18 SCIENCE PROGRESS 



further postulates that since sugar is transported from the liver 

 to the muscles and other tissues, where its oxidation takes 

 place, arterial blood should contain more sugar than venous. 

 Pavy's estimations failed to show such excess. 



But if the liver contain no more sugar than other organs and 

 yield no sugar to the blood leaving it, if there be no transport 

 of sugar as such to the tissues, the glycogenic explanation fails. 

 Pavy felt that his researches proved all these negations and, 

 as I have said, disbelieved profoundly in Bernard's views to the 

 end of his life. His disbelief was supported by an argument 

 which for him was conclusive. Normal blood throughout the 

 body contains always a certain small proportion of sugar 

 (about one part in a thousand) and normal urine also contains 

 a definite though small amount. These circumstances have 

 been amply demonstrated by many observers but Pavy himself 

 took much trouble to obtain accurate quantitative data, both 

 from blood and urine. Now, in his view, any variation in the 

 amount of sugar in the former must be promptly indicated by 

 a corresponding variation in that of the latter. He held it was 

 impossible that a diffusible substance, such as sugar, with its 

 relatively small molecules, could fail to pass the kidney in 

 proportion to its concentration in the blood. But as he pointed 

 out, no such variations can be detected in the case of the healthy 

 person. At no time after a meal of carbohydrate is the condition 

 of the urine such as to indicate an increased excretion of sugar ; 

 therefore the constituents of that meal can never enter into 

 general circulation in the form of sugar. 



In his criticism on the experimental work which was sup- 

 posed to support the glycogenic hypothesis by demonstrating 

 a special distribution of sugar in the circulation, Pavy was upon 

 strong ground. His own researches, even the earlier, were 

 made with the aid of better methods and in a more critical 

 spirit than those of his predecessors. If a belief that the 

 liver operates as a storehouse of available carbohydrates must 

 be based on the proof that on occasion sugar passes from it 

 into the blood, in such quantity that it may be detected 

 analytically, Pavy's work deprived that belief of foundation. 

 Those who still hold it are content to point out that the flow 

 of blood from liver to tissues is so rapid that the transport of 

 large quantities of sugar need cause but an infinitesimal per- 

 centage increase in the sample drawn off by the experimentalist 



