Exceptions to the Law of Heredity. 203 



he, 'is a sort of monster, for in him nature departs from her 

 specific form ; this is the first step in degeneration.' The authors 

 who in modern times have adopted this opinion, attribute these 

 exceptions to various causes, which may be ranged under three 

 heads, according as they act after birth, before birth, or at the 

 moment of conception. 



1. We are inclined to assign but little importance to causes 

 acting after birth, such as diet, climate, circumstances, education, 

 physical and moral influences. They often produce serious effects, 

 but it is not possible for them to produce the radical transforma- 

 tions we are now considering. This proposition, upheld by 

 Bossuet, Helvetius, and by the writers of the eighteenth century, 

 resulted from the philosophy of that period. But there is now no 

 need to prove that spontaneity is not to be explained by external 

 and late-acting causes, and we no longer believe with Helvetius 

 that we can manufacture great men by means of education. 



2. The causes anterior to birth, but subsequent to conception, 

 are all the physical and moral disturbances of uterine existence 

 all those influences which can act through the mother upon the 

 foetus during the period of gestation ; impressions, emotions, 

 defective nutrition, effects of imagination. These causes are very 

 real, despite the objections of Lucas, who attacks them in order to 

 establish his law of spontaneity. We shall see from examples that 

 between inconsiderable causes and their effects there exists an 

 amazing disproportion. 



3. Finally, there are causes anterior to intra and extra-uterine 

 life, which act at the instant of conception. These depend less 

 upon the physical and moral natures of the parents than on the 

 particular state in which they are at the moment of procreation. 

 ' One fact which fully proves the universality of the law of heredity,' 

 says M. de Quatrefages, ' is the frequent transmission from parent 

 to child of the actual and momentary state of the former at the 

 instant of conception. This fact had attracted the attention of 

 physicians and philosophers, but it had been exaggerated. They 

 went so far as to assert that the past history of the parents was as 

 nothing in the constitution of the child, who, according to them, 

 depends altogether on the state of the parents at the^ moment of 

 procreation. On the other hand, modem writers had lost sight of 



