CH. xi] THE ENZYME THEORY OF DISEASE 155 



the medulla. The recognition of this organism was complete 

 and beyond doubt. "Not less suggestive of rabies than the 

 clinical history were the results of subdural inoculations in 

 rabbits with emulsions prepared from the medulla of the 

 patient. There occurred the long period of incubation (20 

 and 21 days) followed by phenomena similar to those in 

 experimental rabies of rabbits, and other rabbits inoculated 

 subdurally with the medulla of the first rabbits behaved in a 

 similar manner." B. diphtheriae was demonstrated after 

 death in the medulla of the rabbits. By a thorough investiga- 

 tion, full details of which are given, infection by the virus of 

 rabies was definitely excluded. 



Such phenomena become intelligible on the supposition 

 that both the lesions and the symptoms of a disease result 

 from the activity of particular enzymes which are usually 

 associated with one particular organism but are capable of 

 being associated, under certain conditions, with an altogether 

 different organism. 



3. In the third place, representatives of one specific 

 organism, morphologically and culturally indistinguishable 

 from one another, may give rise in the living body to entirely 

 different lesions and symptoms. Indeed, the contrast between 

 the train of lesions and symptoms produced in one case and 

 that produced in another may be as marked as the contrast 

 between the lesions and symptoms produced by two organisms 

 representing two distinct species. 



For example, different epidemics of the same disease may 

 present altogether different features. Thus, strains of B. 

 influenzae, morphologically and culturally indistinguishable 

 from one another, may give rise to epidemics of " influenza " 

 characterised by symptoms resembling in one epidemic a 

 simple coryza, in another epidemic rheumatic fever, in a third 

 typhoid fever, and in a fourth cerebrospinal meningitis. 



Not only do different epidemics present different types of 

 disease but individual cases occurring in the course of one 

 and the same epidemic, and undoubtedly due to infection by 

 the same organism, may exhibit a totally different train of 

 symptoms. We have mentioned elsewhere, the account given 



