PEPTONE. 41 



these substances shows a gradual and progressive falling off 

 of carbon as digestion progresses. But the tables given 

 show another very noticeable feature, and that is that the 

 percentage composition of the individual proteoses differs 

 in the two digestions ; the substance called proto-vitellose, 

 for instance, in the digestion carried on for three days, 

 cannot be the same as that with the same name in the 

 digestion carried on for ten days, although both give the 

 same reactions, specific rotation of the plane of polarised 

 light alone excluded. This cannot be due to analytical 

 errors ; a skilled investigator of Professor Chittenden's 

 eminence could not fall into such a mistake ; besides other 

 proteids, egg-white, for instance, under the influence of 

 superheated steam gives similar results. 



The explanation advanced is that the four substances 

 named merely represent the main steps in the hydration 

 process, but that there are further links in the chain mixed 

 with these, which cannot at present be separated, and which 

 manifest the same general chemical behaviour. 



Such a result is not altogether unexpected ; it only 

 shows how, in spite of the advance Of chemistry as a whole, 

 it is practically at a standstill so far as the proteids are con- 

 cerned ; nor can we hope to understand the steps in pro- 

 teolysis until the chemists are able to give us some idea of 

 the chemical constitution of the proteids which these diges- 

 tive juices act upon. 



One of the properties alluded to, which the proteoses 

 and peptones agree in possessing, is their power of diffusing 

 through membranes ; and although these products of diges- 

 tion do not avail themselves of this to the full, for we never 

 find them in the blood, it can hardly be doubted that the 

 formation of diffusible from indiffusible substances must 

 fulfil some useful end. It appears to be the main object of 

 all digestion, whether of proteids or carbohydrates. It may 

 be held that it enables the substance to be absorbed to start 

 ■on its journey, though in the progress of that journey blood- 

 wards the property in question is lost. 



The same two names are associated with the investiga- 

 tion of this point with accuracy. They worked indepen- 



