54 SELECTION OF TECHNIQUES 



vacuum tubes for brains, would agree that the most completely mecha- 

 nized work is not necessarily the most "scientific." Some of the definitive 

 solutions to biological problems have been achieved through the use of 

 simple glassware and careful observation. Each investigator must choose 

 for himself between the simple and the elaborate. 



Another choice, not always so obvious, is the choice between a direct 

 observation and an indirect observation. Living cells sometimes resist 

 direct observation by the contemptible trick of dying. Even some biologi- 

 cal chemicals can be observed only indirectly. For example, because most 

 of the ordinary protein molecules are not visible, information about their 

 structure must be obtained by indirect methods. It is possible to measure 

 viscosity, density, mechanical properties, solubility in various solvents, 

 and chemical make-up, but the picture pieced together from these bits 

 of information will never be as complete as if the individual atoms and 

 bonds could be seen. 



y 



Some questions worth asking 



Probably the easiest way of organizing the evaluation of an instrument 

 or technique is to ask a series of questions about it. The following set 

 will illustrate some features that are usually worth considering. 



(1) Purpose. For what purpose was the instrument designed? Is the 

 technique adaptable to the present needs? Under what circumstances 

 should this method be used? Is the instrument likely to be used for a pur- 

 pose more exacting than originally intended? 



(2) Theory. What is the basic principle of the technique? What is 

 really being measured? Which physical or chemical laws are the bases of 

 this technique? Does it measure what we want to measure? 



(3) Details. How is the instrument constructed to accomplish its 

 purpose? What kind of equipment or supplies are required for this 

 method? What does each knob control? Is a schematic diagram of the 

 electrical or electronic system, the mechanical components, or the optical 

 system available? Could the instrument be repaired or adjusted if neces- 

 sary? 



The knowledge of these details increases the pleasure in the experi- 

 ment, and the operator of the instrument becomes most competent when 

 he is familiar with them. Any unusual behavior is quickly noticed and 

 easily diagnosed. More than one graduate student has been embarrassed 

 during the final examination covering his thesis when one of the exam- 

 iners asked what was in the "black box." 



