x.] DISEASE. 171 



the hereditary tendencies in each person to disease 

 being usually very various, it is by no means always 

 that useful forecasts can be made concerning the health 

 of the future issue of any couple. 



Consumption. 



General Remarks. — -The frequency of consumption 

 in England being so great that one in at least every six 

 or seven persons dies of it, and the fact that it usually 

 appears early in life, and is therefore the less likely to 

 be forestalled by any other disease, render it an appro- 

 priate subject for statistics. The fact that it may be 

 acquired, although there has been no decided hereditary 

 tendency towards it, introduces no serious difficulty, 

 being more or less balanced by the opposite fact that it 

 may be withstood by sanitary precautions although a 

 strong tendency exists. Neither does it seem worth 

 while to be hypercritical and to dwell overmuch on the 

 different opinions held by experts as to what constitutes 

 consumption. The ordinary symptoms are patent 

 enough, and are generally recognized ; so we may be 

 content at first with lax definitions. At the same 

 time, no one can be more strongly impressed than 

 myself with the view that in proportion as we desire 

 to improve our statistical work, so we must be in- 

 creasingly careful to divide our material into truly 

 homogeneous groups, in order that all the cases con- 

 tained in the same group shall be alike in every 

 important particular, differing only in petty details. 

 This is far more important than adding to the number 



