232 A STUDY IN HEREDITY 



acters as man ; it may be that much of the physical develop- 

 ment they undergo after birth is due to the effects of use and 

 exercise; but, beyond question, no other animal is mentally so 

 receptive as man. His power of acquiring mental characters 

 {i.e. his memory) is enormous, and so greatly does he depend on 

 it for survival that, as we have seen, his inborn mental characters 

 {i.e. his instincts), except in a few instances, have undergone 

 complete retrogression. His mind, as I have said, is a blank at 

 birth, and it follows, since so much is acquired, that the dis- 

 position and character of every man must be almost entirely 

 acquired, and not inborn, as is usually assumed. Part of the 

 contents of his memory are recognisable {i.e. may be distinctly 

 remembered), but very much, especially all that is acquired 

 during infancy, is not so. We speak of it as "forgotten," but 

 forgotten things, though they can no longer be represented in 

 consciousness, yet leave their impress on the mind. To take an 

 illustration : imagine twin infants in the same cot, one awake and 

 the other asleep; suppose an event happens that alarms the 

 waking child, but leaves the other unaffected ; suppose, again, 

 that subsequently another event, observed by both children, 

 occurs, which, owing to the apprehension and nervous irritability 

 engendered by the previous event, again alarms the first child, 

 and thus increases its irritability, but, because of its previously 

 undisturbed equanimity, again leaves the second unaffected by 

 fear ; imagine this process repeated ; then, though the original 

 cause of fear were quite forgotten, the one child might well grow 

 up of a much more timid and nervous disposition than the other ; 

 in which case every one would speak of the former as naturally 

 {i.e. innately, instinctively) more timid than his brother, though, 

 in fact, his access of timidity would be acquired. 



In practice, owing to the necessity of the case, we act as if 

 we realised that man's mind, his character, his disposition, is 

 almost entirely acquired ; and, therefore, every parent carefully 

 trains his child for a prolonged period, striving, by precept and 

 example, to inculcate fit mental traits, that is, fit knowledge and 

 ways of thinking and acting. Even the savage mother does this, 



