798 PHYSIOLOGY 



formed. Only 25 per cent, of the starch of "the bread had been rendered soluble, and 

 of this, 21 per cent, was in the form of dextrine and 4 per cent, in the form of sugar. 

 No absorption however either of the digested proteins or of the digested carbohydrates 

 was ever found to take place in the stomach. 



DUODENAL DIGESTION. The influence exerted by the pancreatic juice, bile, 

 and succus entericus, poured out on the food in the duodenum, was studied by analysis of 

 the intestinal contents leaving the intestine by a fistula, either at the lower end of 

 the duodenum, or in the jejunum, or in the ileum. From the duodenal fistula the 

 expulsion of food occurs at repeated intervals, but in a somewhat irregular fashion, 

 its movements being determined partly by the contractions of the stomach and partly 

 by those of the duodenal wall. Usually a large gush is followed by a series of small 

 gushes. Although only a foot intervenes between the duodenal fistula and the pyloric 

 fistula, a great difference is observed in the character of the intestinal contents obtained 

 in the two cases. The outflow from the duodenum, being mixed with the pancreatic 

 juice and the bile, is yellow in colour and increased in amount. With a meal of 200 grm. 

 there is secreted on the average 130 grm. of bile and 140 grm. of pancreatic juice. During 

 its passage through the duodenum the carbohydrates of the food undergo considerable 

 changes, so that even one foot below the pylorus we find that one-half to three-fifths 

 of the carbohydrates have been converted into dextrine and sugar. A further digestion 

 of the proteins also takes place amounting to about one-tenth of the whole protein 

 taken with the food. 



On deducting the amount of juices which have been added to the food, it is found 

 that even in this short length of intestine absorption has taken place of about one-sixth 

 of the ingested food, about one-fourth of the carbohydrates having been absorbed 

 and about one-eighth of the proteins. 



In a dog with a fistula about the middle of its small intestine, the outflow began 

 six to fifteen minutes after the meal, and lasted six or seven hours. The outflow was 

 by small gushes repeated at intervals of five to ten seconds, separated by intervals of 

 one to five minutes, during which nothing appeared at the orifice of the cannula. The 

 material obtained was quite different in character from that flowing from the duodenal 

 fistula. The pasty character had disappeared, the material forming a frothy, orange- 

 yellow, even jelly-like mass with practically no trace of undigested bread. 



From a fistula in the ileum the outflow occurred at long intervals of three to fifteen 

 minutes and was much scantier than that obtained from the jejunal fistula, consist- 

 ing of a thick jelly-like, orange-coloured mass. Both proteins and carbohydrates were 

 entirely digested, and in the case of the former the chief products of digestion consisted 

 of ammo-acids. Thus in one experiment, after four large meals of 500 grm. of meat 

 each had been given in order to obtain sufficient quantity for analysis, 175 grm. of 

 soluble substances were obtained. From this were isolated tyrosine, leucine, alanine, 

 aspartic acid, lysine, and traces of arginine and histidine. 



From a fistula in the caecum there was no outflow until four or five hours after the 

 meal had been taken. The material from the gut was then extruded in faecal-like 

 masses at long intervals of one half to one hour. This regular outflow lasted for about 

 six hours. The reaction of the contents was strongly alkaline, with no food particles, 

 and the material contained merely debris of cells, with small traces of sugar, dextrine 

 and unaltered starch. The absorption of the foodstuffs is thus practically complete 

 by the time that the food has reached the lower end of the small intestine. 



The following Table gives the total amounts obtained in a series of experiments 

 from the different fistulse after administration of 200 grm. of bread, and also the 

 percentage amount of foodstuffs which had been absorbed before the food had arrived* 

 at t he level of the fistula in question : 



Total amouuts obtained Absorbed 

 from 200 grm. of bread per cent. 



Pyloric fistula . . . 691 grm. 



Duodenal fistula . . . <i!l IT tr. 



Jejunal fistula . 585 37-77 



Ileum fistula . 412 (.7-65 



Ciecal fistula 80 , 1)4-34 



