316 SCIENCE PROGRESS. 



more than one worker has already demonstrated the inac- 

 curacies of his experimental premisses. Neumeister (7), 

 for instance, puts the case as follows : — 



First, he shows that the liver cannot make sugar from 

 peptone, as no peptone ever reaches the liver under normal 

 circumstances ; it is reconverted into albumin during its 

 passage through the intestinal epithelium. Feeding experi- 

 ments with peptone do not therefore prove anything. 



Secondly, injection of peptone into the portal vein is 

 also fallacious ; the injection of this toxic material leads to 

 such grave changes in the circulation that any increase of 

 sugar discharged from the liver would more probably be 

 derived from the increased decomposition of glycogen than 

 from the substance injected. 



Thirdly, Seegen finds that pieces of liver removed from 

 the body and digested with blood and peptone yield more 

 sugar than other pieces of the same liver which are not so 

 treated. Neumeister points out that the method used for the 

 estimation of sugar under those circumstances is fallacious ; 

 the sugar was estimated by Fehling's solution in the pre- 

 sence of the peptone ; some of the copper would be taken 

 up in causing the biuret reaction with peptone, so that the 

 remainder would only require comparatively little sugar to 

 reduce it, and if this factor was neglected one would con- 

 clude erroneously, as Seegen did, that the percentage of 

 sugar had risen in the fluid investigated. In the liver of a 

 fasting animal containing no glycogen digestion with pep- 

 tone and blood causes no appearance of sugar. 



Bial's own experiments may be briefly summarised as 

 follows : — 



1. Digestion of liver with blood leads to a oreater forma- 

 tion of sugar than digestion of liver with salt solution. 

 This is due to the fact that blood contains a diastatic 

 ferment (8). 



2. Peptone, like saliva or malt extract, favours the 

 activity of this ferment on solutions of glycogen or starch 

 paste, but leads to the formation of no more sugar from 

 pieces of liver than in those specimens to which blood alone 

 had been added. 



