DR. PAVY AND DIABETES 25 



rounded. Now, be it noted, it by no means follows that, even 

 in the case of the amoeba, all the digested food material is 

 " assimilated." Assimilation in the strict sense may, in the 

 case of ingested protein, for instance, be a highly selective 

 process even in unicellular organisms and other chemical 

 changes may follow mere hydrolysis in the vacuole. It is 

 clear that interactions may occur in interplasmic spaces less 

 obvious to the microscope than the large but temporary food 

 vacuole of the amoeba ; it has been boldly suggested by 

 Hofmeister, in fact, that a tissue-cell may be a laboratory in 

 which a great number of isolated interactions precede, each 

 in its own locality. The colloid nature of the medium and 

 indiffusibility of specific enzymes secure the localisation and 

 independence of the individual interactions. Such a view 

 may go too far and it cannot be claimed that physiological 

 thought has yet clarified itself in connexion with such matters 

 but it is of importance to recognise there is no necessity to 

 assume that " dead " matter must become " living " matter 

 before it suffers biochemical change. In a case which specially 

 interests us at the moment, that of sugar in its relation to 

 glycogen, there is full justification for the belief that the con- 

 version of either into the other involves no merging into an 

 unknown complex of bioplasm but only the progress in the one 

 direction or the other of a simple reversible interaction con- 

 ditioned by a specific enzyme. That some property of the 

 cell controls the direction of the interaction in a manner that 

 is largely unknown is a fact which must be admitted. 



If we now consider Pavy's later teaching as to the part 

 played by the liver in the metabolism of carbohydrates, we 

 shall meet with an illustration of his more or less unconscious 

 adjustment to modern views. As already stated, he came to 

 think that when the intestinal mechanism is normal the liver 

 plays but a subordinate part in arresting unassimilated sugar. It 

 forms glycogen just as other organs form glycogen from the 

 complexes containing carbohydrate brought to it by the blood. 

 Because of its position and special activities it forms pro- 

 portionately more of this substance than do other organs. 

 When in 1894 he wrote his Physiology of Carbohydrates, 

 he had come to speak of the hepatic glycogen as a " store " of 

 carbohydrate ; but, at this stage, he still appeared to view it as 

 stored by the liver for its own purposes, just as a yeast-cell 



