172 PHYSIOLOGY AT THE FARM. 



of the parotid, a colourless, limpid, tasteless, and inodorous 

 fluid, devoid of all morphological elements, such as epithelium - 

 plates and mucous corpuscles. Its specific gravity is 1.0041 ; 

 it has less of an alkaline reaction than the secretion of the 

 parotid ; it contains less lime in combination with organic 

 matter, and therefore attracts less carbonic acid from the air 

 than the parotid secretion ; in other respects it contains the 

 same constituents, including the sulphocyanide of potassium. 

 The ratio of the inorganic to the organic matter is 66.2 to 

 33.8 ; while that ratio in the parotid secretion is as 70.2 to 

 29.8. The secretion of the submaxillary gland differs from 

 that of the parotid in being viscid, so that it can be drawn out 

 into threads. The effect of the mixed saliva to convert starch 

 into sugar, belongs to that form of saliva in the dog as well as 

 in man and the vegetable-feeders. One point of doubt remains, 

 namely, whether the saliva, as taught by Liebig, conveys 

 oxygen into the stomach to aid in the process of digestion. 



Lips. The lips in the dog offer no striking peculiarities. As 

 in the horse, the lips serve to gather together the food, and to 

 convey it to the mouth. The orbicular muscle which closes the 

 lips forms the main substance of the lips, as in similar animals, 

 being attached to no bone, while the other labial muscles take 

 their attachment from the adjacent bones, and perform various 

 movements by their contraction, in obedience to the ordinary 

 law of muscular action, that the more movable part then ap- 

 proaches to the more fixed. The lips in the dog are covered, as 

 in other such animals, by mucous membrane, and are every- 

 where freely studded with follicular glands, which secrete 

 abundantly. 



Cheeks. The cheeks in the dog consist, as in other quadru- 

 peds, of a cutaneous, a muscular, and a mucous layer. They 

 form the sides of the mouth, and close the interval between the 

 two jaws. The principal muscle is that termed buccinator, as 



