398 POPULAR SCIENCE MONTHLY 



belief that the quantitative needs of the body for protein food are more 

 satisfactorily met by a liberal addition of vegetable matter with its 

 larger calorific or heat-producing power and smaller nitrogen content. 

 In view, however, of what has been stated concerning the divergent 

 chemical structure of individual proteins, it is obvious that a new 

 standard of comparison is at hand, the suggestions it may offer to be 

 tested by appropriate feeding experiments on man and animals. Truly, 

 no chapter of nutrition is more deserving of careful consideration, 

 both from a scientific standpoint and from its bearing on the welfare 

 of the human race, than that which deals with the relative capabilities 

 of the various proteins of animal and vegetable origin. 



In all that has been said we see emphasized the ability of the living 

 organism to break down its complex food material, as well as the cor- 

 responding material of its tissues and organs, into the simplest of 

 chemical fragments, coupled with the capacity to construct equally 

 complex tissue material out of the fragments so produced. Profound 

 and progressive hydrolysis, rather than simple oxidation, is the method 

 of decomposition, for many of the fragments at least are to be care- 

 fully conserved for future use. Oxygen, however, may play its part 

 in connection with the smaller groups, though even here enzyme inter- 

 mediation may still be found a ruling factor. Enzymes are to be 

 detected on all sides, both inside and outside the cells of the individual 

 tissues and organs, and it is through their agency that the varied proc- 

 esses of life are carried forward. The present realization of the pro- 

 found part played by enzymes in the reactions of the animal body is 

 completely transforming our views of life. The so-called vital activi- 

 ties of living tissue or its component cells are no longer shrouded in 

 that mystery which defies explanation, but we see within our reach 

 tangible means of unraveling the complexities of cellular activity. 

 One by one, the old views of living matter and organic structure are 

 giving place to truly scientific conceptions that admit of logical inter- 

 pretation. It is not long since, when chemists and physiologists alike 

 viewed with enthusiasm, akin to awe, the production of an organic 

 compound by synthesis in the laboratory. I well remember meeting 

 the renowned Wohler, then an old man, in one of my early visits to 

 Gottingen. Yet, Wohler was the first to make an organic substance 

 by synthesis. Up to his time, physiologists all believed that organic 

 substances, whether simple or complex, could be formed only through 

 the agency of a living organism. To-day, however, there is almost no 

 limit to our power of producing organic substances by purely chemical 

 synthesis. In the hands of the chemist, many of the reactions of living 

 matter may be duplicated and we are led to see that the living organism 

 makes use of processes which are merely a counterpart of those we have 

 learned to control in the laboratory. 



