272 AMYLOLYTIC POWER AND CHEMICAL 



as in the content of solid matter under the influence of the 

 stimuli. It is thus safe to assert that alcohol and alcoholic 

 fluids not only stimulate the flow of saliva, but that they also 

 tend to increase the concentration and amylolytic power of 

 human mixed saliva, results which are in close accord with 

 the action of these fluids upon the secretion of the sub-maxil- 

 lary saliva of the dog.* Further, simple mechanical stimula- 

 tion, as mastication, may also increase the amylolytic power of 

 mixed saliva. Lastly, it should be mentioned that the saliva 

 resulting from the above forms of stimulation, excepting 

 mechanical stimulation, is much more viscid than the fluid 

 secreted spontaneously, evidently from a higher content of 

 mucin. 



SUMMARY. 



Human mixed saliva contains normally no sodium carbonate 

 whatever ; the alkalinity indicated by litmus, lacmoid, etc., is 

 due to hydrogen alkali phosphates, with possibly some alkali 

 bicarbonate. Mixed saliva invariably reacts acid to phenol- 

 phthalein. 



The alkalinity of mixed saliva, as indicated by lacmoid, is 

 greater before breakfast than after the morning meal ; a 

 conclusion which stands in direct opposition to the statement 

 frequently made that " the alkalinity (of mixed saliva) is least 

 when fasting, as in the morning before breakfast, and reaches 

 its maximum with the height of secretion during or immedi- 

 ately after eating." f 



Saliva secreted after a period of glandular inactivity, as before 

 breakfast, manifests greater amylolytic power than the secretion 

 obtained after eating, as observed by Hofbauer. Correspond- 

 ing with this increase in amylolytic power occurs an increase 

 in the proportion of alkaline-reacting salts, but the increased 

 amylolysis is due primarily to an increase in the amount of 

 active enzyme contained in the saliva. 



Mixed saliva, whether collected by mechanical stimulation 



* See Chittenden, Mendel, and Jackson, Amer. Jour. Physiol., 1898, i, p. 167 

 t Text-book of Physiology, edited by E. A. Schafer, 1898, i, p. 344. 



