Digestion. 1<> ; ~> 



is nearly, though not entirely, lost. Ellenberger's observa- 

 tions are so reliable that we are bound to accept as a fact 

 that at some period of digestion horse saliva may possess 

 amylolytic properties. 



Meade Smith* states that the saliva of the horse will 

 convert crushed raw starch into sugar in fifteen minutes, 

 and that the process will continue in the stomach (where 

 the early acidity, according to Ellenberger, is due to lactic 

 and not hydrochloric acid) ; he further states that horse 

 saliva will convert cane into grape-sugar. In ruminants 

 he believes the starch conversion takes place both in the 

 mouth and rumen. 



Though I do not accept these views, we shall shortly 

 show how starch is converted into sugar in the horse's 

 stomach. 



Secretion of Saliva. — The mechanism concerned in the 

 secretion of saliva deserves our careful attention, for the 

 reason that it throws considerable light on other secretory 

 processes. It has been worked out by so many competent 

 observers that the leading points in its action are beyond 

 all doubt. The submaxillary gland of the dog has afforded 

 the desired information, and we have reason to believe that 

 the same process holds good for the parotid and other 

 glands, both of this animal and herbivora. 



The chief point in the secretion is that it is controlled by 

 the nervous system, and is independent of the blood pres- 

 sure in the gland. Afferent nerves, viz, the gustatory 

 division of the fifth and the glosso-pharyngeal, convey from 

 the mouth to the medulla a certain sensation, which by 

 means of an efferent nerve is conveyed to the gland and 

 secretion results. The efferent nerve of the submaxillary 

 gland of the dog is supplied by the chorda tympani, a small 

 branch given off' by the seventh cranial nerve which enters 

 the gland at its hilus, and supplies the vessels with dilator 

 and the cells with secretory fibres. How the nerve ter- 

 minates in the gland is unknown. The second nerve supply - 



* ' A Text-book of Comparative Physiology.' 



