AND ENVIRONMENT 15 



Other in the psychical as well as the physical characters. 

 Common environment can hardly give husband and 

 wife the same eye-colour, nor the same stature, nor 

 length of cubit — these were determined before marriage. 

 Yet their resemblance in these matters is about the 

 same as in their temper or temperament. Secondly, if 

 resemblance in tuberculosis be due solely to infection, 

 how are we to explain the resemblance in eye-colour or 

 insanity ? Are these due to infection also ? 



Thirdly, I recall the very remarkable point we have 

 already considered. Dr. Goring, as we have seen, has 

 worked out the degree of resemblance with regard to 

 phthisis between husband and wife, among all poor and 

 among the better class of poor. Adding my result we 

 have the following : 



Husband and Wife All Poor — -oi 



„ „ Prosperous Poor +-i6 



„ „ (Pearson) Middle Classes +-24 



„ „ (Dr. Williams) Professional Classes + -28 



It would thus appear, either that like mates with like 

 more commonly in the more intellectual classes, or that 

 infection is more likely to occur in middle class than in 

 poor households. I think there is not the least doubt 

 that much of the relatively small resemblance of husband 

 to wife in the matter of phthisis is due to a selective 

 influence and not to infection at all. This selection is 

 largely an intellectual one and has no existence among 

 the very poor. 



The matter is so important that we determined to 

 take out from our family records all pairs of husbands 

 and wives and then inquire how far phthisical stock is 

 attracted to and mates with phthisical stock. 



