WATER AS A DIETARY CONSTITUENT 281 



food was invariably masticated without the aid of .water. Let us follow 

 the various activities of the digestive tract, from mouth to anus, and see 

 the actual influence of water taken with meals upon these activities. 



Influence on Salivary Digestion. It is not necessary to believe with 

 Bunge that the main function of the saliva is one of lubrication, in order 

 to show that the presence of water aids salivary digestion. The following 

 table (Bergeim and Hawk) shows that the dilution of saliva with water 

 facilitates the action of the salivary amylase: 



EFFECT OF DILUTION OF SALIVA IN CONCENTRATED MIXTURES 

 Diluent: Filtered tap water. Time of digestion: 10 min. Temp.: 0. 



The diluent in the above experiment was ordinary tap water, and 

 the optimum dilution was six volumes of water. 



Influence on Gastric Digestion. (Stimulatory Power of Water). 

 The most severe indictment brought against the drinking of water with 

 meals was the claim that water thus taken would dilute the gastric juice 

 and hence delay digestion. Those who advanced this criticism overlooked 

 the fact that the gastric juice is manufactured by living cells which are 

 subject to chemical and psychical stimulation and that water is a 

 chemical stimulant. The first experiments showing that water possessed 

 the power to stimulate the flow of gastric juice were apparently made 

 in 1879 (Heidenhain). This observation was later repeatedly confirmed 

 by other investigators (Carlson, Orr, and Brinkman, Foster and Lambert, 

 King and Hanford, Lonnquist, Pavlov, Sanotzky, Sawitsch and Zeliony), 

 all of whom used lower animals as subjects. Pavlov was not impressed 

 with the stimulatory power of water in fact, he found no stimulation 

 whatever in about 50 per cent of his tests where volumes of water ranging 

 from 100 to 150 c.c. were introduced into the stomachs of dogs. He 

 says : 



"It is only a prolonged and widely spread contact of the water with 

 the gastric mucous membrane, which gives a constant and positive result." 



Foster and Lambert also claimed that volumes of water below ! 00 c.c. 

 exerted no appreciable or uniform stimulation in the stomach of the dog. 

 According to these investigators the increase in the flow of gastric juice 



