HEREDITY AND EUGENICS. 275 
deeper scientific knowledge being such as to show man more 
clearly than he ever knew before where he can himself come in 
to control its operation in favour of his own desires. 
Passing from plant and animal to the sphere of human life, 
for man’s bodily organism the claim is, of course, made that 
it falls within nature, and that the teaching of biology applies 
to it in every respect. We, too, owe the form of our bodily 
frames to operations which work by heredity according to the 
germ-plasm process, and according to Mendelian law. This is 
so, a priori, for all the reasons which lead us to consider that the 
human body is of the same order as other living organisms. 
Of course this should be verified by inductive process, and there 
are many workers in the field of human anatomy and human 
physiology endeavouring to find evidence for these great laws. 
As to the Mendelic theory, I understand that not much verification 
has yet been secured ; it seems illustrated in the iris, in certain 
diseases of the eye, and in some physical deformities ; and not 
much farther, at present. But we must remember that there are 
special difficulties in the way of studying the biology of man ; 
the successive individuals are so far removed that a century 
gives, normally, only three generations, which compared with 
the rapid production of successive generations of plants, where 
Mendelism has been most abundantly exemplitied, is almost 
prohibitive of success: experiments are out of the question ; 
and material adapted for observation is difficult to secure; but 
the study is only just commenced, and we shall learn more. 
At the same time I think we must here put in a caveat 
against the complete identification of the biology of man with 
that of animals and plants. Man’s body is the seat of a mind, 
and some of the changes which it undergoes are due in the 
first instance to changes which take place in the mental sphere. 
For example, while cancer is often caused by purely physical 
irritations, a specialist assures us that “ by far the most common 
cause” is mental ; “ depression, emotion, trouble, worry, anxiety,” 
are the chief factors in cases which amount to the great 
majority. (Dr. Snow of the Brompton Cancer Hospital, Lecture 
at Birmingham, October 18th, 1908.) ‘The general influence 
ef mind upon body is too far-reaching to be ignored. 
But in the main we may acquiesce in the assignment of the 
human body to the sphere of biological law, and for our present 
study, to the influence of heredity as above indicated. From the 
religious point of view I see no ground for our shrinking from 
this. As soon as we have recognized that man’s physical frame 
is not a special creation but a marvellous instance of the laws 
