1S80.] VARIATION IN EClUUS ASINCS. 3 



generally short, although we have seen it long and connected with 

 the first rib below the upper head of scalenus by an elastic band ; 

 and in a specimen now before us the transverse processes are asym- 

 metrical, several inches in length, prolonged by well-marked elastic 

 bands to cartilaginous nodules appended to the prosternum in front 

 of the first sterno-costal articulations. 



Dorsal and Lumbar. — The dorsal intervertebral gaps are some- 

 times truly intervertebral ; often each is wholly pierced through the 

 })edicle of one vertebra. The degree of separation of the costo-trans- 

 verse articulation from that for the head of the rib varies much in 

 the posterior dorsal vertebras of different individuals. The last ribs 

 also vary much in length, size, and degree of curvature. The pre- 

 sence of a so-called "floating rib," making the series nineteen in 

 number, is frequently observable. This "floating rib'' is generally 

 present only on one side. It is not a vertebral rib, but a sternal rib ; for 

 it is appended to the extremity of one or two lumbar transverse 

 processes, the homotypes of the vertebral costse of the dorsal region. 

 Often, when not represented by bone, it occurs as a portion of cartilage 

 or a band of white fibrous tissue, embedded in the abdominal mus- 

 cles in such a manner as to remind us of the homotypical concor- 

 dance of the intercostals and the abdominal muscles. 



In the sacral region it is often difficult to define the extent of the 

 '•false sacrum" backwards; for coccygeal vertebrae become appended 

 by ankylosis, increasing apparently the ordinary number of five 

 sacral bones. The last lumbar, too, sometimes assists in the sup- 

 port of OS innominatum; and in other respects the "true sacral 

 bones" are not always the same. 



Coccygeal. — Vary in number, especially with age. 



The peculiar modifications which we have noted in the seventh 

 ceiTical, the uncertainty observable in the anterior and posterior 

 parts of the lumbar and sacral regions, and the variation in the 

 number of ribs prominently bring to our mind the question "How 

 is the vertebral column becoming modified in the present day?" and 

 also, " Will an examination of these points throw any light on the 

 remarkable preponderance of dorso-lumbar vertebrae and costae in 

 Perissodactyla ungulata ? " 



S/cull. — Exhibits many minor variations, most of them probably 

 sexual or due to age. 



Limbs, Fore. — Scapula : differences in figure, thickness etc. 

 Often, instead of the gradual disappearance of the spine inferiorly, it 

 terminates in a slightly prolonged process, a rudimentary acromion 

 similar to that seen in the Ox, but smaller. Medullary foramen 

 varies in position ; also glenoid cavity rounded or oval. 



Humerus : synovial fossettes vary in size and form, as do those in 

 upper part of radius and ulna.- The ulna generally extends down- 

 wards only two-thirds of the length of the radius ; but in the foetus it is 

 much longer in proportion, and in the adult we occasionally find it 

 passing downwards to the supero-external part of the knee to arti- 

 culate with OS cuneiforme. If we examine the inferior extremity of 

 the radius of the fcetal colt, we may note that at its external part is 



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