504 DIGESTION. 



stomach and intestine are the only parts of the body in which proteoses 

 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 pages 255 and 256 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 proteoses in the blood, 

 or at least in the blood plasma, has not been positively shown under 

 physiological conditions. 1 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 quantity 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. KdROSY). 2 



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. 3 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 

 peptone disappeared from the intestine, but that the blood passing 

 through did not contain any peptone. 



What becomes of the amino-acids in the intestinal wall? KUTSCHER 

 and SEEMANN have shown that the crystalline cleavage products are 

 so transformed in the intestinal wall that they cannot be detected. 

 We have here to think of two possibilities: The amino-acids are either 

 further split or they are used in synthesis (of proteins?) 



It is a long-known fact that with the digestion and absorption an 



1 See foot-note 3, p. 503. 



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



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

 Journ. of Physiol., 33. 



