EXACTITUDE ATTAINABLE IN BIOCHEMISTRY 21 



try placed in our hands the necessary implements and knowledge to 

 essay the task. 



Our second field of study, then, consists in an analysis of the chemical 

 phenomena which accompany or underlie the activities of living, undis- 

 turbed, and more or less normally functioning protoplasm, a field which 

 until recently was almost exclusively the preoccupation of the " experi- 

 mental biologist." Inevitably, however, these two phases of chemical 

 inquiry, so closely affiliated, so mutually dependent, are coming to rely 

 more and more intimately upon each other and hence are being welded 

 more and more firmly into one. Experimental biology drawing upon 

 the rich resources of physiological chemistry, is immensely increasing 

 its exactitude and its certainty, while physiological chemistry, on the 

 other hand, is rapidly widening the horizon of its inquiries in response 

 to inspiration drawn from the field of experimental biology. In this 

 work we will recognize no distinction between these fields, but endeavor, 

 in so far as the limitations of our knowledge permit, to interweave them 

 into one coherent representation of the complex tissue of chemical 

 processes which constitutes life and its immediate consequences. 



THE DEGREE OF EXACTITUDE ATTAINABLE IN BIOCHEMISTRY. 



In the so-called "exact sciences," to wit, mechanics and physics, 

 we have, as a rule, the power to isolate more or less completely any 

 phenomenon or group of phenomena which we wish to study, and to 

 guard them from disturbance by the intrusion of accidental variables. 

 For example, it is not a difficult matter to demonstrate that a falling 

 body experiences a constant acceleration, the most serious intrusive 

 variable being the friction of the air, a variable which can now be very 

 readily excluded in a variety of ways. 1 Similarly, in chemistry, it is 

 not a difficult matter to observe the progress and equilibrium of such 

 a reaction, as, for example, the reduction of iron oxide by hydrogen. 

 The chemicals are procurable in pure conditions, only one reaction 

 occurs, and it is a simple matter to exclude other chemicals and to keep 

 the temperature and pressure of the system constant. In organic 

 chemistry much more complex phenomena are encountered. It is 

 the exception rather than the rule to find a reaction which proceeds 

 evenly and without disturbance by side-reactions or secondary decom- 

 positions. To detect regularities and establish "laws" hi such a system 

 is a task the more complex the greater the number of adventitious 

 variables. 



The difficulties which are encountered in studying organic reactions 

 in laboratory glassware are enormously magnified in studying reactions 



1 It must be remembered that the friction of the air, which to us presents no difficulty, 

 was to our ancestors an insuperable obstacle to the measurement of gravity. In exactly 

 the same way insurmountable obstacles which at this day defeat our ends in physiologi- 

 cal or biochemical research will appear of trivial importance to our intellectual heirs. 

 As a rule such obstacles merely imply that we are attacking the problem from the wrong 

 angle. 



