154 THE ENZYME THEORY OF DISEASE [CH. xi 



and typhoid fever. Eyre and Washbourn (1899) showed in the 

 case of the pneumococcus that such an alteration in character 

 could be brought about, in one direction, by a single passage 

 through an animal and the reverse change with almost equal 

 facility. We have no explanation of the processes upon which 

 such changes in character depend but we know that many of 

 the conditions which bring them about are precisely those 

 which foster or destroy other properties in organisms which 

 we believe to depend on ferment action (vide infra). 



2. In the second place, there is the observation that the 

 pathological lesions and clinical symptoms resulting from, and 

 characteristic of, infection by a certain organism may be faith- 

 fully reproduced as a result of infection by a totally different 

 organism. For example, we have noted (vide pp. 99 et seq.) 

 some of the lesions and symptoms of diphtheria to be caused 

 by the pneumococcus, those of scarlet fever and of influenza 

 by M. catarrhalis, those of cerebrospinal fever by the Klebs- 

 Loeffler bacillus, by M. catarrhalis and by B. typhosus, and 

 those of rabies by the Klebs-Loeffler bacillus. 



The description of the last example given a case of 

 rabies due to infection by the bacillus of diphtheria will 

 bear repetition. It was recorded by Head and Wilson (1899). 

 The diagnosis of rabies was founded on the history and 

 clinical symptoms. " The well authenticated history of a bite 

 on the cheek by an animal, the two months' incubation 

 period, the onset with extreme pain and numbness in the 

 region of the scar, the development of the characteristic 

 laryngeal and respiratory spasms on attempting to take 

 liquids, the spasm at first being slight but later more pro- 

 nounced and towards the close again feeble or absent, the 

 insomnia, the absence in the beginning of fever which later 

 in the illness became pronounced, the rapid pulse at all 

 stages, the attacks of violent delirium interspersed with 

 periods of calm and complete rationality, the absence of all 

 symptoms pointing towards any other simulating disease and 

 the fatal termination all serve to make an almost complete 

 picture of rabies. " The Klebs-Loeffler bacillus was isolated 

 from the ventricular fluid and detected in the nerve cells of 



