CHOICE OF METHODS 



The selections will depend on several considerations. The first is what one 

 wants to discover. Many investigators in biology and medicine wish to obtain 

 more information about structural components of the body whether gross, micro- 

 scopic or submicroscopic in size. They desire to obtain further data on the 

 physical and chemical properties of these components whether solid or fluid in 

 different physiological stages of activity and in disease in both man and in 

 animals. They are interested in subjects, not personalities, so that in this 

 alphabetically arranged presentation the names of individuals are seldom listed. 

 Emphasis is given to subjects. After all the problems continue while the names 

 of generation after generation of individuals fade out. 



Those who perchance may consult this book will need help at two levels. It 

 may be a simple question of the nature of some dye, or the composition of some 

 solution, or the making of a well known test, or it may be the selection of a 

 technique to be employed in a comprehensive series of experiments. In the 

 latter case it involves a major decision. It is necessary not only to choose the 

 technique most likely to lead to the answer but also give some thought to the 

 equipment required and the training demanded for its proper use. 



A few leading references to the most recent utilization of the technique in 

 question may be helpful. But to discuss the history of its development and to 

 assess priority is not attempted. A complete discussion of the literature may in- 

 deed constitute a handicap by providing an excuse for doing nothing. To be 

 stuffed with information may give a feeling of frustration. 



Some chemical and physical procedures are well within the reach of people 

 who are neither chemists nor physicists while others will simply lead them 

 beyond their depth into futility. It is equally true that well trained chemists 

 and physicists are Ukely to fail to reahze the complexity of vital processes and to 

 make little progress through ignorance of physiology and pathology. Conse- 

 quently one should never hesitate to seek advice from friends in other depart- 

 ments. 



1. To Examine Directly in Vivo 



The ideal arrangement is to look into the body and to study its parts as they 

 function without causing any disturbance. With protozoa and certain small 

 transparent invertebrates this is relatively simple. The web of a frog's foot is 

 thin and can easily be looked through without seriously interfering with the 

 frog. Some other parts of the bodies of various aquatic lower forms lend them- 

 selves to direct examination in vivo ; but there are definite limitations in such a 

 study of what is going on in the human body. It is possible to peer into the 

 various apertures but to get close enough to the living tissues to use high mag- 

 nifications is not feasible. The cornea and lens of the eye are transparent and 



XV 



