cast of the whole cerebral surface was secured. Before the brain was in any way disturbed from its natural position, the relation of the posterior lobes of the cerebrum to the cerebellum was carefully observed, and the ten persons present, anatomists and naturalists, were unanimous in declaring that the former projected backwards over the latter a quarter of an inch. In the removal of the brain, the disposition of the membranes and nerves was observed to be strikingly similar to the corresponding human parts. The arterial circle of Willis was quite human. The entire encephalon, with arachnoid and pia mater, vessels and nerves attached, and as much of the spinal cord as could well be reached by an ordinary scalpel, was carefully removed, and its weight was found to be 13 ounces and 6 drachms; from this 6 drachms must be deducted on account of injection matter in the larger vessels, which will make the proportional weight of the brain to that of the whole body very nearly as 1 to 20. The three great lobes of each cerebral hemisphere were seen well developed; the two anterior lobes formed together a blunt projection forwards on the median line, whilst beneath, their inner borders projected downwards as ridges; the under surfaces of these lobes were distinctly concave; the middle lobes were more prominent downwards than in man, and the projection of the posterior lobes beyond the cerebellum was as decided as before. After the brain had been for three days in spirits, the cerebral hemispheres measured in length 48 in.; in breadth across the middle or widest part, 3 in.; the greates twidth of the cerebellar hemispheres being 23 in.; so that the cerebellum is markedly overlapped, laterally as well as posteriorly, by the posterior lobes of the cerebrum. The convolutions of the cerebral hemispheres were numerous, somewhat intricate, and partially symmetrical; two main sulci-traceable, one from the Sylvian fissure, the other from the under surface at the back of the crura cerebri-appeared to mark out even on the top of the hemispheres the division into anterior, middle, and posterior lobes. The island of Reil was quite evident. The corpus callosum, 1 in. in length, showed, as in man, distinct though minute transverse striations, and a longitudinal raphe, formed of two slightly raised lines and an intervening groove. A section of the right hemisphere to expose the lateral ventricle showed as bold and as numerous projections of the external sulci into the white centrum ovale as are commonly seen in the human cerebrum. The ventricle itself was beautifully distinct, its anterior cornu curving boldly outwards in front of the striated body; its middle cornu winding outwards and downwards to the very bottom of the large middle lobe, and containing the hippocampus major with its pes, corpus fimbriatum and choroid plexus; and its posterior cornu extending in an ample curve backwards and inwards, so as almost to touch the grey matter of the surface next the median line, and having within it, on its floor and inner side, the projection called hippocampus minor very distinctly marked. On the floor of the body of the ventricle were to be seen the corpora striata, the tæniæ semicirculares and the free edge of the fornix, with the choroid plexus; these last rested on the velum interpositum, which covers the third ventricle and the optic thalami, quite as in man. Further investigation in this direction was not made, as it was thought desirable to preserve, for after inspection, the parts already enumerated. The fourth ventricle, as it is called, and its walls, as they could be examined without injury, were inspected; the cavity was closed behind, and had its small choroid plexus, after the human pattern; a second similar, but smaller, plexus existed on each side, just outside of the ventricle, and attached to the cerebellum. The point of the calamus scriptorius was well defined, but no white lines of origin of the auditory nerve were distinguished; on the other side of the medulla oblongata the usual nerve swere met with, and also the pyramids and olivary bodies, which were not very prominent; they were not further examined. The cerebellum was laminated, and had the great human divisions; on examining that part which overhangs the medulla oblongata, the inferior vermiform process, the uvula and tonsils, the flocks, and other parts enumerated in human anatomy, could, without difficulty, be dissected out; the superior vermiform processes also were evident on raising carefully the posterior lobes of the brain. The conclusions from these short and imperfect notes are those which have already been made public by Professor Huxley-viz. 1st, that the Chimpanzee is not, properly speaking, quadrumanous, but that it possesses four prehensile extremities, two hands, namely, and two feet; and, 2nd, that the brain of the Chimpanzee differs from the brain of man only in size and weight; therefore, in the smaller size and extent of its cerebral convolutions; the same parts without exception existing in both brains. Whether the cerebral matter of the ape differs from that of man in microscopic characters or how otherwise it may differ, are problems yet to be worked out. 259 XXXIX.-NOTE ON THE NUMBER OF THE CERVICAL VERTEBRÆ IN THE SIRENIA. By W. H. Flower, Conservator of the Museum of the Royal College of Surgeons. In a recent number of the Sciences of St. Petersburg, Bulletin of the Imperial Academy of Professor Brandt has published the following interesting remarks on the number of the cervical vertebræ in the different known forms of the Order Sirenia. "It is commonly stated that in the genus Manatus, also, according to Steller, occasionally in Rhytina, there are only six cervical vertebræ, instead of seven, the usual number in the other mammalia. Blainville (Ostéogr. Manatus, p. 49) opposes this opinion. He thinks that one of the vertebræ (the sixth) is lost in Manatus; its body disappearing, its arch alone remains in the flesh, with which it is removed in the preparation of the skeleton. He lays particular weight on the fact that, in the Dugong, there are quite distinctly seven neck-vertebræ, and he states that he has seen the same number in a skeleton of Manatus australis. But he gives no further proofs in support of this view, although they appear very necessary for the refutation of the opinion that there are but six cervical vertebræ, accepted by Daubenton, Cuvier, A. Wagner, Schlegel (see my Symbol. Sirenolog. Pars I, p. 96), Stannius and other distinguished naturalists. He also omits to refer to the fact that already Al. v. Humboldt, E. Home and Robin have attributed seven neck vertebræ to the Lamantin. "As Steller accepts in the Rhytina also only six neck vertebræ, and as my osteological studies thereon aim at a comparative osteology of all living genera, I was obliged in them to express myself, though briefly, upon the number of the neck-vertebræ in the genus Manatus (see Symbol. Sirenol. P. II. p. 45). I certainly had at my command only one, though a very well preserved, skeleton of the Manatus latirostris, which I believe, however, to be sufficient to enable me to supply a contribution to the neck-vertebra question. "As to the Rhytina, there can be no doubt whatever of the necessity of ascribing to it seven neck-vertebræ, as has been done by Giebel. The head of the first rib articulates by means of its anterior half with a fossa on the body of the seventh cervical vertebra, and * Bermerkungen über die Zahl der Halswirbel der Sirenien. Bull. Acad. St. Pet. v. p. 7. its tuberosity is so closely attached to the strong transverse process of the same vertebra that it might, though only on superficial observation, be taken, as it was by Steller, for a dorsal vertebra, and thus only six neck-vertebræ might be ascribed to the Northern Sea Cow. When it is considered that not only in Halicore, but also in the Pachyderms and most Ruminants, the anterior part of the head of the first rib articulates with a fossa on the seventh cervical vertebra, its similar relation in Rhytina presents nothing surprising. I am nevertheless inclined to regard the intimate connection of the anterior surface of the first rib with the transverse process of the seventh cervical vertebra as an approach towards Manatus, and to consider Rhytina, in this respect, if not altogether, intermediate between Halicore and Manatus (see my memoir in Bulletin Sc. T. iv, 1861, p. 304-305, Melang. biol. T. iv. p. 75-77, and Spicileg. Sirenol. P. ii. p. 46-48). "In Manatus, the deviation in the articulation of the first rib is carried to a still further degree, as compared with Rhytina. Its head has no union with the eighth vertebra from the skull, corresponding to the first dorsal vertebra of other mammals, but its anterior half articulates with a fossa on the body of the sixth cervical vertebra, which thus, in this respect, represents functionally the seventh cervical vertebra of Halicore and Rhytina. The posterior half of the head of the first rib articulates with a fossa on the body of the seventh vertebra from the skull, whilst its tuberosity contracts a moveable union with an articular surface on the transverse process of the same vertebra. "In respect to function, therefore, the vertebra in question corresponds to a dorsal vertebra, the first of the series. In its construction, especially in the form of its narrow body and arch, it appears as one of the cervical vertebræ, among which, from its numerical position, according to the standard of other mammalian skeletons, it might also be counted. "If, then, we attach a greater importance to its functional nature, the seventh vertebra from the skull of the Manatee may be regarded as the first dorsal vertebra, and indeed the more so, as the rib connected with it is the first of the two united with the sternum, therefore a true rib. According to this view, the Manatus would possess only six neck vertebræ, and would thus form among the mammalia a well-founded exception, established since the time of Daubenton, and lately also brought forward by Stannius. 1 "Such an exception, however, does not agree with the construction of the skeletons of other mammalia, or with the form, the small size, the number, and the situation of the vertebra in question. It may further be observed that also in Birds and in Bradypus ribbearing cervical vertebræ are present; cervical vertebræ may therefore perform the function of dorsal vertebræ. We might, then, consider the peculiar condition of the seventh vertebra as a simple anomaly, so that it still might be looked upon as a cervical vertebra. Such a view would have the advantage of bringing a greater (even a general) agreement in the number of the cervical vertebræ of the Mammalia, whilst the first view certainly agrees better with physiological ideas, and moreover can make claim to the nulla regula sine exceptione." To these remarks of the learned Academician of St. Petersburg (whose studies on the Order Sirenia are so well known and appreeiated) I venture to add a few notes. The consideration of this remarkable exception to the ordinary number of the cervical vertebræ in the Mammalia receives some illustration from the analogous case of the three-toed sloths (genera Bradypus and Arctopithecus). Upon the number and character of the neck-vertebræ of these animals, we have two excellent memoirs, one by Mr. Bell,* and the other by the late Mr. H. N. Turner.† In the first, the interesting discovery of small moveable ribs attached to the eighth and ninth vertebræ was announced, and it was thence concluded that these must belong to the dorsal series. Mr. Turner, however, sums up the whole characters by which the so-called cervical and dorsal vertebræ in the Mammalia generally are distinguished from each other (not forgetting that the distinction is rather for the convenience of the anatomist in description, than absolutely fixed by nature), and proves, to my mind conclusively, that the eighth and ninth vertebræ of the sloth are, in all their morphological characters, the homologues of the sixth and seventh of the ordinary mammal, and as the atlas and axis undoubtedly correspond in both cases, there must be an interposition of two additional vertebræ somewhere about the middle of the series. Apart from that derived from the actual character of the bones * Trans. Zool. Soc. vol. i. p. 113. |