292 Zoological Society. 
other quadrupeds, e. g. the larger Carnivora, is metamorphosed into 
the yellow elastic tissue—tissu jaune—in the Aurochs, as in the 
common Ox, and in a still greater degree in the Rhincceros and 
Elephant. By this change the abdominal muscles are proportionally 
relieved or aided in the sustentation of the capacious and heavily- 
laden digestive reservoirs. 
In the Aurochs, as in the other Ruminants, the disposition of the 
omental sac upon the sternal aspect of the paunch, interposed between 
it and the abdominal walls, makes it perform the office of a serous 
articular sac, two smooth and lubricated surfaces—the inner ones of 
the sac—being apposed to each other, and easily and freely gliding 
on each other; it is like a kind cf great ‘tunica vaginalis ’"—facili- 
tating the spiral peristaltic movements of the paunch, and by the 
layer of fat tending to preserve the warmth of the paunch. 
The skeleton of the Aurochs has been well delineated by Bojanus, 
in connection with an outline of the entire animal, and by Mr. George 
Landseer separately. The general characters of the framework of this 
rare species are very accurately rendered in both these figures. The 
skeleton of the young male Aurochs showed the same characteristic 
elevation of the spinous processes of the anterior dorsal vertebre, 
and the same characteristic number of ribs—fourteen pairs—which 
are shown in the above-cited figures, and which repeated examina- 
tion has established as constant peculiarities of the species. With 
regard to the lengthened spines, I shall only remark on this inter- 
esting morphological peculiarity, that it contributes to illustrate the 
artificial nature of that view of the part commonly called rib, or ver- 
tebral rib, as a bone or element of the skeleton, apart from or be- 
longing to a distinct genus from the other vertebral elements. This 
view originally arose from the contemplation of the proportions of 
the ribs or pleurapophyses and spinous processes as they exist in Man. 
A long and slender form is associated with the idea of a rib as an 
essential character. In the Aurochs we see that the vertebral ele- 
ment called neural spine is longer than the pleurapophysis in the 
second and third dorsal vertebree. But it is anchylosed to the other 
vertebral elements, whilst the pleurapophyses retain their primitive 
freedom, and the dorsal vertebrz are characterized as ‘ articulating 
with the ribs.’ This, however, is a periodic, not an essential character. 
At an early period of life the cervical vertebre also articulate with 
ribs, 2. e. pleurapophyses ; but these become broad and remain short, 
and coalesce with the centrums and diapophyses of their respective 
vertebre ; and the anthropotomist then calls them ‘ transverse pro- 
cesses, and distinguishes them as being perforated, the foramen 
being the space included between the centrum, the diapophysis, and 
the pleurapophysis. 
Another remark is suggested by the skeleton of the Aurochs, 
touching the true value of the character of its fourteenth pair of free 
pleurapophyses. In the genus Bos proper there are only thirteen 
pairs. In the American Bison there are fifteen pairs. According to 
the artificial character in anatomy of the ‘ dorsal vertebrz,’ the above- 
