346 THE PRINCIPLES OF HEREDITY 



capacity to remember experiences and a corresponding 

 capacity to learn how to utilize remembered experiences. 

 Correlated to these mental powers is a large brain. Apart 

 from pathological conditions, therefore, an infant who is born 

 with a large head is, other things equal, better fitted for its 

 start in life than one with a smaller head. The skeleton of 

 the human mother has been so modified that, relatively to 

 her size, she has a much more capacious pelvis than any 

 other mammal. Apart from parturition, however, this 

 peculiarity of shape is a disadvantage. Her feet being close 

 to the median line while her thigh-bones are set wide apart, 

 she is forced to preserve her balance, when walking, by sway- 

 ing from side to side. Men, who as a rule are much more 

 active and capable of enduring fatigue, have narrower pelves. 

 Two opposed adaptive agencies, therefore, have been at work, 

 one to widen the woman's pelvis, and the other to narrow it. 

 Similarly as regards the child, one adaptive agency has tended 

 to enlarge its head so that it may be intelligent, and the 

 other to reduce its head so that it may be capable of being 

 born. Between them these agencies have brought about a 

 close correspondence in size between the head and the pelvis. 

 Moreover, Nature has adopted the device of uniting the bones 

 of the head by means of a loose membrane, so that in difficult 

 parturition they override one another, whereby the shape of 

 the head is altered and its size reduced by the amount of 

 fluid squeezed from the brain into other parts of the body. 



535. The parturitions of savage women resemble those of 

 the lower animals in their comparative ease, the mother often 

 resuming her duties immediately after birth. As a rule the 



general terms that offspring tend to reproduce, in greater or lesser degree, 

 the characters in which their parents agree, and to regress towards the 

 specific or ancestral type in characters in which they disagree. This 

 amount of knowledge enables us, within wide limits, to produce any type 

 of plant or animal we please, and is quite sufficient to enable us to 

 undertake selective human breeding. Whether it is right or practicable 

 to undertake it is another question. Personally I do not think it 

 expedient that the drunkard or the lunatic should reproduce his type. 

 The question of practicability depends altogether on a diffusion of a 

 knowledge of heredity amongst medical men, and through them amongst 

 the public. Consumption will grow no worse unless an era of good 

 sanitation is followed by one of bad sanitation an unlikely event. 

 The drink problem will be solved by Nature, if not by us and even in 

 spite of us. But the problem of lunacy will grow in magnitude and 

 terror till men are forced to deal with it in a scientific way. Selective 

 human breeding, in so far as certain types must be forbidden to repro- 

 duce themselves, is a dire necessity, and therefore a certainty in the 

 future. 



