DIGESTION IN THE MOUTH. 283 



The diastatic power of the submaxillary saliva varies very con- 

 siderably in different animals. It is active in all the herbivora, with the 

 exception of the rabbit and guinea-pig. In the sheep the submaxillary 

 saliva is more active than that of the parotid, while it is faintly active in 

 the horse, and is almost inactive in the dog when freshly secreted. The 

 general characteristics of the submaxillary saliva vary in different 

 animals under different conditions, and are therefore subject to much con- 

 tradiction. The secretion reaches its excess during mastication follow- 

 ing prehension of food. It is suspended entirely during the mastication 

 of rumination (Colin, Ellenberger, and Hofmeister), — a fact which is 

 very remarkable when it is recollected that the chemical stimulation 

 of the nerves of taste must be then much more marked than in the 

 hurried first mastication. The submaxillary glands are also nearly 

 quiescent in the intervals of rumination ; its secretion is called forth by 

 pilocarpine injections, but to a less degree than in the case of the 

 parotid. 



It seems almost incomprehensible that the submaxillary, which 

 during rumination remains quiescent, should secrete actively during the 



B 



Fig. 118.— Sublingual Gland of the Ox. (Colin.) 

 A, submaxillary duct ; B, inferior duet of the sublingual gland ; C C, superior sublingual ducts. 



mastication of a tasteless foreign body, such as a piece of string or wood 

 (Ellenberger). This fact can scarcely be explained but by supposing 

 that the products of fermentation occurring in the rumen exert an in- 

 hibitory influence on the secretory nerves of the submaxillary glands. 

 Its principal function seems to be to assist in the appreciation of the 

 sense of taste, and to act as a lubricant to aid in the first deglutition. 



3. The Sublingual Secretion.— The collection of pure sublingual 

 saliva is accomplished in the same way as the submaxillary, although in 

 general it is more difficult, excepting in the case of the ox, where the large 

 size of the duct renders the operation very easy. In most animals, 

 however, it is extremely difficult to obtain it in a state of purity, as the 

 gland, especially in the ox, has a number of excretory ducts (Fig. 118). 

 The characters of sublingual saliva may partially be determined by 

 preventing the parotid and submaxillary secretions from entering the 

 mouth by ligating their ducts, and then collecting the fluids in the mouth 



