ABSORPTION OF PROTEINS. 527 



large quantities in the intestine pass in small amounts into the blood. 

 Another proof is the findings of BoRCHARDT, 1 that after feeding dogs 

 with not too large amounts of elastin, the passage of a proteose, the 

 hemielastose, could be detected in the blood. Attention must also be 

 called to the fact that according to HoFMEiSTER 2 the walls of the 

 stomach and intestine are the only parts of the body in which pro- 

 teoses and peptones occur during digestion. 



We have reason for believing that the proteoses, as well as their 

 cleavage products, are taken up by the intestine, and if this is the case 

 the next question to be answered is, in what form do these bodies leave 

 the intestine and pass into the blood? 



In order to decide this question the blood has been repeatedly 

 tested in regard to the quantity of proteoses. As seen on page 264 

 this has led to very contradictory results, and if we exclude those 

 exceptional cases where a large quantity of proteose was introduced 

 into the intestine at once, then we can say that the occurrence of pro- 

 teoses in the blood, or at least in the blood-plasma, has not been posi- 

 tively shown under physiological conditions. 3 It can also be said that 

 such investigations do not prove much because of the large quantity 

 of blood passing through the intestine for a given time, and the quan- 

 tity of proteose must be so small, so that when divided in the entire blood 

 it can hardly be detected. It is therefore of interest that neither amino- 

 acids nor proteoses were found in the blood after cutting out several 

 organs or groups of organs so that the blood circulated only through 

 the intestinal canal, heart, lungs, pancreas and intercostal muscles 

 (KUTSCHER and SEEMANN, v. KoROSY 4 ). 



We are therefore obliged to consider that the proteoses and amino- 

 acids are transformed in the intestinal walls in some manner or other. 

 Such a belief, especially applied to the proteoses, coincides with the 

 observations of HOFMEISTER, that the proteoses occurring in the mucous 

 membrane during digestion disappear at the temperature of the room 

 from the removed, but still apparently living, mucous membrane after a 

 certain time. This also coincides well with the observations of LUDWIG 

 and SALViOLi. 5 These investigators introduced a peptone solution into 

 a double-ligatured, isolated piece of the small intestine, which was kept 

 alive by passing defibrinated blood through it, and observed that the 



1 In regard to the literature on proteoses in the blood see Chapter V, footnotes 

 1, 2 and 3, p. 264. 



2 Zeitschr f. physiol. Chem., 6, and Arch. f. exp. Path. u. Pharm., 19, 20, 22. 

 8 See footnote 1. 



4 Kutscher and Seemann, Zeitschr. f. physiol. Chem., 34; v. Korosy, ibid., 57. 

 6 Arch. f. (Anat. u.) Physiol., 1880, Supplbd. See also Cathcart and Leathes, 

 Journ. of Physiol., 33. 



