MATERNAL IMPRESSIONS 161 



to peas do not seem to be relevant, since the two halves of the 

 pea-seed are of course the cotyledons and part of the embryo. 

 Some of the phenomena seem simply ordinary cases of Mendelian 

 inheritance (see Chapter X.). 



Some of the cases where it is said that the whole fruit is affected 

 e.g. in grapes and oranges well deserve further investigation. 



ii. Maternal Impressions 



It is a time-honoured belief that the mental states especially 

 vivid sense-impressions and strong emotions of a pregnant 

 mother may so affect the unborn offspring that structural changes 

 result which have some correspondence with the maternal ex- 

 perience. The belief was hardly doubted till Blondel began to 

 criticise it early in the eighteenth century. 



Every one allows that the mother's health in the widest sense 

 may react on the offspring, within what limits we hardly know ; 

 but it is a very different matter to believe in definite and specific 

 structural effects. There can be no doubt that the firmly rooted 

 theory is in the main quite unscientific, except in the sense that 

 it expresses the instinct to discover some cause for peculiar 

 phenomena. A child has hypertrichosis : did not the mother 

 look too long at a picture of John the Baptist in a hairy robe ? 

 A white mother has a dark child: what can she say but that 

 she was frightened by a Moor ? 



The abundant literature on the subject has been carefully 

 studied by Dr. J. W. Ballantyne, and it need hardly be said that 

 his general verdict is wholly against the tenability of the theory, 

 except in a very refined form. 



The mental experiences of the mother have been held to ex- 

 plain peculiarities of colour, abnormal hairiness, birth-marks, 

 malformations, and even conception itself. The post hoc ergo 

 propter hoc argument has never been more wildly used, and the 

 result has been a retardation of the study of ante-natal pathology. 



Jacob's trick of using peeled wands to influence the colour of 



ii 



