PHYSIOLOGICAL CHEMISTKT. 



LECTURE I. 



INTRODUCTION. 



PHYSIOLOGICAL chemistry forms an important branch of the large 

 field of investigation included under physiology. It has, for one thing, 

 the task of determining the chemical composition of the material from 

 which the separate tissues in the living organism are formed. A knowl- 

 edge of the chemical construction of the different organs gives us the 

 answer to certain questions, and forms the basis for further inquiry. 

 It is perfectly clear that the organism must receive in its nourishment all 

 those elements of which its tissues are composed. With the knowledge of 

 the composition of the separate organs, we obtain, by comparing their 

 functions, certain interesting views regarding the significance of the dif- 

 ferent substances which take part in their formation. Closely related to 

 such problems stands the investigation of metabolism. This has become 

 almost exclusively the domain of the physiological chemist. We desire, 

 first of all, to know as much as possible concerning the nutriment that the 

 organism receives, and especially as regards its utilization in metabolism. 

 We obtain an insight into such processes by carefully studying the excre- 

 tions from the organism. The physiological chemist has long since passed 

 beyond these boundaries. His foremost task is now to ascertain what 

 becomes of each separate group of food-stuffs in the organism, in what 

 way it reaches the tissues, and how the cells utilize the different substances 

 in their metabolism and are built up by them. For a long time we have 

 not been content with merely contrasting the income with the outgo of 

 the organism. A final goal of physiological-chemical research will be 

 attained, when we are able to follow, in every separate phase, each and 

 every food-stuff from the time of its introduction into the alimentary 

 canal throughout its entire stay in the tissues until it is finally eliminated; 

 so that a whole chain, without any missing links, of all the different trans- 

 formations and complicated processes will lie exposed to our view. We 

 are still very far from the solution of this problem. To be sure, in recent 

 years certain progress has been made in our knowledge of metabolism, and 

 indeed here and there the advance of pure chemistry has placed certain 



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