FOODS HUMAN NUTRITION. 863 



"Trypsin in the gastric contents is highly resistant to the action of acid 

 and pepsin. In general, tryptic value is high in the presence of low acidity 

 and in alkaline reaction, and of low value when the gastric contents are of high 

 acid concentration. A fall in the acidity is usually accompanied by a rise in 

 the tryptic values, 



" The color of the gastric contents often changes during the period of experi- 

 ment from that of the ingested material to a golden yellow or a dark olive or 

 blue green. This color change is due to regurgitation of bile from the duodenum 

 and is absent on a diet of substances which do not cause the outpouring of bile. 

 The tryptic values in the gastric contents usually rise concomitantly with the 

 color change, although in a non-bile stimulating diet the tryptic value seems 

 independent of the color. 



" Sodium bicarbonate in 5 per cent solution is lield in the stomach until 

 sufficient hydrochloric acid is secreted to bring the alkalinity to a point where 

 it is uonirritating to the duodenum. The retention is accompanied by a high 

 trypsin value — suggesting antiperistalsis in the duodenum in response to an 

 irritant. Sodium bicarbonate in 1 per cent solution hastens the emptying of 

 the stomach either by increasing the motility of the stomach or opening the 

 pylorus. Sodium bicarbonate solutions do not inhibit human gastric secretion, 

 but seem to have a direct stimulatory effect in some cases. 



" Free hydrochloric acid seems unnecessary for the opening of the pylorus, 

 for the stomach sometimes empties while its contents are still alkaline. Five- 

 tenths per cent of hydrochloric acid ingestion is followed by a rapid fall in 

 acidity to about 0.2 per cent, due to a regurgitation of alkaline duodenal con- 

 tents, as is indicated by the rise in tryptic values coincident with the fall of 

 acidity. The acid is then emptied from the stomach. 



" Regurgitation of duodenal contents into the stomach is but another of the 

 protective functions of which the body furnishes so many examples and has for 

 its purpose the defense of the small intestines from irritants." 



An extended bibliography is appended. 



For earlier work in this series see a previous note (E. S. R., 34, p. 659). 



Green color in mother's milk after the ingestion of liver, E. Feer {Biochem. 

 Ztschr., 72 (1916), No. 5-6, p. 378). — In the case of wet nurses it was observed 

 that the milk secreted a few hours after the ingestion of beef or calves' liver 

 had a green color, which was noticeable on comparing it with normal milk. 

 The condition persisted for about 16 hours. The suggestion is offered that the 

 color is due to the presence of some derivative of the coloring matter present 

 in the liver eaten. 



Fasting studies. — XIV, The elimination of urinary indican during two 

 fasts of over 100 days each, C. P. Shebwin and P. B. Hawk {Biochem. BuL, 3 

 (1914), ^^o. 11-12, pp. ■/tl6-419). — In connection with previous studies of this 

 series (E. S. R., 30, p. 765) two fasting experiments with a dog are reported. 

 The fasting periods were 117 and 105 days in length, differing only in the fact 

 that the 105-day fast was a " repeated " one. 



During the initial fast of 117 days the indican output was continuous and 

 fairly high throughout, while during the repeated fast of 105 days the indican 

 values were much lower. On the basis of these observations, the authors con- 

 clude that " the finding of diminished intestinal putrefaction as a result of 

 ' repeated ' fasting is in line with other observations . . . which have shown 

 that ' repeated fasting ' is accompanied by greater resistance, a less rapid los.s 

 in body weight, less pronounced protein catabolism, and a general physical and 

 mental improvement." 



