciliare, and in part passes below it ; as the 
 inferior above it. 
 
 s. The inferior peduncle of the cerebellum de- 
 tached and thrown outwards: it is seen to emerge 
 from between the lateral and superior peduncles. 
 
 L The lateral peduncle : where it joins the former, 
 a small chamber is left filled with gray matter, from 
 the lozenge-shaped floor of the fourth ventricle, in 
 which the roots of the fifth and seventh nerves are 
 found. 
 
 u. The crus cei'ebri. 
 
 V. w. X. y. The fillet, v. Its fasciculi emerging be- 
 tween the peduncles of the cerebellum and the crus 
 cerebri, pursuing, on the whole, a direction similar to 
 the latter, iw. That portion of its fasciculi, which 
 passes below the tubercula quadrigemina to become 
 continuous with the corresponding portion of the 
 opposite fillet : at the same time the epithelium is re- 
 moved from the inferior tubercle of the left side, 
 which consists of a nodule of gray matter united to 
 its fellow by medullary fibres ; a few fibres of the fillet 
 ai’e seen to pass below this body to the frmnulum. 
 Between the anterior pair of tubercles is a triangular 
 surface, occupied likewise by fibres of the fillet, pass- 
 ing towards the median plane, which are seen indi- 
 
107 
 
 stinctly through their epithelium. Above these is the 
 posterior commissure, which, when seen from behind, 
 is transversely fasciculated. The pineal gland is here 
 removed. 
 
 X, y. The expansion of the fillet in the thalamus, 
 the globular upper part of which has been broken off, 
 from within outwards : these fibres of the fillet blend 
 with the mass of the thalamus, y. Section of the root 
 of the anterior crus of the fornix. 
 
108 
 
 Of the anterior Commissure m the Brain, hy Professor 
 Beil. Arcliiven fur die Physiologie. Eilfter band, 
 
 p. 89 — loo. 
 
 XVII. 
 
 The anterior commissure may be divided into a 
 body and two extremities. The body is cylindrical, 
 and at least twice as large as an optic nerve ; but its 
 bulk varies, like that of all the parts in the brain which 
 resemble nerves. The anterior commissure consists of 
 fasciculi, of the finest fibrils, which admit of ready 
 separation, when the delicate membrane which invests 
 each and all is divided. The cellular sheath of the com- 
 missure seems derived from the floor of the third ven- 
 tricle, and is not dispensed with till the radiated dis- 
 position of the extremities of the commissure begins. 
 
 The anterior commissure extends transversely across 
 the brain, from the middle lobe of the one side to that 
 of the opposite. The central part, corresponding with 
 the interval between the anterior crura of the fornix, 
 is unattached behind: to its anterior and convex 
 margin the septum lucidura is affixed : before it the 
 fillet of the lamina cribrosa ascends to reach the septum : 
 the fillet of the one side is tinited to its fellow by a 
 delicate membrane, which lies before the anterior 
 
109 
 
 commissure, and adheres to the upper margin of the 
 commissura tractuum opticorum. Between the fillets 
 of the lamina cribrosa and the crura of the fornix the 
 anterior commissure exteilds on either side, through 
 an oval hole, into the corpus striatum : its course is 
 by the anterior extremity of the thalamus, between this 
 and the posterior margin of the inner portion of cor- 
 pus striatum, and along the neck between both, in 
 which the taenia inclines downwards. 
 
 Centrally the anterior commissure is raised a little, 
 and somewhat inclined backwards; then plunging 
 laterally into the gray mass of the inner part of the 
 corpus striatum, it passes close below the first fasci- 
 culus of the fibrous cone, or even sometimes is enclosed 
 between its foremost fasciculi. In its course through 
 the outer portion of the corpus striatum it lies about 
 three to four lines above the lamina cribrosa, is ex- 
 tended horizontally in a curvilinear direction, concen- 
 tric with that of the tractus onticus, then is inclined 
 somewhat downward towards the base of the middle 
 lobe, then is directed backv/ards below the posterior 
 extremity of the hamular fasciculi in the entrance of 
 the fissura Sylvii, to the point whence its extremity 
 radiates : when raised, it leaves for this extent a 
 distinct and smooth canal. 
 
 The divergent fibres of the commissure are attached 
 to the inner surface of the hamular fasciculi, pass with 
 these to the roof of the inferior horn, and even to the 
 posterior lobe, blending with the general radiation in 
 these parts. Blood-vessels perforate the lamina cribrosa 
 
no 
 
 in the course of the anterior commissure, and encircle 
 its body, particularly near where the divergence of its 
 fibres begins. 
 
 In sheep, the anterior commissure, as if composed 
 of two cylinders in apposition, divides at either end 
 into an anterior and posterior branch : the anterior 
 branch bends itself forward at the foremost fasciculus 
 of the fibrous cone towards the processus mammillaris 
 and its outer wall, and is lost where the latter meets 
 by a narrow opening the anterior horn, in radiated 
 fibres which surround this opening. The posterior 
 branch, on either side, is much thinner, and passes 
 along the isthmus between the corpora striata and 
 thalami in which the taenia lies : ip the hare a similar 
 organization is seen. 
 
 In preparing these parts for demonstration, the 
 hemispheres are to be cut away above the corpus cal- 
 losum, the brain hardened, and the hamular fasciculi 
 in the fissure of Sylvius carefully exposed. The brain 
 being then reversed, the floor of the inferior horn is 
 to be removed, the hamular fasciculi to be transversely 
 divided in their middle, and the posterior half drawn 
 towards the middle lobe, by which means the point at 
 the under surface of the corpus striatum is brought 
 into view, from whence the commissure issues, and its 
 exposure in either direction may be completed. 
 
 I have recently employed upon separate portions of 
 brain the following mode of preparation, which faci- 
 litates greatly the separation of its fibres. Portions 
 of brain are to be placed in oil of turpentine, ma- 
 
Ill 
 
 cerated for from four to six days, and subsequently 
 hardened in alkohol. The turpentine is frequently to 
 be changed on the portions of brain, which should be 
 kept in a cool place. 
 
 Explanation of the Twelfth Plate. 
 
 The fissura Sylvii having been treated as for Plate 
 X., the outer wall of the capsule is peeled from the 
 outer portion of the corpus striatum. The upper 
 margin of the latter is semicircular, or nearly so ; the 
 under margin nearly straight, but lower before than 
 behind; its outer and under surface are somewhat 
 convex ; its thickness is greatest below, whence it con- 
 tinually narrows towards its upper, sharp, and curvi- 
 linear margin. The outer wall of the capsule de- 
 cussates at this margin the inner wall formed by 
 the fibrous cone. The hamular fasciculi are cut 
 through in their middle, and the posterior half drawn 
 off towards the middle lobe. At the upper part, fas- 
 ciculi are seen belonging again to the intermediate and 
 connecting stratum. Their disposition is extremely in- 
 tricate; they form a mass less white, and exhibiting 
 more vascular pores than the medulla of the convolu- 
 tions which rest upon them. 
 
 a. h. c. The margin of the hemisphere. 
 d. The anterior part of the hamular fasciculi, which 
 pass to the anterior lobe. 
 
112 
 
 e. The body of the anterior commissure emerging 
 from the outer portion of the corpus striatum, inclining 
 backwards, ending in divergent fasciculi, which blend 
 with the radiation of the outer and inner walls of the 
 capsule. 
 
 Jl The intermediate layer of medullary fasciculi 
 which seem interposed between the convolutions and 
 nucleus of the cerebrum. 
 
 g. A portion of the outer wall of the capsule left 
 attached, and so lifted as to show the decussation of 
 its fibres with those of the inner wall. 
 
IIS 
 
 Of the Septum Liidduvi, the Fornix, and the Ventricles 
 of the Brain, by Professor Beil. Archiven fiir die 
 Physiologie . Eilfter band, p. 101 — 116. 
 
 XVIII 
 
 Of the Septum Lucidum and its Ventricle. 
 
 The septum lucidum is interposed like a medias- 
 tinum between the lateral ventricles, and in a similar 
 manner is formed by the reflection of two layers of the 
 lining membrane (in this case the epithelium), one de- 
 rived from either cavity, which it assists in separating. 
 The septum has an ill-defined, triangular margin, 
 bounded by curved lines; its inferior angle reaches to 
 the anterior commissure, where it lies exposed between 
 the anterior crura of the fornix and the fillets of the 
 lamina cribrosa ; its apex is found between the fornix 
 and the corpus callosum, in the vicinity of the lyra ; 
 its third and rounded angle at the concave surface of 
 the anterior fold of the corpus callosum. The base 
 of this triangle is short ; the under concave and the 
 upper convex margin of the septum form the longest 
 sides. At the fore part the septum begins by the 
 meeting of either layer of epithelium upon the anterior 
 
 1 
 
114 
 
 commissure ; and the base of the triangle, above sup- 
 posed, is formed by an extension of the septum from 
 this point to the bend of the corpus callosum, and cor- 
 responds with a linear furrow, which is seen on the 
 base of the brain between the fillets of the lamina cri- 
 brosa. From the posterior extremity of this furrow, 
 which immediately touches the anterior commissure, a 
 delicate membrane extends to the commissura tractuum 
 opticorum, and thus is the base of the brain completed 
 anteriorly. Again, from this linear furrow, the du- 
 plicature of the septum may be unfolded, and the 
 division of the brain into two similar lateral portions 
 effected. 
 
 Between the layers of the septut . a shut ventricle, 
 clothed with a proper epithelium, exists. This ventricle 
 is from a line to a line and a half in breadth at its 
 fore part, where it extends between either surface of 
 the reflected fold of the corpus callosum : thence it be- 
 comes narrower backward, and ends in a point above 
 the lyra. The septum contains, within its double layer 
 of epithelium, fibres derived from the fillets of the 
 lamina cribrosa, and from the upper surface of the 
 fornix. 
 
115 
 
 XIX. 
 
 Of the Fornix. 
 
 The root of either anterior crus begins in either 
 thalamus, between its superficial plates, about a line 
 below its upper surface, under a distinct eminence at 
 its fore part near the taenia : the root descends, being 
 first inclined backwards, then forwards abut opposite to 
 the lower margiii of the commissura mollis, splits into 
 two or three fasciculi, and emerging upon the under 
 surface of the braiii, forms, by its reflection, the corpus 
 albicans. This substance contains gray matter ; the 
 chord prolonged from it, and termed the anterior crus, 
 ascends before the thalamus, and derives, from the 
 medullary border of its inner and upper margin, a 
 slender fasciculus at a point over against the anterior 
 commissure ; otherwise the concave edge of the crus 
 is unattached. The convex side is in adhesion with 
 the septum lucidum, and gives to that body slender 
 fasciculi joining those of the fillet. 
 
 Above the anterior commissure either crus of the 
 fornix, before cylindrical and apart, becomes flattened 
 and in apposition with its fellow; and thus the body 
 of the fornix begins, which is extended directly back- 
 ward, and terminates, where the lateral portions, yet 
 further flattened, diverge, and become posterior crura. 
 The inner margins of the lateral portions of the fornix 
 
 I 2 
 
H6 
 
 behind adhere to the corpus callosum, and thus close 
 the pointed extremity of the ventricle of the septum 
 lucidum : the outer unattached margins slope down- 
 wards. The lyra is the surface which begins at the 
 divergence of the posterior crura: in most instances it 
 seems to be but the extremity of the posterior fold of 
 the corpus callosum, and not to derive fibres from the 
 inner margins of the posterior crura of the fornix. A 
 process of the posterior crus extends backward between 
 the layers derived from the upper and under parts of 
 the posterior fold, to lose itself in the convolutions of 
 the posterior lobe of the brain. 
 
 The posterior crus of the fornix, in connection with 
 fasciculi from the posterior fold of the corpus callosum, 
 finally extends towards the middle lobe, to form, with 
 the long internal convolution, the hippocampus major. 
 The fasciculi from the fornix form in part the covering 
 of the hippocampus ; in part, its loose fold, the taenia 
 hippocampi. These fasciculi are very delicate, and 
 have a direction from within outward. The gray sub- 
 stance of the hippocampus appears first as a narrow 
 layer upon the posterior fold of the corpus callosum. 
 Where it lies as indented border between the tsenia 
 hippocampi and the long convolution, with the latter 
 of which it has no direct continuation, its surface is 
 transversely furrowed, and partly cribriform ; it ter- 
 minates by several processes in the pes hippocampi. 
 
 In some animals the fornix is developed inversely as 
 the other parts of the brain. The fornix extends from 
 the gray matter of the thalami to that contained in the 
 
117 
 
 hippocampus. It is composed of delicate, and intri- 
 cately woven, flax-like fibrils. In each lateral portion a 
 central vessel is found, and, at its margin, the gill-like 
 flexus choroides. The fornix unites remote parts in 
 the length, the anterior commissure in the breadth of 
 the brain. Like these, the corpus callosum involves 
 no gray matter, and, with them, perhaps, forms an 
 apparatus for transmission merely. 
 
 The brain seems composed of one set of fasciculi 
 which diverge, of another, which converge. Its ge- 
 neral form, and that of its parts, is spherical: its inte- 
 rior structure is almost every where fibrous. 
 
 XX. 
 
 The venti’icles result from the horizontal apposition 
 of the corpus callosum to the ascending and diverging 
 crura cerebri: properly there is but one extensive 
 cavity, which surrounds the thalami, extending (as the 
 third ventricle) below them to the infundibulum, and 
 through the aqueduct to what is termed the fourth ; 
 and this is not every where enclosed by cerebral sur- 
 faces; but is open below the lyra, and at the lower 
 aperture of the fourth ventricle. 
 
 To illustrate the preceding details, a brain should be 
 thus prepared. The two hemispheres should be hori- 
 zontally removed above the corpus callosum, and the 
 anterior half of the long convolution peeled off. The 
 fore part of the corpus callosum should the be cut 
 
118 
 
 through in the median plane, so as to allow of the 
 exact separation of the layers of the septum lucidum ; 
 and the section afterwards carried completely through 
 it. The posterior half of the long convolution is 
 now to be removed, bringing away with it laterally as 
 many adjoining convolutions as may suffice to show 
 the course of the fasciculi, which are derived from the 
 posterior fold of the corpus callosum to the posterior 
 and inferior horns of the lateral venticle : the gray sub- 
 stance may then be removed from the interior of the 
 hippocampus. 
 
119 
 
 Supplement to the Anatomy of the Cerebrum and Cere- 
 bellum, by Professor Reil. Archiven fur die Phy- 
 siologie. EUfter band, p. 345 — 376. 
 
 XXL 
 
 Of the Cerebrum, 
 
 The pyramids, which are the elementary parts of 
 the crura cerebri, become broader in their separate 
 ascent through the annular protuberance, and above 
 this body still enlarging recede from each other. The 
 corpus callosum placed horizontally on their summits 
 encloses with them the general cavity of the cerebral 
 ventricles. 
 
 The form of the corpus callosum is well illustrated, 
 by supposing all its parts attracted towards its centre. 
 To exhibit its outer surface completely, a single entire 
 hemisphere, and a brain with the hemispheres cut 
 horizontally off half an inch above its level, are re- 
 quired : from the latter preparation again the long 
 convolution, which contains the covered bands, with 
 these is to be rent off, so as to expose the transverse 
 course of the middle fasciculi, and the radiation of the 
 extreme fasciculi of the corpus callosum. 
 
 It may now be seen that the anterior fold of the 
 corpus callosum ends with a distinct concave margin 
 
120 
 
 a full quarter of an inch before the anterior commis- 
 sure. From this margin a furrow extends backwards, 
 either half of which results from a reflection of the 
 epithelium, which invests the anterior horn of the la- 
 teral ventricle, and assists in forming the septum luci- 
 dum : a rent from this furrow, therefox’e, would split 
 the base of the septum. Along either margin of this 
 furrow a white band, continuous with the medulla in- 
 cognita, is seen to extend to the edge of the anterior 
 fold of the corpus callosum, at which point a blind 
 foramen exists : the two white bands are the fillets of 
 the lamina cribrosa. Medullary fasciculi are generally 
 observed to be derived from them, which in most cases 
 plunge in by the blind foramen, and lose themselves 
 in the septum lucidum; but sometimes are continued 
 along the convex surface of the anterior fold of the 
 corpus callosum to join the linea Lancisii. A thin 
 layer of nervous matter is continued from the furrow 
 and posterior margins of the fillets, to the commissura 
 tractuum opticorum, closing the third ventricle at the 
 fore part. The concave extremity of the anterior fold, 
 the fillets, the lamina cribrosa, and the gray matter of 
 the inner and inferior convolutions of the anterior 
 lobes, are reciprocally continuous. The lateral ex- 
 pansion of the extremity of the anterior fold of the 
 corpus callosum, which extends to join the hamular 
 fasciculi, and to constitute the outer wall of the cap- 
 sule, is shown by breaking through the furrow between 
 the fillets for the depth of a quarter of an inch, and 
 then carrying the rent horizontally outwards. 
 
121 
 
 When the long convolutions are broken oflF from an 
 entire brain, the breadth of the corpus callosum ap- 
 pears doubled ; the structure ascribed to this body con- 
 tinues unaltered till beyond the outer margin of the 
 covered bands, where the substance of the outer layer 
 of the corpus callosum appears reflected into the me- 
 dulla of the convolutions, and with the latter peels into 
 plates and fibrils. In quadrupeds, both margins of the 
 corpus callosum are similarly folded : the posterior 
 does not, as in human beings, form a broad layer 
 closely applied to the opposite surface. 
 
 The covered bands are lodged in distinct furrows 
 apon the corpus callosum ; they terminate anteriorly 
 at the meeting of the fillets of the lamina cribrosa with 
 
 o 
 
 the anterior fold of the corpus callosum, becoming 
 more delicate as they approach this point, and finally 
 fibrous and reciprocally continuous. On the other 
 hand, turning round the posterior fold within the long 
 convolution, they give off’ one delicate radiation, which 
 joins and is interwoven with that derived from the 
 posterior fold to the floor of the posterior and inferior 
 horns ; their larger portion on either side becoming 
 continuous with the medulla of the extremity of the 
 long convolution now employed in the formation of 
 the hippocampus. 
 
 After the preparation of the fissura Sylvii, as already 
 described, if a rent be carried horizontally from the 
 upper surface of the corpus callosum, and in the same 
 manner the course of its deeper fasciculi be traced to the 
 upper margin of the capsule, they are found to become 
 
122 
 
 continuous with the fasciculi of its inner and outer 
 wall. In this way the nucleus of the brain may be 
 stripped of its convolutions. 
 
 Between the corpus callosum and convex margin of 
 the inner portion of the corpus striatum, is found the 
 layer of medulla befox’e alluded to, which may be 
 termed the semilunar border [halb-mond-fbrmiger 
 saum] : its greatest breadth is at its middle, whence it 
 tapers to either pointed extremity. By this mass the 
 fasciculi of the fibrous cone are bound together, upon 
 emerging from the gray portions of the striated body : 
 above it the fasciculi of the fibrous cone and corpus 
 callosum meet, and if a rent be carried directly for- 
 ward from it to the fore part of the anterior lobe, fas- 
 ciculi, derived from the anterior fold of the latter, are 
 seen to run forward and parallel and internal to the 
 foremost fasciculi of the cone, in this respect coinciding 
 with the radiation of the posterior fold. The medullary 
 layer at the outer margin of the corpus striatum breaks 
 into curvilinear processes, one lying behind the other. 
 It seems to have no regular structure. In human 
 brains it becomes thinner backwards, and ends towards 
 the posterior margin of either thalamus in a somewhat 
 reticular disposition : in the brains of quadrupeds this 
 substance is more developed posteriorly, and is the 
 source of the tapetum. In the brain of an adult per- 
 son, the ventricles of which were extraordinarily dis- 
 tended with water, the fasciculi of the corpus callosum 
 and of the fibrous cone were found continuous at the 
 chamber containing the substance now described: 
 
123 
 
 the convolutions were in this instance no ways 
 changed. 
 
 It may be remarked that the medullary substance in 
 general is that, to which a definite structure is to be re- 
 ferred, and that the gray matter is rather enclosed in 
 the interstices of the former, or thrown into globular 
 portions, or as a layer upon its surface. The substance, 
 which mechanically connects the remote convolutions 
 in the brain, and is interposed between these and the 
 nucleus, is permeated by more vessels, is softer, and of a 
 browner tint, than the medulla generally. The taenia 
 semicircularis geminum is formed of fibres, which 
 proceed obliquely backwards and outwards from the 
 upper surface of the thalamus, and are strengthened 
 by a fold of epithelium. The taenia is thickened as it 
 passes along the posterior margin of the thalamus, 
 and terminates finally, after having somewhat reticu- 
 larly invested the inner half of the roof of the inferior 
 horn, in the obtuse extremity of the middle lobe, which 
 adheres to the lamina cribrosa : between the tsenia and 
 the tapetum in the inferior horn, the tail-like process 
 of the inner portion of the corpus striatum is pro- 
 longed to its extremity, and may with care be raised : 
 here and there its gray substance seems changed for 
 medullary matter, which separates in fibrils or reticular 
 layers. 
 
 The gray kernels of the globular portions of the 
 cerebral nucleus require further consideration. Those 
 in the posterior tubercles are well shown in Plate XI, 
 as they are exposed on the removal of the epithelium 
 
124 
 
 and a thin medullary layer; they are about the size of 
 a barley-corn, and lie with their points towards each 
 other. 
 
 The bed of gray substance analogous to them in 
 either thalamus occupies its internal and posterior 
 part : from this are derived fasciculi, which partly join 
 the radiation of the fibrous cone, occupying its fore 
 part ; but some fasciculi internal to the others, bend 
 round the margin of the crus cerebri, forming the me- 
 dulla incognita. This substance finally is of peculiar 
 character, neither gray nor white ; it adheres to the 
 outer margin of the tractus opticus. 
 
 Explanation of Plate XIII. 
 
 The present engraving is an improvement upon 
 Plate IX, to the remarks accompanying which the 
 reader is referred for the method of dissection. 
 
 A. A. The anterior, 
 
 B. B. The middle, 
 
 C. C. The posterior lobes of the brain seen from 
 below, after a section in the median plane, extending 
 to the corpus callosum, and allowing a partial separa- 
 tion of the hemispheres. 
 
 D. D. Section of the crui’a cerebri. 
 
 E. E. Surfaces resulting from a longitudinal sec- 
 tion of the floor of the posterior horn of the lateral 
 ventricle. 
 
125 
 
 F. F. Meant to represent portions of the walls of 
 the inferior horns turned aside. 
 
 G. G. The pes hippocampi on either side. 
 
 H. H. The indented border. 
 
 a. The extremity of the anterior fold of the corpus 
 callosum, separated laterally from the inner surface of 
 the anterior lobe. 
 
 b. b. The lines, along which the covered bands 
 are placed : within these the corpus callosum is com- 
 posed of flat fasciculi. Externally it rends in foliated 
 plates, which appear continuous with the ordinary 
 structure of the convolutions. 
 
 c. c. c. c. Torn surfaces of the inner convolutions of 
 the anterior lobes. 
 
 d. The concave margin of the anterior fold of the 
 corpus callosum. 
 
 e. The membranous continuation of the anterior 
 fold formed by the epithelium of the anterior horns 
 of the lateral ventricles ; on it are seen the fillets of 
 the lamina cribrosa. 
 
 f. f. Section of the commissura tractuum opticorum. 
 
 g. g. Section of the anterior commissure. 
 
 h. h. Section of the commissura mollis, pineal gland, 
 and tubercula. 
 
 i. Root of the anterior crus of the fornix, supposed 
 to be seen in its course within the thalamus. 
 
 k. Its nodule, or corpus albicans. 
 
 I. Anterior crus of the fornix. 
 
 VI. Fasciculus joining it, derived from the inner 
 and upper margin of the thalamus. 
 
126 
 
 n. Meant to represent the third nerve. 
 
 0. Under surface of the corpus callosum, deprived 
 of epithelium. 
 
 p. Radiated expansion of the corpus callosum be- 
 hind the thalamus, below that of the fibrous cone, 
 forming the tapetum, and extending to the extremity 
 of the postei’ior horn. 
 
 q. Radiation of the taenia semicircularis in the infe- 
 rior horn, forming a tapetum for the inner half of its 
 roof. 
 
 r. Radiation of the corpus callosum, forming a 
 tapetum for the outer part of the roof of the inferior 
 horn: between the two, the cauda of the corpus cal- 
 losum extends. 
 
 s. Termination of the tapetum, where the roof and 
 floor of the inferior horn meet. A decussation of its 
 fibres seems to take place with those of the fibrous 
 cone, and of the intermediate connecting stratum. 
 
 t. Points, at which fasciculi of the corpus callosum 
 and of the fibrous cone meet, in part uniting with, in 
 part decussating each other. 
 
 u. Fasciculi of the corpus callosum, extending into 
 the posterior lobe, with the convolutions in which they 
 appear continuous, as they are parallel to the adjacent 
 fasciculi of the fibrous cone. 
 
 V. Central layers of the corpus callosum, in part 
 disposed below, in part becoming continuous with the 
 substance of the fibrous cone. 
 
 w. The posterior fold of the corpus callosum, which 
 
127 
 
 is thickest at its middle, and laterally indented by the 
 long convolution. 
 
 X. Posterior extremity of the fornix. The inner part 
 is seen to extend backwards above the folded part of 
 the corpus callosum : the outer, which alone properly 
 constitutes the crus, is cut short. 
 
 y. z. Radiation of the posterior fold of the corpus 
 callosum in the posterior, and towards the inferior 
 horn of the lateral ventricle. 
 
 1. 2. Radiation of the fibrous cone. 
 
 3. The semilunar border. 
 
 4. 4. Line along the posterior margin of the thala- 
 mus, at which the fasciculi of the fibrous cone ai*e not 
 covered with a tapetum. 
 
 5. Radiation from the posterior extremity of the 
 thalamus, which blends in the inferior horn with that 
 of the fibrous cone. 
 
 Plate XIV. 
 
 represents the connection between the fasciculi of 
 the corpus callosum and those of the fibrous cone. 
 
 a. a. a. Corpus callosum, with the tapetum derived 
 from it. 
 
 b. h. h. Radiation of the fibrous cone from the outer 
 margin of the thalamus : the foremost fasciculi appear 
 to meet those of the corpus callosum at right angles, 
 the middle fasciculi to become directly continuous 
 
128 
 
 with the latter, and the posterior, to be extended in a 
 separate layer above them. 
 
 XXII. 
 
 Of the Cerebellum, 
 
 The ciliary body has the appearance of a flattened 
 cone, the truncated apex of which is directed forward, 
 the base backward : it is composed of a plate of gray 
 matter, irregularly crumpled in doubled folds, giving 
 it outwardly the appearance of portions of intestine 
 in parallel apposition. Before its obtuse point, and at 
 the margin where the anterior peduncle disappears, 
 is a cribriform surface for the transmission of its ves- 
 sels. The anterior peduncles of the cerebellum pass 
 into the ciliary body, between the folds of which and 
 between the fasciculi of the anterior peduncles, tubes 
 are found in the nervous matter, reddened with blood, 
 and directed from before backward, showing the 
 course of blood-vessels. The ciliary body is covered 
 above by the lateral and inferior peduncles of the ce- 
 rebellum : before and externally, where the outer mar- 
 gin of the inferior velum is attached, its projecting 
 edge is covered by epithelium alone ; behind, its 
 shorter process is covered by the stems of the thin 
 lobe, of the biventral lobe, and by the band extending 
 from the root of the almond to the spigot. The ciliary 
 
129 
 
 bodies lie strictly in the hemispheres of the cerebellum, 
 whence it happens that they are wanting in animals 
 which have diminutive hemispheres, or none at all. 
 
 The ciliary body may be conveniently described as 
 consisting of an upper and an under layer. The 
 upper layer begins as far forward as the cribriform 
 plate above-mentioned, where it has the breadth of the 
 anterior peduncle. As the latter becomes broader, so 
 doestheupper layer of theciliary body, which terminates 
 where the upper and posterior lobe meets the nucleus 
 of the hemisphere. It appears probable, but it is very 
 difficult to determine, that the two layers are conti- 
 nuous at their posterior margin, and thus enclose a 
 cavity filled with fasciculi from the anterior peduncle : 
 laterally the two layers are distinctly continuous. The 
 under layer has a long and a short process, which 
 mark the boundaries of the nidus. The long process 
 is external, reaches downward to the inferior pe- 
 duncle, and ends in the eminence already spoken of. 
 The short process ascends transversely across the 
 anterior peduncle to its inner margin, and opposite to 
 the stem of the pyramid unites with the upper layer. 
 The ciliary body has some analogy with the hippo- 
 campus; the cineritious matter in which is folded, 
 though not indented, except at its margin, and is too 
 of a grayer colour. The corpus ciliare may be a 
 ganglion ; that is to say, may belong to the same class 
 of parts with the corpora striata and the thalami. Like 
 these, it has a lamina cribrosa, is very vascular, and is 
 
 K 
 
130 
 
 of a yellower grey; its structure yet requires much 
 elucidation. 
 
 In preparing a cerebellum for showing this part, 
 after moderate hardening in alkohol, the square lobe, 
 and the thin and biventral lobes should be removed, 
 and the remainder placed for two days in oil of turpen- 
 tine. The under layer of the ciliary body is to be first 
 exposed by the removal of the flock, the exposure of 
 the inferior peduncle, the detaching of the velum and 
 the epithelium. The projecting extremity of the long 
 process of the under layer of the ciliary body is now 
 visible at the outer margin of the superior peduncle, 
 and immediately behind the inferior peduncle. By 
 pressing off the medullary plates belonging to the thin 
 and the biventral lobes, what remains of the under 
 surface of the ciliary body is readily denuded. The 
 exposure of the upper layer must be begun at its inner 
 and anterior margin, where the superior vermiform 
 process joins the hemisphere, and the superjacent 
 medulla raised outwards towards the horizontal fissure. 
 
 The union between the vermiform processes and 
 the hemispheres of the cerebellum is something dif- 
 ferent from simple continuity. When the square lobe 
 is raised from the horizontal fissure, it does not carry 
 with it the superior vermiform process, but breaks off 
 abruptly at its margin, where a sort of interweaving 
 or suture exists. There are three points in the superior 
 vermiform process, viz. between d and e, e and g-, 
 g and h (Tab. III.), where the laminae admit of being 
 
131 
 
 pressed down the axis of one stem, and continuously 
 torn from that of the opposite stem, leaving globular 
 cavities ; for, laterally, at the suture, the same abrupt 
 breaking off occurs, as that just mentioned. On the 
 other hand, the pyramid, the spigot, and the nodule, 
 have but little lateral attachment to either hemisphere, 
 and may be rent olF in a direction parallel to the an- 
 terior medullary velum, which appears to pass into the 
 nucleus of the general commissure as a partition be- 
 tween the vermiform processes. 
 
 The black substance of the fourth ventricle 
 ascends along the under surface of the anterior pe- 
 duncles of the cerebellum. On the removal of this 
 substance with the epithelium, it is seen that there is 
 no communication between the anterior and lateral 
 peduncles. On the other hand, the outer fasciculus 
 of the anterior peduncle appears to join the posterior 
 peduncle immediately beyond the last nodule of the 
 ciliary body. The roof of the chamber for the origin 
 of the fifth nerve seems exclusively formed by the an- 
 terior peduncle. 
 
 O'f 
 
 'id Of 
 
 } JLji C 
 
 ’^8ant> t 
 
132 
 
 licmarks upon the Spinal Chord -and the Nervous 
 System generally. 
 
 In this and the preceding number I have now pub- 
 lislied the substance of all the essays of Reil on the 
 structure of the brain, which are contained in his 
 Archiven fiir die Physiologie. I should have closely 
 translated the original, but that the introductoiy re- 
 marks are uninteresting, and the descriptive parts, at 
 the same time that they are exceedingly elaborate and 
 minute, as well as strictly accurate, are yet wanting in 
 precision and method, and involve frequent repeti- 
 tions. As it is, I have abridged many parts. Those 
 who may take the trouble of studying these essays will 
 do well first to consult the adjoined engi-avings and 
 accompanying references, and to endeavour to dissect 
 hardened brains in imitation of such preparations, as 
 the drawings represent ; subsequently to which it will 
 be found easy to verify the statements contained in the 
 preliminary passages. 
 
 Notwithstanding the profound and successful re- 
 searches of Professor Reil, much yet remains to be 
 ascertained in order to complete a theory of the 
 structure of the brain ; and it is probable that the 
 principal source, from which a further illustration of 
 this important subject may be expected^ consists in an 
 extensive application of the method of Reil to com- 
 
133 
 
 parative anatomy. I have not as yet given up any 
 time to the inquiries to which I allude ; but I have 
 pursued them sufficiently to convince me of their 
 value- I take the present occasion of mentioning a 
 few circumstances relating to the spinal chord. 
 
 The spinal chord has a furrow before and behind 
 in the median plane, and one again on either side of 
 and parallel to each of these, at which the filamentous 
 roots of the spinal nerves are attached. 
 
 When the spinal chord has been macerated in al- 
 kohol for two months and upwards, and its investing 
 membranes have been removed, if the walls of the an- 
 terior median furrow be pressed aside, a cribriform 
 surface is exposed, which has the appearance of being 
 composed of transverse fibres. 
 
 If a transverse section be made of the spinal chord, 
 an oval or semilunar portion of gray matter is seen to 
 occupy the interior of either half, and, in the centre, 
 apparently to unite with its fellow : one horn of either 
 points forwards and outwards, the other backwards 
 and outwards towards the posterior lateral furrow. 
 
 If the anterior median furrow be pressed open, a 
 rent may be carried from the cribriform surface to 
 either posterior lateral furrow, and the smaller portion 
 of the three thus separated admits readily of division 
 in the median plane. The medullary substance of the 
 spinal chord tears in longitudinal and parallel fasciculi, 
 which seem to be united reticularly, so that the un- 
 folded surface has much the appearance of the in- 
 terior of a turtle’s small intestine. I'he gray substance 
 
184 . 
 
 appears in part to be disposed in a similar way. The 
 posterior roots of the spinal nerves appear to me to 
 extend towards the gray substance ; but I have not as 
 yet been able to trace either these or the anterior fas- 
 ciculi distinctly to that oi’igin. In a spinal chord, 
 which had been macerated in alkohol for two years, 
 I found a transverse and cribriform plate extending 
 across the middle of the spinal chord, which tore into 
 parallel and transverse fibres. 
 
 The connection of the parts of the spinal chord 
 with those of the medulla oblongata has appeared to 
 me the following. If the posterior pyramid be detached 
 from themarginof the lozenge-shaped field of the fourth 
 venti’icle, it appears prolonged as a fasciculus on either 
 side of the posterior median furrow. If the corpus 
 restiforme be detached from the cerebellum, and drawn 
 downwards, it carries with it a broad lateral surface 
 of the spinal chord, including in its centre the posterior 
 lateral furrow. If all the superficial substance between 
 the internal margin of the corpus restiforme and the 
 anterior pyramid, that is to say, the coipus olivare, 
 with its laterally adherent fasciculi, be drawn downward, 
 the remaining surface of the spinal chord is raised, 
 which contains the anterior lateral furrow. Finally, 
 if the anterior pyramid be divided at the inferior 
 margin of the annular protuberance, and drawn down- 
 wards, it is seen, at an inch from the latter substance, 
 to dip obliquely backwards, to cross over to the op- 
 posite side, decussating the fasciculi of its fellow, and 
 then apparently to descend in the length of the spinal 
 
135 
 
 chord within the prolongation of the corpus restiforme, 
 accompanied, it would seem, by an extension of sub- 
 stance from the floor of the fourth ventricle. After 
 tearing asunder the two lateral portions of the medulla 
 oblongata, from either rent surface a thin stratum may 
 be raised, which is composed of parallel fibres, extend- 
 ing directly from the anterior to the posterior median 
 furrow : between these fibres vessels are lodged. 
 
 To pass from the preceding details to a general 
 consideration of the nervous system, it may be re- 
 marked : 
 
 1. That, in vertebral animals, in mollusca, in arti- 
 culated animals, and in the higher zoophytes, as, to 
 specify an individual, in the Asterias aurantiaca, the 
 nervous system consists of two distinct parts ; of a 
 centre, which has a^ certain relation to the form of the 
 animal, and of medullary chords, or nerves, derived 
 from that centre to different organs. 
 
 2. That in the families of animals above enumerated, 
 the nerves of sensation and motion, which supply any 
 given region in the body, are derived from one and the 
 same part in the nervous centre. 
 
 3. That, in connection with this anatomical law, an 
 influence may be propagated from the sentient nerves 
 of a part, to their correspondent nerves of motion, 
 through the intervention of that part alone of the 
 nervous centre, to which they are mutually attached. 
 Thus in vertebral animals, in which alone the fact is 
 questionable, when the spinal chord has been divided m 
 two places, an injury of the skin of either region is 
 
136 
 
 followed by n distinct muscular action of that part. 
 Again, if the brain be quickly removed from the head 
 of a decapitated pigeon, excepting only the fore part 
 of the crura cerebri, together with the tubercles and 
 the second and third nerves, on pinching the second 
 nerve the iris contracts, 
 
 4. That each individual among the animals above 
 specified, at one time or another, executes instinctive 
 movements. Thus animals newly born instinctively 
 select and convey to their alimentary cavity their 
 proper food. Instinct is an arbitrary connection be- 
 tween certain internal feelings, and the will to execute 
 particular movements which, in this case, do not pro- 
 ceed from imitation, habit, or the expectation of an 
 advantage to be derived from them. The same actions, 
 which are at one time instinctive, may, at another, 
 spring from a different principle. 
 
 5. That the nervous centre, which, in the Asterias 
 aurantiaca, according to Tiedeman, consists of an 
 equal ring, with five points (corresponding with the 
 five rays of the animal), at which nerves are given off, 
 gradually, in the scale of improvement, becomes dis- 
 proportionately developed at one part, which is, or 
 corresponds with, the brain. In the Laplysia fasciata, 
 M. Cuvier describes the nervous centre as consisting’ 
 of five ganglions, united by medullary chords; of 
 which one is placed upon the oesophagus, and is united 
 to a second and a third, one on either side, by three 
 medullary chords; and to a fourth, placed below the 
 mouth, by two filaments. The fifth ganglion, which 
 
is remote from the four preceding, is united by one 
 filament to each lateral ganghon *. 
 
 * M. Cuvier describes the superior oesophageal ganglion . 
 as the brain of the Laplysia. It would appear, from the 
 following description, by M, Cuvier, of the distribution of 
 the nerves in this animal, that the suboral ganglion has an 
 equal right to be considered equivalent to a medulla ob- 
 longata. I have besides in view, in this note, the illus- 
 tration of my second general position. 
 
 “ Le ganglion inferieur ou suboral donne quatre nerfs 
 de chaque cote, un pour I'cesophage et les glandes sali- 
 vaires, et trois pour les muscles de la bouche. 
 
 “ Le cerveau en fournit trois de chaque cote pour les 
 parties musculaires de la tete, dont ceux du cote droit 
 donnent des filets a la verge, et un pour le grand ten- 
 tacule, qui donae une branche a I’ceil. 
 
 “ Chacun des ganglions lateraux en donne douze ou 
 treize, qui se perdent tous dans les parties musculaires de 
 la grande enveloppe du corps : je les ai representes avec 
 exactitude. Le petit collier, qui passe sous I’artere, en 
 donne un impair. 
 
 “ Les visceres reqoivent les leurs d'un ganglion a part, 
 qui fait par consequent I’office de sympathique ; c’est le 
 quatrieme, ou le petit. II donne un nerf au foie et aux 
 intestins, un autre aux parties de la generation ; celui-ci 
 forme encore un ganglion presque imperceptible, mais 
 rouge comme les autres ; un troisieme aux branchies ; le 
 quatrieme se perd dans les parties musculaires situees 
 sous Ic couvercle.” — Cuvier, Mem. des Mollusques. 
 
138 
 
 6. That, in connection with this change in the form 
 of the nervous centre, the nervous influence, which, 
 in the Asterias, appears equally diffused, and in each 
 region independent and sufficient for itself, is now 
 accumulated towards the brain, or parts corresponding 
 with it, the separation of which impairs the functions 
 of the rest. 
 
 M. Cuvier mentions, that a separated ray of the 
 star-fish will live by itself M. Rolando mentions, 
 that, on removing two of the ganglions from the oeso- 
 phagus of the Laplysia, the animal quickly perishes. 
 
 7. That, in vertebral animals, the form and bulk of 
 the cerebellum, and of the hemispheres of the cere- 
 brum, appear to have no fixed relation to that of the 
 spinal chord, medulla oblongata, and the adjoined 
 tubercles. 
 
 8. That from the history of acephalous infants, 
 which have survived their birth for a short period, it 
 appears that movements, resembling instinctive move- 
 ments, have been performed by human beings, in 
 which the cerebellum, and the hemispheres of the 
 cerebrum, were wanting. 
 
 It is exti’emely difficult to determine by experiments 
 the precise value of parts of the nervous centre, in as 
 much as the results, which ensue on its partial removal, 
 may depend as well indirectly as directly upon the in- 
 jury. It is well known, that some very successful at- 
 tempts have been recently made by MM. Rolando, 
 Flcurens, Majendie, Serres, the details of which are 
 contained in M. Majendie’s Journal, to illustrate the 
 
189 
 
 influence of the cerebrum and the cerebellum. If the 
 experiments to which I allude lead as yet to no definite 
 conclusion, for the reason assigned above, the facts 
 which they disclose are yet full of interest. 
 
 After the removal of the upper part of the cere- 
 bellum, pigeons stagger as if intoxicated. After the 
 entire removal of the cerebellum, they throw them- 
 selves convulsively backwards, and revolve in a ver- 
 tical plane ; then lie forward on their breasts, their 
 heads bent backwards, their wings half extended, and 
 unable to sustain themselves on their legs : they are 
 sensible, and, when excited, move all their parts con- 
 vulsively. These effects I have witnessed on repeating 
 expei’iments of M. Fleurens. 
 
 M. Serres ascertained, that the destruction of one 
 hemisphere of the cerebellum in dogs and hoi’ses pro- 
 duces an hemiplegia of the opposite side. 
 
 After the removal of the tubercles, pigeons and frogs 
 move round and round in the horizontal plane. Frogs 
 stop, and then spontaneously resume this movement. 
 After the removal of the hemispheres of the cerebrum 
 above the tubercles, pigeons seem stupified, but sustain 
 themselves on their feet, and, when roused, exhibit 
 their usual gestures for a brief space. Frogs move 
 about ^s briskly, and with the same precision, as before 
 the removal of the hemispheres. M. Rolando further 
 mentions, that certain cold-blooded animals seem in- 
 capable of loco-motion after the removal of the cere- 
 bellum. 
 
 These facts seem indeed to show, as M. Rolando and 
 
140 
 
 M. Fleurens have supposed, that the cerebellum has 
 greatly to do with loco-motion ; but it is by no means 
 determined by them that this oi'gan is the source of 
 loco-motion, as the former or the regulator of loco- 
 motion, as the latter physiologist infers. If the cranial 
 cavity of a living pigeon be exposed, and all the parts 
 anterior to the cerebellum be separated from the cere- 
 bellum and the medulla oblongata by a vertical in- 
 cision, not made with any violence, the bird falls con- 
 vulsed, and much in the same state as after the removal 
 of the cerebellum. Again, if the cerebellum of a frog 
 be removed, the animal moves about at first as briskly 
 as before the injury. If then the tubercles and cerebral 
 hemispheres be removed, leaving the medulla oblon- 
 gata and crui’a cerebri entire, the movements of the 
 animal continue, but it has a tendency to move round 
 and round, and rather crawls than springs. Finally, 
 if the medulla oblongata and crura cerebri be separated 
 from the spinal chord, the animal lies relaxed and all 
 but lifeless, though still for a while an injury of one of 
 its extremities will produce motion in one or more 
 limbs, and sometimes of its entire body. 
 
 The additional experiments immediately wanted to 
 illustrate this subject consist in the division of the 
 three peduncles of the cerebellum, of either pair singly, 
 as well as in different combinations. The corpora 
 restiformia, which are in some degree of connection 
 with the cutaneous portions of the spinal nerves, expand 
 in the cerebellum towards its circumference. The 
 lateral peduncles derived from the substance of the 
 
141 
 
 cerebellum are interwoven with the fasciculi of the 
 pyramids. The superior peduncles again, on emerging 
 from the cerebellum, ascend towards the tubercula 
 quadrigemina and thalami, with which they are in 
 some degree connected, as well as with the black 
 matter, and with the origins of the fourth nerves: 
 subsequently, either superior peduncle is inclined 
 downward through the cylinder of the crus cerebri 
 towards its crust, being finally brought into connection 
 with the surface from whence the third nerve arises, 
 and with the fasciculi derived from the pyramids and 
 corpora olivaria, which, in their inferior continuation, 
 are more or less associated with the remaining volun- 
 tary nerves. 
 
 THE END. 
 
. § 
 
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