to a generation by heredity, subject of course to the law of 

 variability so far as individual characteristics are concerned. 

 To return, however, to the further consideration of the 

 diseases of the respiratory system as subject to the influence 

 of heredity, I may regard pulmonary phthisis as a typical 

 constitutional disease occurring in persons of the scrofulous 

 diathesis. When considering the diatheses I was careful to 

 point out that their development, in the great majority of 

 cases, required many generations in which to accomplish it, 

 for they are in reality peculiarities of health amounting to 

 morbid tendencies which have been accumulated and inten- 

 sified in their long descent so that we can now recognise 

 them as types of constitutions with which are generally asso- 

 ciated certain well-known forms of disease. Of these dia- 

 theses which were termed universal, because they are not 

 only as old as the race, but because every individual is more 

 or less subject to their influence, are the scrofulous and the 

 catarrhal ; there is surely, therefore, no occasion to prove 

 transmissibility ! These may co-exist or be blent in varying 

 proportions in different individuals, and it may be stated as 

 an axiom that the more the scrofulous diathesis preponder- 

 ates, the greater the danger of catarrhal attacks in an 

 individual. Mr. Hutchinson has well defined scrofula as a 

 permanent and heritable condition, favouring chronicity in 

 all inflammatory processes, and directing them towards more 

 or less specialised ends ; and catarrh, as inflammatory con- 

 gestion excited, in a reflex manner, through the influence 

 of cold applied to the surface : therefore, whatever is the 

 result of " catching cold " is catarrhal. He says : " The 

 susceptibilities of the nervous system, however, in this 

 direction differ, as we all know well, very greatly in different 

 individuals. These differences are hereditary, and may 



