THE PARENTERAL INTRODUCTION OF PROTEINS 343 



(a) At best the gastric juice forms peptone slowly, and 

 the time during which the food is detained in the stomach 

 does not permit of its complete peptonization. It will be 

 understood that the action of the pancreatic juice was 

 not known, nor had erepsin been discovered when Briicke 

 wrote. (6) In an animal killed while in digestion, Briicke 

 found forty-eight hours after death coagulable protein not 

 only in the chyle vessels in the intestinal walls, but in the 

 intestinal villi, and he concluded that this could come only 

 from the absorption of unaltered protein, (c) Briicke argued 

 that the absorption of unbroken protein is quite as possible 

 as that of fat, since the molecule of the former could not 

 be larger than that of the latter. This argument assumed 

 that the absorption of both proteins and fats is simply a 

 process of filtration. 



Diakonow 1 supported the theory of Briicke because 

 peptone cannot be found in large amount in the blood. 

 Voit and Bauer 2 and Eichhorst 3 concluded that unaltered 

 protein is absorbed because they found that the introduction 

 of protein in the large intestine is followed by increased 

 elimination of urea. This certainly is proof that the protein 

 is absorbed, but not proof that it is absorbed unaltered. 

 Eichhorst showed that a glycerin extract of the mucous 

 membrane of the large intestine had no digestive action, 

 but he did not show that the large intestine did not contain 

 any pancreatic juice and this might have digested the 

 proteins. Fick 4 took an aqueous solution of peptone and 

 precipitated it with alcohol, then dissolved the precipitate 

 in water and injected it into nephrotomized dogs. He found 

 that the blood after this treatment yielded a larger amount 

 of nitrogenous material soluble in alcohol and precipitable 

 with mercuric nitrate, and he concluded that peptone 

 introduced into the blood is speedily converted into urea 

 without being employed in tissue building, while unaltered 



1 Hoppe-Seyler's med. chem. Untersuchungen, 1867. 



2 Zeitsch. f. Biol., 1869, v 



3 Pfliiger's Arch., 1871, iv,570; 4 Ibid., 1872, v, 40. 



