viii PREFACE 



tance of such studies, the writer's interest was drawn 

 to the factors which rendered unfit those that could 

 not survive the rigors of an enforced environment. 



This aspect of experimental biology, which has 

 been neglected by most biologists except in so far as 

 it relates to medicine, has continued to occupy the 

 writer's attention for many years, and the results of 

 numerous experimental researches have been pub- 

 lished from time to time over a period of four decades. 

 Many of these investigations have been recorded in 

 journals not readily accessible to biologists; hence at 

 the instigation of my son, Fenton B. Turck, Jr., I 

 have deemed it advisable to publish the main results 

 of my investigations in monograph form. Such a deci- 

 sion has proved advantageous, as it has permitted a 

 more logical sequence and correlation of related ideas 

 than was possible in the original publications. In- 

 deed, in reviewing some of the older data, we have 

 been able to deduce relationships between what at 

 first appeared to be unrelated facts; and in numerous 

 instances it has been gratifying to find that other in- 

 vestigators have recorded observations which coin- 

 cide nicely with some of our own. 



In a large measure the author's work has been the 

 outgrowth of his initial studies on the cause of shock, 

 and death from this cause. Almost at the beginning 

 of our experiments, the conclusion was reached that 

 shock induced in any manner whatsoever is essentially 

 the expression of the action of a toxic substance liber- 

 ated from injured tissues. Subsequent investigation 

 has completely substantiated this concept, and has 

 shown that the same toxic substance may affect the 

 behavior of animal cells in a variety of ways. We shall 



