THE HEAD AND NECK 



09 



vidua! bones, but every ridge and surface for the 

 attachment of muscles, and every hole for the passage 

 of artery or nerve, seen in the one can be traced in 

 the other. Yet they differ remarkably in general 

 aspect. The difference mainly lies in this : in man 

 the brain-case is very large and the face of relatively 

 minute proportions. In the horse, on the other hand, 

 the brain is extremely reduced, and the face, especially 

 the mouth, of enormous size. In other words, the 

 characteristic form of man's head is chiefly due to his 

 great brain, that of the horse to the comparatively large 

 development of the apparatus for masticating his food. 



Taking the different regions of the horse's skull 

 (fig. 16) into closer consideration, and beginning at the 

 hinder, or ' occipital ' end, we may observe the rounded, 

 almost polished surface of the condyles (oc), already 

 mentioned, which, fitting accurately into the correspond- 

 ing depressions of the atlas, and in life covered with a soft, 

 perfectly smooth layer of cartilage and lubricated with 

 synovial fluid, allow the head to move freely up and 

 down, or sideways, even when the neck is fixed. The 

 same region also shows various roughened, projecting 

 ridges or promontories for the attachment of the power- 

 ful ligaments and muscles required to support and move 

 so heavy a head, projecting forwards at the end of so long 

 a neck. Above, on each side, are the 4 occipital crests,' 

 joining in the middle line to form the c occipital pro- 



h 2 



