THE SKELETON. 29 



the neck. They have on the upper surfiice long processes, which 

 proceed upwards and backwards, forming the withers ; these 

 I)rocesses gradually inci'case in length from the first to the fifth *, 

 when they gradually decrease to the twelfth or thirteenth, and 

 then continue the same. Each dorsal vertebra is connected, 

 by means of a joint, with two ribs, of which there are usually 

 eighteen pairs in the horse. 



The lumbar vertebra? are five, and sometimes six, in number, 

 and differ from the other vertebrce from havins; nuich longer 

 lateral processes; but their spinous processes are somewhat 

 shorter than those of tlie back. The lateral processes serve, in 

 some measure, to supply the absence of the ribs, giving support 

 on their upper surfaces for the strong muscles of the loins, and 

 below forming a roof for the protection of the abdominal viscera. 

 When we see a horse with a very light carcass these transverse 

 processes are usually very short. 



These bones compose the spine, but the spinal cord is con- 

 tinued through the sacrum or rump bone, which, in the youn"^ 

 subject, is composed of five separate pieces, like the lumbar ver- 

 tebrae, but in the adult is consolidated into one bone, and 

 forms a roof for the pelvis, and a protection for its contents. 

 At the extremity of the sacrum the bones of the tail, about 

 eighteen in number, called the ossa coccygis, begin. The 

 sacrum is slightly arched, so as to afford greater room below, 

 and its spinous processes differ from those of the loins in sloping 

 in an opposite direction. 



The Pelvis, so called from its resemblance to a basin, is an 

 irregular cavity which contains the urinary and genital organs, 

 and is formed by the sacrum and the ossa coccygis above, and the 

 two ossa innominata, or haunch bones, on each side and below. 

 In the foetus this bone is composed of three separate pieces, the 

 ileum., the ischium, and the pubes. The ileum is the largest 

 division, forming the upper and anterior part of the bone, and 

 those visi!)le projections in the horse, the hips, at the sides, and 

 the part above close to the sacrum, which projects so much in 

 goose-rumped horses, as they are called; the ischium is the part 

 Avhich projects backwards, and the pubes the portion which joins 

 inferiorly the corresponding part on the other side, the union 

 forming the symphysis pubis. All these separate pieces unite 

 in forming the socket into which the first bone of the hind ex- 

 tremity fits, thus composing the hip joint. 



Tlie Bones of the Fore Extremity. 



A superficial observer would be apt to imagine that animals 

 differ from each other and from man, and from birds, in 



* These bones ai-e often diseased in fistulous withers. 



