22 PHYSIOLOGY AT THE FAEM. 



development of the salivary glands appear to equal that in 

 solidungulous animals, of which order the horse is one. 



The saliva has an especial effect on starch. When saliva or 

 a portion of the salivary glands, or even a little dried ptyaline, 

 is added to starch-paste, the starch" is very rapidly trans- 

 formed into dextrine and grape-sugar. One use of the saliva 

 then, may be to assist in the transformation of the starch 

 of the aliment that being naturally insoluble into soluble 

 dextrine and grape-sugar, so as to be rendered more fit for 

 absorption. 



Lips. The lips are attached to the respective alveolar projec- 

 tions of the superior and inferior maxilla by the muscles which 

 move them, by the areolar or cellular tissue contained in their 

 substance, and, finally, by the lining membrane. The lips ex- 

 hibit externally perpendicular lines of division, have little papil- 

 lary eminences on their surface, and show a soft and short coat- 

 ing of hair, out of which spring several long, straggling, strong 

 hairs or whiskers. The lower lip is smaller and thinner than 

 the upper, and has near its centre a tuft of coarse hairs, com- 

 monly called the beard. The orbicular muscle, or muscle which 

 closes the mouth, being free from any direct attachment to 

 bone, is properly regarded as forming the main substance of 

 both lips. The other muscles which enter into the lips are 

 attached to adjacent bones, and determine the other move- 

 ments of the lips in accordance with the usual rule of muscular 

 action. There are numerous glandular bodies, termed fol- 

 licular glands, spread over the mucous membrane which invests 

 the lips. The lips are possessed of great sensibility. With 

 his lips the horse, as with a hand, gathers up his corn, and 

 with them collects together the grass before he divides it with 

 his nippers. 



Cheeks. The cheeks constitute the sides of the mouth clos- 

 ing the interval between the two jaws. They consist of a 



