240 DIGESTION AND ASSIMILATION OF THE FOODSTUFFS 



is an even stronger one, for a considerable proportion of the proteoses 

 and peptones arising from the incomplete hydrolysis of proteins are 

 definitely toxic, and the absorption of this type of protein digestion- 

 product would lead to incessant food-intoxication. It is true that 

 peptones may be absorbed from a ligated stomach, and peptones and 

 proteoses resulting from secondary degenerative changes in the intes- 

 tinal epithelium may be absorbed after prolonged ligation of an intes- 

 tinal loop, and may produce severe symptoms of peptone intoxication. 

 These, however, are circumstances not in the least comparable with 

 those attending normal digestion, for a ligated and distended stomach 

 becomes permeable, as we have seen, to carbohydrates which are 

 normally not absorbed until they reach the intestine, so that the 

 permeability of the gastric mucosa is evidently deranged by this proc- 

 ess. The absorption of toxic proteoses from an intestinal loop is 

 attained only after very prolonged ligation, and while this condition 

 may be comparable with that prevailing in severe intestinal stasis, 

 it is certainly not comparable with the normal phenomena of digestion 

 and absorption. 



In certain cases, which must be admitted to be exceptional, individ- 

 uals may display phenomena of Anaphylaxis after the ingestion of 

 particular proteins toward which the individual has an idiosyncrasy. 

 Thus, hyper sensitiveness to the proteins of horse-serum is not unusual 

 and is responsible for the majority of cases of Serum-sickness and deaths 

 arising from the use of Diphtheria Antitoxin prepared from horse-serum. 

 It is especially frequently displayed by chronic asthmatics. A smaller 

 proportion of individuals are hypersensitive to the proteins in the 

 white of egg and betray symptoms of anaphylactic shock, such as 

 Asthma, when they have partaken of eggs. Others, again, are hyper- 

 sensitive to the protein in strawberries, others to the proteins in shell- 

 fish and so forth. In all of these cases we must assume, from the char- 

 acter of the symptoms, that the absorption of a proportion of unaltered, 

 native protein is responsible for the disorder. The proportion of pro- 

 tein absorbed which would suffice to account for these effects, however, 

 is excessively small. Thus Wells has shown that the injection of such 

 a minute amount as one millionth of a gram of crystallized egg-albumin 

 will sensitize a guinea-pig, so that a subsequent intravenous injection 

 of no more than one-tenth of a milligram of the same substance will 

 lead to fatal shock. The comparative rarity of these phenomena of 

 protein-intoxication, and the minute proportion of absorption of 

 unaltered protein which would evidently suffice to evoke them, afford 

 eloquent testimony to the difficulty with which native proteins and 

 peptones are absorbed without preliminary digestion. 



We are thus brought indirectly and by the exclusion of other possi- 

 bilities, to the conclusion that the proteins of the diet must be com- 

 pletely broken down into Amino-acids prior to their absorption. Direct 

 evidence of the correctness of this view has, however, been obtained 

 in recent years in a variety of ways, of which the following are the 

 more important. 



