28 PRINCIPLES OF BIOCHEMISTRY 



Part II. The manner in which the properties of the foodstuffs 

 mould and determine the properties of living protoplasm. 



Part III. In proceeding to consider the activities, apart from the 

 merely passive properties of living matter, we are at once confronted 

 with the significant fact that the multicellular organisms, like our- 

 selves, are really immense societies composed of innumerable minute 

 units which are the individual living cells. We have, in this society, 

 a governing authority, the central nervous system; a postal-telegraphic 

 system, the peripheral nervous system; a laboring class, the muscles 

 and glandular tissue-cells; distributing agencies, the blood and lymph, 

 and with all of these not a rigid central autocratic control, but a very 

 considerable degree of local autonomy. Every cell is working, not by 

 deliberate instruction, but as a part of its very specialized life. In 

 order to avoid confusion in so vast a complex of semi-independent 

 units, numerous cooperative mechanisms must be present to adjust 

 supply to demand and effort to need. These mechanisms imply a 

 certain correlation of distant .parts; for instance, between the neuro- 

 muscular system which controls the respiratory movements, and the 

 need of the tissues for oxygen. This correlation of different and often 

 widely separated activities is brought about by the interaction of two 

 distinct types of agency, nervous agencies and chemical agencies. In 

 so far as this correlation of activities is brought about by chemical 

 means, it will fall under consideration in this third phase of our subject. 



Part IV. In this part we will endeavor to attack the very kernel of 

 our problem, that part of our studies which is destined to provide the 

 ultimate foundation of the practice of medicine and in no small measure 

 of agriculture also. The chemical phenomena which underlie, accom- 

 pany or even actually constitute the living activities of cells will here 

 be our preoccupation and we will incidentally study, so far as our 

 fragmentary knowledge at this time permits, the changes which the 

 foodstuffs or constituents of protoplasm undergo at the instant of their 

 utilization for the furtherance of vital functions. Here we will find 

 our most alluring problems and our least extensive knowledge, here is 

 the region in which must occur the greatest conquests which lie before 

 us and those which will exercise the most fundamental and far-reaching 

 effect upon our own lives and the lives of those who will follow after us. 



Part V. In this part we will take up the study of the waste-products 

 which ultimately result from the activities of oiir tissues; the ashes, the 

 products of combustion and the debris which result from the daily 

 maintenance and furtherance of life. 



Part VI. In this part, regarding the entire body as a chemical 

 machine, somewhat crudely comparable to a steam-engine, we will 

 discuss the question of the efficiency of the machine and the relation- 

 ship of the horse-power it can develop to the nature and value of the 

 fuel with which it is provided. It is in this connection that we will 

 discuss data which may enable us in some measure to answer the 

 question, what investment of particular types and mixtures of fuel will 



