igi2] Chemical Interpretation of Vital Phenomena. 271 



between fats and carbohydrates was that the former contain more than 

 twice as much energy as the same weight of the latter. 



Another and entirely different train of thought has been prominent 

 in the history of physiology. Fats and carbohydrates have laid bare the 

 secrets of their constitution; the atoms that compose them are not only 

 present in different proportions but in different groupings which confer 

 upon them different chemical characters. They behave differently, 

 and the relation of chemical structure to physiological function is the 

 problem that has engaged the attention of perhaps the largest number of 

 physiologists in the last generation or two. For these the appreciation 

 of chemical character and subtle differences in constitution is the guiding 

 light. 



The impulse to this study, which is obviously but one part of the 

 great activity of organic chemistry in the last century, is commonly dated 

 from the discovery of Wohler, more than eighty years ago, that urea, 

 the principal nitrogenous substance of those which are produced in the 

 life of the higher animals and man, could be synthesized in the laboratory. 

 We have in our days become so familiar with the synthetic achievements 

 of organic chemistry that it is difficult for our generation to realize how 

 the synthesis of so comparatively simple a substance as urea could come 

 to be a landmark in the history of physiology. We are apt nowadays 

 to be a little impatient that the chemists cannot yet synthesize proteins 

 for us; it is high time with eggs at 75 cents a dozen that synthetic 

 eggs should be upon the market. What are the chemists about? They 

 make hosts of unfamiliar substances the only interest of which, for any 

 but chemists, consists in their unintelligible, labyrinthine complexity. 

 But in the thirties of the last century this was not so. Life was life, 

 and all that came from living things shared in its mystery. There was 

 in those days something uncanny, almost sacrilegious, in the idea that 

 anything produced by living organisms should be capable of being pro- 

 duced by the hand of man. It was as if the wild dreams and fancies of 

 the alchemists should become an actuality. 



This impulse has been strong right down to the present time. It 

 has actuated the work which is associated first and foremost at the present 

 time with the name of Emil Fischer, who has given to Biochemistry 

 more that is solid and substantial than probably anyone that has given 

 anything. It is only with the more exact knowledge as to the consti- 

 tution of sugars and the complex substances built up out of them, with 

 the concrete conceptions that we have begun to have as to the structure 

 of proteins and of the essential groups associated with them in the 

 nucleus of all cells, so much of which is due to him, that the imagination 

 can begin to move with any freedom among the chemical problems of 



