82 A CENTURY OF PROGRESS IN THE NATURAL SCIENCES 



Natural history, as has been pointed out, made some great contributions to 

 philosophy. Ecology has made, and above all has the potentiality for making, 

 some great practical contributions. There are two aspects in which this last is 

 clearly apparent. One of these is connected with the conservation of renewable 

 resources. The other aspect concerns the application of ecology to medicine. 



We are confronted at the present time with a growing realization that our 

 renewable resources need to be studied. Our forests are beginning to show signs 

 of wear from use. Our wild food animals from sardines to ducks and trout — if 

 we may by courtesy include the last two as ''food animals"^ — are showing signs 

 of depletion. Our soil is suffering from improper handling, which, at least at 

 times, implies improper treatment of the natural covering of grass and woodland. 

 Any solution of these problems depends in the first instance upon a basic knowl- 

 edge of the plants and animals involved, how they maintain themselves, how 

 they reproduce, their requirements, how they fit into an environment that can 

 maintain a balance between their numbers, the food supply that they themselves 

 must have and the food supply that they may yield. 



It is only within recent years that any appreciation of the idea that these 

 problems are fundamentally problems in ecology has begun to develop even among 

 biologists. This is because they have very commonly been approached from some 

 other point of view, such as that of the commercial fisherman, the lumberman or 

 the farmer desirous only of obtaining an immediate return from his activities. 

 But the idea that any proper approach to such problems must rest upon a knowl- 

 edge of the organisms involved is beginning to grow and eventually must become 

 dominant if these problems are to be solved in any satisfactory way. In this lies 

 one of the greatest contributions to human welfare that are still to be made by 

 any subdivision of biology. 



In the relation of ecology to medicine we have a very special situation. A 

 physician is of course primarily concerned with what goes on in the human body 

 and the relation of the doctor's activities to ecology is in many instances more 

 or less remote. It is in connection with diseases of parasitic origin or diseases 

 for which transmission is dependent upon other organisms that his activities 

 come into contact with ecology. Now it so happens that the physician was at 

 one time solely responsible for the development of our laiowledge concerning 

 these diseases. He was concerned with the effects of such diseases as malaria 

 upon the human body, and it was entirely natural, in fact, inescapable, that he 

 should search for the pathogen and explore the problem of how that pathogen 

 gets into the human body. But, since he was the first to inquire into these ques- 

 tions, he quite naturally took over first of all a consideration also of the organ- 

 isms which act as vectors for these diseases. Since it is hardly compatible with 

 human nature to let go a hold that has once been established, the physician con- 

 tinued for some time to include these vectors within the range of his special 

 domain, although he was scarcely qualified by his training to maintain this hold. 

 In fact, the problem of the relation of these vectors to the pathogen and to man 

 is not a medical problem at all except as medical men may be interested in pre- 

 ventive medicine. If I may employ an analogy, consider the instance of injuries 

 from automobile wrecks. The doctor has to treat these injuries and he may be- 

 come impressed, in the course of his duties, by the need for some procedure whicli 

 will reduce the incidence of wrecks. But the prol)lems involved in handlino 



