442 BIOLOGY. [Book ti. 



It is easy enougli to explain why a particular man, having 

 otherwise little intelligence, is nevertheless endowed with this 

 or that sensitive aptitude. It is enough that the external ear 

 be well shaped, the nucleus of the optic layer which corresponds 

 with it voluminous, the fraction of cortical substance in relation 

 with this nucleus rich in cells, in order that the individual, 

 though otherwise ill endowed, should have musical aptitudes. 

 We thus comprehend singular facts, which have seemed abnormal 

 to many observers ; for example, that many idiots have shown a 

 taste and even an aptitude for music. 



The importance of these generalisations will escape no one. 

 They shed light upon the most obscure, the most mysterious 

 domain of biology. They snatch psychology from the hands of 

 dreamers to give it a true scientific basis j they undermine a 

 number of deeply-rooted prejudices, of myths illegitimately 

 revered ; they are the true and solid foundations upon which the 

 science of the moral man will one day rise. 



