526 DIGESTION. 



have shown the passage of non-modified protein into the blood and 

 lymph (page 66). Based upon many investigations on this subject 

 we can consider it possible that under certain circumstances, as on flood- 

 ing the intestinal canal with protein, with a greater permeability of the 

 intestinal wall, as in new-born and sucking animals, and with a dimin- 

 ished modification by the gastric juice, a passage of non-modified pro- 

 tein may take place in the blood-vessels, but that under normal con- 

 ditions this is not the case, or at least does not take place to any men- 

 tionable degree. As a rule, the absorption of protein follows a modi- 

 fication of it. In this connection the experiments of ORNI l are of interest 

 which show that the dog's intestine takes up the serum of the dog but 

 not that of the ox or horse. In regard to the previously split proteins 

 the question arises whether the proteins are chiefly absorbed as pro- 

 teoses 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, 2 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 con- 

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

 proteoses 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 pre- 

 vious cleavage into amino-acids. 



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

 that the proteos.es 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 



1 Pfliiger's Arch. 126, 428 (1909). 



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

 Virchow's Arch., 123. 



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

 Pathol. ge"n., 1907; Zunz, MSmoires cour., etc., Acad. Roy. Med., Belg., 20, Fasc. 1. 



