UK I. A THX TO INKKCTIOUS DISEASES. 93 



tributed in the animal in which tin- disease has Ix-en 

 induced. 



Let us give <>nr special attention to the first of these 

 rules for a few moments. What is meant by the state- 

 ment that the special germ must be found in every case of 

 the disease? How will A, pursuing his studios on the 

 bacteriology of a given disease in America, decide whether 

 or not a bacillus which he finds is identical with one which 

 \\:\< Keen reported as invariably present in the same disease 

 by B, who has investigated an epidemic in Germany? 

 What means are relic* I upon to prove the identity of these 

 two organisms? The means which have lxx i n relied upon 

 wholly are the form, si/e, reaction with staining reagents, 

 manner of growth on various nutrient media, and, in ex- 

 ceptional instances, correspondence in their effects upon the 

 lower animals. In other words, with the exception of those 

 instances in which the effects upon animals are tried, the 

 characteristic property by which the germ causes the disease 

 is left wholly out of consideration. It is admitted that any 

 causal relation which the germ may have to the disease is 

 due to its capability of forming one or more chemical poi- 

 sons, and yet no attempt is made to ascertain whether or 

 not it possesses this property. Indeed, some of the most 

 eminent bacteriologists have taught that in the identifica- 

 tion of germs the reactions with staining reagents and the 

 appearance of the growths on the various nutritive media 

 are of more importance than the observation of the effects 

 upon animals. Thus, FLUGGE says : 



" Inoculation experiments with both typhoid dejections 

 and pure cultuns of the Elx-rth bacillus have universally 

 Ix-en without success. 'Flic few experiments in which a 

 typhoid disease has followed inoculation or feeding have 

 Ixvn made with impure material containing other active 

 bacteria. It is known that a group of widely distributed 

 organisms, which, however, a/v wholly different from the 

 typhoid bacillus, have the power, when injected snlx-n- 

 taneonsly or intravenously, of producing in animals death 

 with marked swelling and nlccration of Peycr's patches. 

 To these organisms undoubtedly arc due the apparently 



6* 



