ABSORPTION OF PROTEID S. 44 1 



Neumeister l states that albumoses and peptones dissolved in 

 whipped blood can be changed by mere contact with pieces of living 

 intestine, the rapidity of change being increased when a slow stream of 

 air is driven through the mixture, so as to bring the pieces of intestine 

 into rapid contact with different portions of the blood and albumose. 



Hof meister 2 observed a considerable increase in the number of 

 leucocytes in the intestinal wall during digestion of proteids, and argued 

 from this that these took a considerable share in proteid absorption and 

 in the conversion of albumoses and peptones in the adenoid tissue of 

 the intestinal w r all, and in the mesenteric lymphatics. There is little 

 experimental ground for belief in such a theory. In the first place, 

 proteid is not absorbed to any appreciable extent by the lymphatics ; 

 secondly, albumoses are not changed, as Hofmeister 3 himself has shown, 

 in the blood, which contains plenty of leucocytes ; thirdly, Heidenhain 4 

 has shown that the amount of leucocytes in the wall of the intestine 

 (and the amount of active mitosis in these) is too small to render them 

 adequate for such a purpose. Finally, Shore 5 has shown that, after 

 slow injection of a small amount of peptone (*049 grms.) into a lym- 

 phatic of the hind-limb in a dog, this can be detected again in the course 

 of twenty minutes in the chyle flowing from a fistula of the thoracic 

 duct, showing that it has traversed the lymphatic system unchanged. 



All these experiments go to prove that albumoses and peptones are 

 modified during their passage through the epithelial cells by the action 

 of living protoplasm. What substances are formed from them is not 

 known by direct experiment, but it is highly probable that the process 

 is one of conversion backwards into coagulable proteid. It is known 

 that coagulable proteid can be artificially obtained from peptone and 

 albumose, 6 and that albumose and some forms of peptone used as foods 

 can replace coagulable proteid in maintaining nitrogenous equilibrium. 

 It is difficult to see how such a result can be attained otherwise than by 

 a formation of coagulable proteid from albumose and peptone. 



The percentage of any proteid foodstuff, which is absorbed from the 

 alimentary canal, may be deduced fairly accurately from a comparison 

 of the amount of nitrogen in the food with that of the urine and fasces 

 when such a food is taken into the system. 



Experiment shows that the various forms of proteid are utilised by 

 the organism in widely varying degrees. It does not necessarily follow 

 that a food of which the nitrogenous part is only partially absorbed is 

 on that account to be despised as an adjunct to other classes of 

 nitrogenous food ; vegetable proteid is absorbed much more imperfectly 

 than that from animal sources; but vegetable food, amongst other 

 things, is valuable for the consistency and bulk it gives to the food, 



1<( Lehrbuch der physiol. Chem.," Jena, 1893, Th. 1, S. 251; Ztschr. f. ioL, 

 Miinchen. 1890, Bel. xxvii. S. 324. 



2 Arch. f. exper. Path. u. PharmakoL, 1885, Bd. xix. S. 32; 1886, Bd. xx. S. 291 ; 

 1887, Bd. xxii. S. 306. See also Pohl, ibid., 1888, Bd. xxv. S. 31 ; Heidenhain, Arch. f. 

 d. ges. Physiol., Bonn, 1888, Supp. Heft., Bd. xliii. S. 72. 



3 Hofmeister (loc. cit., Bd. xix.) is of the opinion that the portion of "peptone" which 

 he believes enters the blood unchanged is converted in the tissue, "peptone" being found 

 during digestion in the arteries but not in the veins. The presence of any albumose or 

 peptone, even in the arteries, is, according to more recent observers, however, very doubt- 



4 Loc. cit. 



5 Journ. Physiol., Cambridge and London, 1890, vol. xi. p. 553. 



6 See p. 400. 



