434 ELEMENTS OF BIOLOGY 



various forms o£ animal life. Applied Science is interested because 

 they reveal or suggest how control may be established. 



The cell doctrine, the nature of protoplasm and of its response to 

 drugs and chemicals and of its defenses against injurious factors in 

 its environment, the nature of immunity, of contractility, of growth, 

 of reproduction, and so on, are first the problems of the academic 

 biologist. Practical applications of his findings are a part of the art 

 of medicine. An illustration of the close interests of the two, but 

 with widely different objectives, may be useful. The theory of anaes- 

 thesia, that is, the reversible decrease in irritability that results from 

 exposure of the living organism to a wide variety of conditions, 

 concerns the abstract biologist. His curiosity is stimulated by the 

 problem of the nature of irritability and of the way in which various 

 environmental conditions affect or extinguish it. The surgeon is 

 interested in finding the perfect anaesthetic, the anaesthetic which 

 will produce profound and sustained insensibility to injury or pain 

 without danger and without injury or after effects. The close rela- 

 tion between these two interests in anaesthesia is so clear that it need 

 not be discussed further. 



It has been pointed out (p. 294) that in abnormal growths such as 

 the various types of malignant and benign cancers or tumors, cells 

 divide; in the benign type they undergo differentiation. The prob- 

 lems of why cells divide and what are the controlling chemical 

 events in cell differentiation constitute most intriguing interests to 

 the pure scientist. To the physician any solution of these problems 

 would immediately suggest methods of control of such adventitious 

 cell divisions as go on in cancerous tissue. 



The Mendelian laws have become tools of great value in the 

 breeding of domesticated plants and animals. Exceedingly impor- 

 tant results have been secured in applying the principles of Genetics 

 to securing disease-resistant and low temperature-resistant strains of 

 plants. Similarly, breeding for high yield factors has increased the 

 economic value of lands. It has been possible to know in advance 



