290 PHYSIOLOGY CHAP. 



arterial blood - pressure, with ecchymosis of various organs 

 (Schmidt - MiUheim, Fano, Kiihne and Pollitzer, Neumeister, 

 Shore, Salkowski). It is therefore necessary that the proteoses 

 and peptone absorbed from the intestine shall, before they 

 penetrate into the blood and lymph, be modified until they lose 

 all toxic action. 



(c) The organ which effects this transformation or regeneration 

 is not the liver, as was formerly supposed, because the portal blood 

 contains no more peptone than the rest of the blood. Moreover, 

 if blood containing peptone be circulated through the vessels of 

 the surviving liver, freshly excised from the animal, the peptone 

 does not disappear nor even sensibly diminish in the circulating 

 blood. The same result is obtained if peptone be injected into a 

 mesenteric vein, i.e. in the direction of the liver, in a living 

 animal, the blood of the hepatic vein being then examined 

 (Neumeister). The same appears, again, on injecting peptonised 

 blood by the splenic artery, so that it must pass through the 

 spleen and the liver in succession (Shore). This last experiment 

 shows that the spleen is also incapable of converting peptone into 

 natural protein. 



(d) It was G. Salvioli (1880) who first, in Ludwig's laboratory, 

 demonstrated that proteoses and peptone are synthetised into 

 natural protein in passing through the intestinal walls. He 

 isolated a loop of intestine from a recently killed dog, closed the 

 ends by ligatures, and introduced a gramme of dissolved peptone. 

 Artificial circulation was then established through the arterial 

 and venous vessels of the loop, by which perfect vitality was 

 maintained, as shown plainly by the peristaltic movements. 

 After four hours' circulation in a glass chamber warmed to 37- 

 40 C., he found only about half a gramme of coagulable protein, 

 and hardly a trace of peptone in the intestine. No peptone was 

 found in the circulating blood. If it had been added previous to 

 circulation it was found present in the same amount at the close 

 of the experiment. Evidently, therefore, the peptone absorbed 

 from inside the loop disappeared while traversing the intestinal 

 wall,- before it could reach the blood. Under the conditions of 

 this experiment, however, a part of the peptone is decomposed 

 into amino-acid previous to absorption. 



(0) Hofmeister (1885) showed that the mucous membrane of 

 the stomach and intestine is the sole tissue (except the spleen) in 

 which the presence of peptone can be detected during digestion. 

 But the peptone present in the gastro-intestinal mucous membrane 

 rapidly undergoes conversion. If two equal parts of stomach or 

 intestine are taken from a dog killed during digestion, the first 

 part being thrown into boiling water, the second kept for some 

 time at 40 C. before immersing it, peptone will be found in the 

 former, while there is none left in the latter. In this the peptone 



