20 F R E D M. U B E R 



length of the hfe cycle, relative treetlom from infection, and favorable 

 development and behavior in captivity. 



Other factors being equal, the most favorable organism from the 

 standpoint of the particular type of experimentation should be 

 selected. Since other things are usually not equal, the occasion is 

 rare when the choice of an experimental organism should be based 

 solely on its favorable characteristics or response for one specialized 

 type of investigation. Some of the decisive contributory factors will 

 be discussed in succeeding paragraphs. 



2. Select a Widely Used Organism 



Of the large amount of biological experimentation, probably more 

 than 99% is done on less than 1% of the known species of organisms. 

 Quantitative studies, whose significance depends largely on the 

 critical use of special physical methods, are conducted usually on a 

 few standard biological materials. Most genetic studies involving 

 physical agents for the production of mutations, for example, are made 

 on Drosophila melanogasier and on Zea mays. Nutritional studies are 

 confined largely to white rats, although use is made also of white mice, 

 rabbits, guinea pigs, and other domestic animals. Monkeys and 

 dogs are less frequently objects of study, but are important in that 

 their response often closely parallels that of man. A list of the bio- 

 logical materials most commonly employed for quantitative investiga- 

 tions of various types would be surprisingly brief. 



In initial or exploratory studies of some supposedly new phenom- 

 enon, it may be thought that the choice of biological material is 

 relatively immaterial as far as the outcome of the experiment is con- 

 cerned. In that event, it would seem most logical to select a very 

 widely used organism. The latter course probably would be advisable 

 even if some slight experimental disadvantage were incurred. As a 

 consequence, the information obtained can be readily evaluated by 

 any one of a large group of experimenters, enabling them to make 

 direct comparisons with other reactions of the same organisms. This 

 course also favors the wider dissemination of the results of research by 

 increasing the potential audience to include those working with the 

 same organism on other problems even though not closely related in 

 nature. The increased value which attaches to an experiment owing 

 to such intercomparisons will probably exceed any apparent tem- 

 porary advantage that would be gained by the casual employment of a 

 relatively unknown genus or species of organism. As an example. 



