94 BACTERIAL POISOXS. 



positive results which some authors have supposed to be 

 due to inoculation with the tyi^hoid bacillus." 



In other words, this eminent author teaches that although 

 other germs may cause the essential symptoms and lesions 

 of typhoid fever in the lower animals, they are not related 

 to the germ found in the spleen of man afler death from 

 typhoid fever, because they do not react in the same man- 

 ner with the anilin stains, and present a different appear- 

 ance in their growths on potatoes. 



We will suppose that in an epidemic of diphtheria, A 

 examines the membrane from a hundred, or we might as 

 well suppose a thousand, children, and finds a characteristic, 

 well-marked, easily recognized bacillus in all. He isolates 

 this organism, and obtains it in pure culture. He inocu- 

 lates animals, and these manifest all the signs, together with 

 the appearance of the characteristic membrane of diphtheria, 

 and in these animals he finds his bacillus growing as in the 

 throats of the children. All the rules of Koch have been 

 complied with. Has_ A demonstrated that his bacillus is the 

 sole cause of diphtheria ? No. He has shown that his 

 bacillus is a cause of diphtheria ; but he has not proven 

 that there may not be other germs, wholly different from 

 his in form and size, which may also cause diphtheria. 

 The most which can be proven by Koch's rules is that a 

 given germ is a cause of a certain disease. They do not 

 show, as most bacteriologists would have us believe, that 

 the given germ is the sole cause of the disease. 



To illustrate, we will suppose that a botanist in visiting 

 Arabia should find a tree producing a berry, the coffee 

 berry, whicli, when properly prepared and taken into the 

 system, produces certain effects which are due to the alka- 

 loid, caffein, and which invariably follow the drinking of 

 a decoction of these berries ; would our supposed discoverer 

 be justified in concluding that the coffee ti-ee is the only 

 plant in the world capable of producing these supposed 

 characteristic effects ? Should he reach such a conclusion, 

 the fact that it is not warranted would be shown by a study 

 of the tea plant of China and the guarana of South America. 



The moment that it is granted that the real poison of the 



