522 THE POPULAR SCIENCE MONTHLY 



All the general laws of life which apply to animals and plants apply 

 also to man. This is no mere logical inference from the doctrine of evo- 

 lution, but a fact which has been established by countless observations 

 and experiments. The essential oneness of all life gives a direct human 

 interest to all living things. If " the proper study of mankind is man," 

 the proper study of man is the lower organisms in which life processes 

 are reduced to their simplest terms, and where alone they may be sub- 

 jected to conditions of rigid experimentation. Upon this fundamental 

 likeness in the life processes of man and other animals is based the won- 

 derful work in experimental medicine, which may be counted among the 

 greatest of all the achievements of science. 



The experimental study of heredity, development and evolution in 

 forms of life below man must certainly increase our knowledge of and 

 our control over these processes in the human race. If human heredity, 

 development and evolution may be controlled to even a slight extent, 

 we may expect that sooner or later the human race will be changed for 

 the better. At least no other scheme of social betterment and race 

 improvement can compare for thoroughness, permanency of effect, and 

 certainty of results, with that which attempts to change the natures of 

 men and to establish in the blood the qualities which are desired. We 

 hear much nowadays about man's control over nature, though in no 

 single instance has man ever changed any law or principle of nature. 

 What man can do is to put himself into such relations to natural phe- 

 nomena that he may profit by them, and all that can be done toward the 

 improvement of the human race is to consciously apply to man those 

 great principles of development and evolution which have been operating 

 unknown to man through all the ages. 



Phenomena of Development 



One of the greatest and most far-reaching themes which has ever 

 occupied the minds of men is the problem of development. Whether it 

 be the development of an animal from an egg, of a race or species from 

 a preexisting one, or of the body, mind and institutions of man, this 

 problem is everywhere much the same in fundamental principles, and 

 knowledge gained in one of these fields must be of value in each of the 

 others. Ontogeny and phylogeny are not wholly distinct phenomena, 

 but are only two aspects of the one general process of organic develop- 

 ment. The evolution of races and of species is sufficiently rare and 

 unfamiliar to attract much attention and serious thought; while the 

 development of an individual is a phenomenon of such universal occur- 

 rence that it is taken as a matter of course by most people — something 

 so evident that it seems to require no explanation ; but familiarity with 

 the fact of development does not remove the mystery which lies back 

 of it, though it may make plain many of the processes concerned. The 

 development of a human being, of a personality, from a germ cell is the 



