THE CAUSATION OF DISEASE. 1 67 



ganizing the brain (and this is out of the sphere of practical 

 causation) we might, no doubt, render any given individual 

 insane ; but who would engage to induce in this or any other 

 way the many different kinds of insanity from which man 

 suffers ? For the diseases of mind are" many and subtle, and 

 we may lay it down as a fact that individuals exist in whom 

 it would be impossible to induce any given variety of insanity. 

 The following instance of the same disease affecting twins 

 is interesting, inasmuch as the relative shares taken by 8 and 

 E in causation were probably exactly the same for each indi- 

 vidual. " Dr. Gregory's twin children .... were both seized 

 with croup on the same night, having been walking together in 

 the sunshine during the evening in a cold wind."* There was 

 doubtless some structural peculiarity in these children, which 

 rendered them particularly prone to croup, for it is probable 

 that few others would have contracted the complaint under 

 like external circumstances. A similar instance is the fol- 

 lowing : " I once saw .... twin boys, eight months 

 old, in each of whom a small abrasion formed in the raphe 

 of the perineum, and became covered with membrane. This 

 membrane extended, though unaccompanied by any other local 

 symptoms of diphtheria, to the margin of the anus, and to just 

 within the internal sphincter. Both children died within a 

 week from the commencement of the illness, sickening, as 

 under some grave constitutional disease, with troublesome 

 diarrhoea and exhaustion, which stimulants failed to remove. 

 The identity of this disease with ordinary diphtheria is 

 established beyond doubt." 



• Hilton Fagge, "Practice of Medicine," vol. i. p. 79, quoting Sir T. Watson. 



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