THE INHERITANCE OF DISEASE 119 



to-day is that where there is a taint in the family this is 

 likely to be increased by the mating of two such affected 

 individuals, while, on the other hand, with a healthy stock 

 inbreeding seems to have no harmful effect whatever. This 

 is only what would be expected. Remembering the 

 theoretical explanation of disease given in the previous 

 section, it becomes evident that when both parental germs 

 are affected their union will increase the number of diseased 

 chromosomes. But it can hardly be conceived how disease 

 is going to enter the fertilized ovum if neither of the 

 original two parental germ-plasms is affected. As there 

 are hardly any families in which there is not some taint or 

 other, close intermarriages are likely to accumulate the 

 same taint in certain individuals. It is therefore on the 

 whole safer that no close inbreeding take place, unless it 

 can be made certain that the stock is absolutely healthy. 

 In short, consanguinity is harmful in tainted stocks, but 

 harmless in healthy stocks. 



