v INTERNAL RESTITUTIVE SECRETIONS 291 



disappears, not by decomposition, but by synthetic regeneration 

 into natural protein by the vital activity of the cells of the 

 mucous membrane. The peptone does not in fact disappear from 

 the mucous membrane if this be plunged not into boiling water, 

 which destroys the enzymes also, but into water at 60, which 

 destroys the vitality of the cells without affecting the enzymes. 

 According to Neumeister (1890) considerable amounts of peptone 

 and proteose can be converted in a short time, when they are 

 mixed with dilute blood and fragments of intestine from a freshly 

 killed animal are thrown in, the blood being then agitated with a 

 gentle current of air, so that every part of it conies into contact 

 with the mucous membrane of the intestine. 



Fano (1881) showed that after injecting peptone and proteoses 

 into the blood they disappeared rapidly, while the specific gravity 

 of the erythrocytes increased, which supports the hypothesis that 

 the erythrocytes are the active agents in regenerating the pep- 

 tones, or some of them at least, the peptone being dehydrated and 

 split up with conversion into globulin, by the potassium salts that 

 predominate in these cells, and by the presence of oxyhaemoglobin. 

 He therefore thinks it probable that the more or less peptonised 

 proteins that penetrate into the blood from the alimentary canal 

 may be partially absorbed and stored up by the erythrocytes, as 

 reserve materials which are subsequently poured into the plasma 

 to compensate for the losses it has sustained. 



Hofnieister (1885), on the other hand, supported the hypothesis 

 that the active agents in the regeneration of proteoses and 

 peptones and in their transport in the blood are represented by the 

 leucocytes of the adenoid tissue of the villous mucous membrane, 

 which accumulate there during digestion, and insinuate themselves 

 through the interstices, and perhaps also into the interior of the 

 columnar epithelial cells. He thus attributes to the leucocytes, 

 in the absorption of peptones from the intestine, a function 

 similar to that which the erythrocytes perform in the absorption 

 and transport of oxygen from the lungs to the tissues. Both 

 Fano's and Hofmeister's hypotheses were, however, subsequently 

 contradicted by various facts ; notably by the experiments of 

 Shore, who saw that a small quantity of peptone (5 cgrms.) injected 

 into a peripheral lymphatic of one of the posterior limbs reappeared 

 in the lymph collected from the thoracic duct in 30 minutes. 

 On the other hand, we know that peptone does not completely 

 disappear when it is added in small quantities to freshly extracted 

 blood or lymph, although the former contains numerous erythro- 

 cytes, the latter numerous leucocytes, which long survive under 

 favourable conditions of temperature. 



There can therefore be no doubt that the synthesis of the 

 proteoses and peptones is effected by the vital activity of the 

 epithelial cells of the mucous membrane. 



