EFFECTS OF VARIATIONS IN SKELETAL STRUCTURE 49 



forward of the coccygeal group. When a sheep is unusually long 

 in the middle, speculation as to whether it possesses an extra rib is 

 quite justifiable, and if the space between the last rib and the junc- 

 tion of the ilium (hip bone) with the spine is abnormally wide there 

 is basis for assuming that there is an extra vertebra in the lumbar 

 group. If, on the other hand, the sheep has a short middle and if 

 the space from the last rib to the hip is also very short, it may be 

 that the lumbar vertebrae are reduced to 5 in number (Fig. 19). 



Fig. 19. — A long and u short sheep, illustrating the probable variation in the number of 

 vertebra in the spinal column. 



Aside from the variations noted, litiAe is known of how much 

 sheep vary in skeletal arrangement. Judging from exterior form, 

 some individuals seem to carry a wider and higher arch to their 

 ribs than others, but just how much of the difference is due to 

 thickness of flesh and fat, and how much to the actual shape of the 

 ribs has not been definitely determined. The processes extending 

 upward from the vertebrae in the region of the shoulders seem longer 

 in some sheep than in others, or else the top of the blade is set lower 

 down, for in certain instances the spinal |)rocesses are so prominent 

 that any amount of fattening will not cover the shoulder top. In 

 practically every improved breed there are occasional specimens 

 4 



