ABSORPTION OF PROTEINS. 503 



with a greater permeability of the intestinal wall, as in new-born and 

 sucking animals, and with a diminished modification by the gastric juice, 

 a passage of non-modified protein may take place in the blood-vessels, but 

 that under normal conditions this is not the case, or at least does not take 

 place to any mentionable degree. As a rule, the absorption of protein 

 follows a modification of it, and the next question is whether the pro- 

 teins are chiefly absorbed as proteoses or peptones or as simpler atomic 

 complexes. 



According to the earlier investigations of LUDWIG and SCHMIDT- 

 MULHEIM as well as those of MUNK and ROSENSTEIN 1 it is generally 

 agreed that the products of protein digestion do not pass into the 

 blood through the lymph vessels, but through the intestinal capillaries. 

 The question of the absorption of these products resolves itself into 

 the form in which they are taken up by the intestine and the form in 

 which they pass into the blood. 



It was mentioned above that proteoses and peptones as well as non- 

 biuret-giving products and amino-acids have been found in the contents 

 of the intestine. The amino-acids occur to a less extent than the pro- 

 teoses and peptones. This may indicate that the amino-acids are more 

 abundantly formed, but also more quickly absorbed, but it may also 

 indicate that the amino-acids are produced to a slight extent only, in 

 the intestinal contents. There is no doubt that the amino-acids can be 

 absorbed as such, but there is still another question, namely, whether the 

 proteoses and peptones are absorbed as such or only after a previous 

 cleavage into amino-acids. 



NOLF and HONORE found, what was later substantiated by ZuNZ, 2 

 that the proteoses and peptones disappear more quickly from the 

 intestine than the non-biuret-giving products. This does not prove 

 that the proteoses are absorbed as such, but rather against such a view. 

 A more direct proof for the absorption of the non-split proteoses lies 

 in the fact, as shown by NOLF, that the proteoses when introduced in 

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

 Another proof is the findings of BoRCHARDT 3 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 4 the walls of the 



1 Schmidt-Miilheim, Arch. f. (Anat. u.) Physiol., 1877; Munk and Rosenstein, 

 Virchow's Arch., 123. 



2 Nolf and Honore, Arch, internal, de Physiol., 1905; Nolf, Journ. de Physiol. et 

 Pathol. gen., 1907; Zunz, Me"moires cour., etc., Acad. Roy. Med., Belg., 20, Fasc. 1. 



3 In regard to the literature on proteoses in the blood see Chapter VI, footnotes 3 

 and 4, p. 255, and 1, p 256. 



f. physiol. Chem., 6, and Arch. f. oxp. Path. u. Pharni., 19, 20, 22. 



