140 PHYSIOLOGY AT THE FARM. 



of the cheek, and by the simultaneous contraction of these 

 muscles on the opposite sides the cavity of the mouth is dim- 

 inished. 



Lower Jaw. The lower jaw in the sheep has very much 

 the same characters as in the ox. The proportions between 

 the ascending and the horizontal portions are very much the 

 same. The height of the ascending portion equals nearly half 

 the length of the horizontal portion. The coronoid process, 

 which is long and narrow, and curved upwards and backwards, 

 is situated immediately before the articular surface. The con- 

 dyloid process is more than twice as broad from without in- 

 wards as from before backwards. Its central part is somewhat 

 concave its lateral parts convex. The horizontal portion of 

 the jaw is slightly contracted in front of the molar teeth, 

 from above downwards and from within outwards ; it becomes 

 thicker again more forwards, where it supports the incisor 

 teeth, uniting itself to its fellow of the opposite side at an 

 acute angle. 



The motions -of the lower jaw in the sheep correspond very 

 closely with those of the same bone in the ox : the lateral 

 motion is very conspicuous, as concerned in the slow grinding 

 process to which the semi-dissolved aliment is subjected in 

 rumination. 



Pharynx. The pharynx that is, the expanded upper part 

 of the alimentary canal a funnel-shaped muscular bag, lined 

 with mucous membrane, and attached to many adjacent parts 

 by muscular fibres, has very much the same character in quad- 

 rupeds like the sheep as in man. For the most part, however, 

 its muscularity is proportionately greater than in man, owing 

 probably to the superior force required for deglutition in the 

 position of their bodies, in which less aid is derived from 

 mere gravitation. In the first stage of deglutition (p. 31), the 

 masticated food is collected on the tongue and pressed back- 



