NATURE AND SCOPE OF THE SUBJECT 19 



The investigator of Nature cannot afford to hamper himself by 

 arbitrary definitions and delimitations of his field. When the need 

 arises he must be prepared to use the tools which the problem calls 

 for, be they the tools of physics, chemistry, mathematics, anatomy, 

 bacteriology or pathology. The teacher is somewhat more con- 

 strained. He cannot carry his pupils too far from the center of the 

 subject in hand, lest their lack of preparation should render them 

 unable to follow him. Even so, however, the student of biochemistry 

 will often have occasion to dwell, in his studies, upon certain aspects of 

 problems which the physiologist has made peculiarly his own, and the 

 medical student will frequently find himself studying one and the same 

 problem in his course in biochemistry and again in his course in 

 physiology. Nevertheless he will find that he is not merely repeating 

 his work, not merely covering old ground, but that, on the contrary, the 

 physiologist and the biochemist have each of them something different 

 to say; displaying the problem in different lights and dwelling upon it 

 in different connections. 



We have stated that the science of biochemistry consists in the 

 interpretation of life-phenomena in the light of the facts and principles 

 of chemistry. The question may here very naturally arise in the mind 

 of the reader, How can it be possible to apply chemistry to the investi- 

 gation of living matter? True, we can attempt to analyze living mat- 

 ter, to separate chemical constituents from it and to identify them. 

 But then, directly we begin to analyze living matter it ceases to be 

 living matter. The reagents which we employ immediately "kill" 

 it, that is to say, abruptly suspend its characteristic functions and 

 disperse and dissolve the minute structures of protoplasm which are the 

 physical substratum upon which its functional activities are reared. 

 Unquestionably, an amoeba which has been boiled in hydrochloric 

 acid may yield interesting products, but then it is no longer an amoeba, 

 and the products which analysis yields bear only a remote relationship 

 to those which were originally present in the living organism. 



To find out what is actually occurring in living matter- we must, 

 therefore, employ methods of investigation somewhat analogous to 

 those which the physical chemist employs in the investigation of what 

 is actually occurring in flames. First, we study the nature of the 

 substances which enter the flame, then we study the properties and 

 behavior of the flame itself, always taking care to do so by the aid of 

 instruments which do not disturb the flame, and finally we ascertain 

 what substances the flame gives off. From these various and frag- 

 mentary data we endeavor to reconstruct in our minds a coherent 

 picture of the train of events as they actually occur, and this endeavor 

 will be the more successful in proportion to the extent, the variety and 

 exactitude of our measurements. 



So far as possible, then, we must bring static and not dynamic methods 

 of mensuration to. the study of living matter, methods, that is, which do 

 not involve the cessation of the very processes which we desire to 



