147 



of 179 cases only 34 could positively declare absence of 

 family taint. Dr. Theodore Williams says the principal 

 effect of the predisposition is to be seen not in any peculiarity 

 of the symptoms, but by the influence it exercises over the 

 age of attack, which is much earlier in those predisposed 

 than in others. 



Regarding phthisis as a disease essentially belonging to 

 those which are dependent upon an inherited predisposition, 

 and as the concurrence of several conditions is usually 

 necessary for the development of chronic diseases, we must 

 differentiate between those conditions which are inherited 

 and those which may be acquired. Of the former we must 

 recognise a congenital defectiveness of resisting power, which 

 although not synonymous with weakness, may be associated 

 with it. This is generally manifested in the children of 

 weakly parents, or of closely-related inter-marriages, or when 

 there is a marked dissimilarity in the respective ages of the 

 father or mother, or when repeated pregnancies have followed 

 each other in rapid succession. " Usually in such persons 

 one or several parts of the body are again and again the seat 

 of disease, and form the locus minoris resistentia. If this be 

 situated in the respiratory organs, frequent and long-con- 

 tinued catarrhs of the nose, larynx, and air-passages occur, 

 and perhaps give rise ultimately to pulmonary diseases which 

 develop into phthisis." 1 This condition is essentially trans- 

 missible, as is also scrofula, another of those conditions 

 which usually concur in the production of chronic diseases. 



There is a point of some importance to which I should 



have referred before, and which I may now be permitted to 



allude to, especially as it exercises a modifying effect upon 



the influence of heredity generally, and to a great extent 



1 Ruehle, Opus cit. 



