362 JUDGING FARM ANIMALS 



spines of different races of sheep. According to Sissoii 2 

 there are commonly seven cervical vertebrae, thirteen tho- 

 racic and six lumbar vertebrae. The sacrum usually consists 

 of four parts, and the bones in the coccyx, at the end of 

 the spinal column, vary from three, in short-tailed sheep, 

 to twenty-four or more. There are usually thirteen pairs 

 of ribs, but fourteen are not uncommon. The ribs are nar- 

 rower, and the front ones are more strongly curved, than 

 is the case with the ox. The skulls of sheep and ox are 

 quite similar, but the former is more pointed at each end, 

 with the frontal bones at the eye rather prominent. It is 

 this small size of the end of the skull, at the muzzle, that 

 enables the sheep to graze so close to the ground. Lydekker 

 states 3 that, "the skulls of tame sheep differ from those 

 of their wild relatives when specimens with the same ap* 

 proximate basal length are compared by the smaller di- 

 ameter of the socket of the eye, the abortion of the auditory 

 bulla 4 at the base of the skull, and the much smaller ca- 

 pacity of the brain chamber. It has been shown, for 

 instance, that whereas in the wild mouflon the brain capac- 

 ity ranges from 130 to 170 cubic centimeters, with a mean 

 of 140 cubic centimeters, in domesticated sheep, having 

 skulls of the same average size, the mean brain capacity is 

 only from 110 to 120 cubic centimeters. These differences are 

 due, of course, to the more or less protected conditions under 

 which domesticated sheep pass their existence, thereby re- 

 ducing the need of acuteness in the senses of hearing, sight 

 and smell." The humerus or large bone of the arm is 

 relatively longer and more slender than it is with the ox, 

 and the same applies to the bones of the forearm. The 

 ischium, or what is often called the pin bone, at the end of 

 the pelvis on each side of the tail, according to Sisson, 5 

 slopes downward and backward, and forms a much larger 

 angle than in the case of the ox. This may account in part 



2 The Anatomy of the Domestic Animals, 1914, p. 156. 



3 Sheep and Its Cousins, p. 21. 



* A prominence below the opening of the ear in the skull of many animal 

 6 Ibid., p. 160. 



