AND ENVIRONMENT 



21 



Now let us look at the general inheritance — the 

 resemblance between parent and child — for physical 

 characters as shown in Table XI. 



These results suffice to indicate that the intensity of 

 parental resemblance with regard to phthisis is absolutely 

 similar to what we find for insanity or deaf-mutism, which 

 certainly do not arise from infection, and is of the same 

 order as we know occurs in the case of the chief 

 physical characters in man. 



TABLE XI. INHERITANCE OF CHARACTERS IN MAN. 



I turn now to the next stage in my argument. 



If we admit, it will be asked, the view that tuber- 

 culosis is due to the tubercle bacillus, and that this 

 does not arise de novo, then surely the transmission 

 of the bacillus — infection — must be the source of all 

 phthisis. But who has ever denied this ? In my very 

 first paper on the subject I wrote : 



* The discovery of the possibility of phthisical infec- 

 tion has led, I think, to under-estimation of the here- 

 ditary factor. Probably few individuals who lead a 

 moderately active life can escape an almost daily risk 



^ Incomplete family histories. 



