THE SKELETON 



47 



over which sheep pass and thus assists members lost from the flock 

 to trace their fellows. It is also thought that the secretions are 

 waste products which if not eliminated will cause inflammation and 

 lameness. The likelihood of plugging the hole in the foot and thus 

 preventing the escape of the secretions is regarded as one important 

 reason why sheep should not be made to walk through mud. 



In sheep, the foot glands are present in all four feet. They are 

 usually absent in goats, but sometimes small glands appear in the 

 fore feet. 



FIG. 17. The interdigital pouch. (From "Sheep and Its Cousins," Lydekker. Courtesy 

 of E. P. Button & Co.) 



The Skeleton. 2 The vertebrae forming the spinal or vertebral 

 column are grouped as follows: 7 cervical, 13 dorsal or thoracic, 6 

 to 7 lumbar, 4 to 5 sacral, and 3 to 24 coccygeal. The last are not 

 perfect vertebrae, as the spinal canal does not extend through them 

 (Fig. 18). 



With the exception of the cervical vertebrae all of these groups 

 vary in the number of bones they contain. There are usually 13 

 vertebras in the thoracic group, but occasionally there are 14, and 

 more rarely, only 12. In the lumbar group the occurrence of 7 

 vertebrae is almost as frequent as 6, but the reduction to 5 seldom 

 takes place. Seyffurth indicates that there may be 4 or 5 sacral 



2 See Sisson, " The Anatomy of the Domestic Animals," 1914. 



