THE CAUSATION OF DISEASE. I 3 I 



is wrought into a high pitch of irritability. Every tissue in 

 her body is, in fact, at this time, modified, and the nervous 

 system forms no exception. Wherefore it happens that de- 

 pressing mental shocks are doubly apt to depress the pregnant 

 woman, and thus the mother's health suffers, and through it 

 that of the child. The effect on the latter is probably wrought 

 through the mother's blood, which must necessarily suffer from 

 any great disturbance in nervous action. Owing to this 

 irritable state of the nervous system in the pregnant woman, 

 it rarely happens that she passes through the period of child- 

 carrying without some fright or trouble, so that little difficulty 

 is found by believers in maternal impressions in accounting for 

 any peculiarity in the child that may happen to be present. 



Although it is not easy to conceive of any other ways by 

 which the mother can impress her child, it is, of course, open 

 for any one to assert that there are unknown agencies — powers 

 quite beyond the reach of discovery — capable of bringing about 

 this result ; and, however improbable such a view may seem 

 to us, we are not justified in rejecting it unless we can prove 

 that certain results can be explained on either of the methods 

 mentioned. 



Let us first inquire how the child may be influenced through 

 the mother's blood. A rich and abundant supply of blood — 

 and the quantity will chiefly depend upon the size of the 

 placenta — will necessarily lead to a larger and better nourished 

 foetus than one that is poor and scanty. We may be quite 

 sure that this early difference in blood-supply will leave an 

 impress upon the embryo which will be felt throughout 

 the whole ensuing life. No matter how perfect the post- 

 partum environment, it cannot compensate for such an imper- 

 fect blood-supply. If the foundation of the young human 

 being be not properly laid, it is impossible to erect thereon a 

 solid, well-built structure ; patch it up as we may, the funda- 

 mental weakness will be for ever showing itself. In regard to 

 the nature of the mother's blood we must remember, how- 

 ever, that the foetus is, in some respects, a parasite upon the 

 mother, and will appropriate the nutritive elements of the 

 maternal blood far more vigorously and abundantly, relatively 

 to its size, than the mother ; so that an intensely emaciated 



