56 SELECTION OF TECHNIQUES 



encounter this situation at times, however, and quite frequently he needs 

 to modify a commercial instrument. 



The "design" of any object, as the term is used here, refers to the 

 complete operation of planning and drawing specifications. A properly 

 designed instrument should give desirable answers to all the pertinent 

 questions in the previous section. The design covers the purpose and 

 theory; the materials to be used; the arrangement of the controls, meters, 

 and mechanical parts; details of construction, including tolerances; and 

 even the shape and color of the outer covering. A well-designed instru- 

 ment performs the task for which it was built with accuracy, precision, 

 and convenience. The instrument is "functionally designed" and has no 

 "ruffles." 



The design stage of instrument building might take a very long time 

 and, if well done, often results in a superior instrument. Many home- 

 made instruments, however, are needed immediately, so that six months 

 or a year of designing would seem too long. Would it be better to build 

 a "haywire" gadget that might work? Perhaps, but one must expect diffi- 

 culties if theory and design are only surmised. As an example, a biologist 

 once needed a small blower to provide a stream of air in an experimental 

 chamber. He could find no commercial blower or pump with the proper 

 qualifications, so he made a few rough sketches and started gathering 

 materials to build a blower. Before actually starting construction, how- 

 ever, he thought it would be wise to look briefly into blower design. He 

 found that the blower he had in mind would provide the air stream he 

 needed, but only if it could turn almost a million revolutions per minute. 

 In this case it was easier to redesign the whole experimental arrange- 

 ment. 



The question of whether to spend the effort required to build instru- 

 ments is a serious one. Some biologists throw together the most out- 

 rageous assemblages of miscellaneous parts and produce equipment that 

 performs beautifully. One biologist I know has achieved a reputation for 

 building complicated devices that never work. Only experience and a cer- 

 tain natural knack enable one to decide whether to proceed to the con- 

 struction stage. 



The actual construction may be done by the biologist himself or by 

 a machinist, glass blower, or some other expert. Some biologists enjoy 

 doing their own work and gain the advantage of being able to modify 

 the design as the work is in progress. It is desirable for the experimental 

 biologist to know something about machine shop procedures, sheet metal 

 work, carpentry, electronics, glass blowing, and assorted other special- 



