in DIGESTION IN THE MOUTH AND STOMACH 179 



the niouth, and undergoes few changes in the stomach from the 

 action of the gastric juice, which is confined to starting peptonisa- 

 tion in the gluten. 



The duration of gastric digestion, i.e. the evacuation by the 

 stomach of the food, varies with the quantity and quality of the 

 latter, according to the individual and to the more or less normal 

 state of the digestive organs. Busch stated that after a copious 

 meal, the flow from the upper end of the fistula in the woman 

 above referred to commenced about half an hour after the meal, 

 and almost or entirely ceased after 3-4 hours. 



Many of the sclero-proteins are refractory to the digestive action 

 of gastric juice : e.g. elastin, chitin, fibroin, chondrin. The nucleins, 

 too, are entirely exempt from the action of gastric juice, a fact 

 utilised by Miescher in separating them. Lastly, mucin and the 

 amyloid substances are also very resistant to the action of enzymes 

 in general. 



The digestibility of the various foods or viands, i.e. the time 

 required for their digestion and absorption, can only be determined 

 in the stomach by the very relative criterion of their longer or 

 shorter retention there. The tables drawn up from the observa- 

 tions of Beaumont upon the famous Canadian, St. Martin, and his 

 gastric fistula, have therefore little value. The same may be said 

 of similar researches more recently made by other workers. Those 

 of Fermi, however, have a certain value, particularly from the 

 hygienic standpoint. 



It is more important to form an approximate notion of the 

 time that the foods which consist mainly of the proteins that can 

 be digested by gastric juice remain in the stomach. In a dog 

 with a gastric fistula, 100 grms. of boiled egg-white enclosed in a 

 muslin bag are digested and disappear after 5 hours; 200 grms. 

 of boiled and minced meat were not completely digested in the 

 dog's stomach for over 12 hours (Schmidt - Miihlheim) ; 500 

 grms. raw minced meat were not all digested after 12 hours 

 (Barbera). All these facts confirm the statement that the task 

 of the stomach is confined to merely initiating the digestion of 

 proteins. 



One very important function of the gastric juice is certainly 

 that of sterilising the food and drink ingested, by killing the 

 germs of putrefaction and innumerable pathogenic microbes, and 

 destroying and rendering innocuous the toxines and ptomaines 

 which are formed as the products of their metabolism, or from the 

 putrid corruption of the tissues. This sterilising and antiseptic 

 action, which constitutes one of the great defences of the organism 

 to many morbigenic causes, results from the incapacity of the 

 gastric juice to putrefy, and its antiseptic properties, discovered 

 by Spallanzani (1780). He proved in a series of ingenious ex- 

 periments, which Bunge justly praises as a model owing to the 



