DIGESTION IN THE MOUTH. 293 



pected from the fact that raw starch requires several minutes' contact 

 with the saliva of the horse to be converted into sugar. It is not to be 

 therefore concluded that the amylolytic power of the saliva is of no 

 practical value, since it will be found that in the horse the chemical 

 action of the saliva may continue in the stomach. 



In the ruminants the diastatic action of the saliva is probably about 

 the same as that of the horse, but the conditions for the conversion of 

 starch into sugar are more favorable, since the saliva is constantly being 

 secreted, constantly swallowed and carried to the rumen, where it meets 

 with the most favorable conditions for acting on the starch — in other 

 words, an alkaline medium considerably diluted and an elevated tem- 

 perature. 



Of the other animals, the following series represents the diastatic 

 action of the saliva, it being most marked in the first animal and least in 

 the last : hog, rat, rabbit, cat, dog, sheep, and goat. In all the domestic 

 animals the parotid saliva possesses the highest degree of amylolytic 

 power. The orbital gland of the dog appears to produce no amylolytic 

 ferment. All the so-called antiseptics and stronger chemical agents pre- 

 vent the action of the salivary ferment. The duration of the action of 

 human saliva on raw starch before the presence of sugar can be detected 

 is as follows : On potato-starch, after two to four days. ; on starch from 

 peas, after one and one-third to two hours ; on wheat-starch, after one-half 

 to one hour; on barley-starch, after ten to fifteen minutes ; on oat-starch, 

 after five to seven minutes ; on rye-starch, after three to six minutes ; on 

 corn-starch, after two to three minutes. 



If raw starch is finely comminuted, as by grinding with powdered 

 glass, the time of the reduction is considerably reduced. 



Extracts, or the secretion of the different salivary glands in the 

 domestic animals, are entirely inert on fats, proteids, and cellulose. 



7. The Mechanism of the Salivary Secretion. — The numerous inves- 

 tigations which have been undertaken to explain the mechanism of salivary 

 secretion have yielded results of far more importance than that which 

 they possess as bearing upon the secretion of saliva alone. It is from the 

 results of these experiments that has been deduced all our knowledge of 

 glandular secretion, its dependence upon the nervous system, and its rela- 

 tion to the circulation. In the case of the saliva it has already been men- 

 tioned that, under ordinary circumstances, in all animals the secretion of 

 the saliva is either remittent or intermittent. In other words, as a rule 

 but enough saliva is poured into the mouth during abstinence to keep the 

 surfaces moist. "When, however, food is taken into the mouth and the 

 process of mastication commenced, or in the ruminant animal during 

 the process of rumination, the secretion of the salivary glands is at once 

 greatly increased in activity. Further, allusion has been made to the fact 



