38 BORDER LINES OF KNOWLEDGE 



lar and scientific belief, of the existence of a common 

 base of all albuminous substances, the so-called protein^ 

 has not stood the test of rigorous analysis. The divis- 

 ion of food into azotized and non-azotized is no doubt 

 important, but the attempt to show that the first only 

 is plastic or nutritive, while the second is simply calori- 

 faoient^ or heat-producing, fails entirely in the face of 

 the facts revealed by the study of man in different cH- 

 mates, and of numerous experiments in the feeding of 

 animals. I must return to this subject in connection 

 with the respiratory function. 



The sugar-making faculty of the liver is another 

 " catalytic " mystery, as great as the rest of them, and 

 no greater. Liver-tissue brings sugar out of the blood, 

 or out of its own substance ; — why ? 



Quia est in to 

 Virtus saccharitiva. 



Just what becomes of the sugar beyond the fact of its 

 disappearance before it can get into the general circula- 

 tion and sweeten our tempers, it is hard to say. 



The pancreatic fluid makes an emulsion of the fat 

 contained in our food, but just how the fatty particles 

 get into the villi we must leave Briicke and Kolliker to 

 settle if they can. 



No one has shown satisfactorily the process by which 

 the blood-corpuscles are formed out of the lymph-cor- 

 puscles, nor what becomes of them. These two ques- 

 tions are like those famous household puzzles, — Where 

 do the flies come from ? and. Where do the pins go to ? 



