1891.] on Infectious Diseases. 285 



tation, e. g. when beer becomes ropy, the lactic acid fermentation of 

 milk-sugar, when milk becomes spontaneously sour, &c. 



Similarly it has been shown that when animal or vegetable matter 

 undergoes the change known as putrefaction or putrid decomposition, 

 substances are produced which resemble alkaloids in many ways, and 

 which, introduced into the circulation of man or animals, act 

 poisonously, the degree of action depending, cseteris paribus, on the 

 dose, i. e. the amount introduced. These alkaloids — called ptomaines 

 of Selmi — have been carefully investigated and analyzed by Brieger ; 

 they are different in nature according to the organism that produces 

 them, and according to the material in which this organism grows ; 

 neurin, cadaverin, cholin, &c., are the names given to these sub- 

 stances. 



Uecent research has shown that pathogenic Bacteria, i. e. those 

 associated with, and constituting the cause of specific diseases, are 

 capable of elaborating poisonous substances — toxalbumins or toxins, 

 as they are called — not only in artificial culture media, but also 

 within the human or animal body affected with the particular patho- 

 genic microbe. Thus, in anthrax or splenic apoplexy, Hankin and 

 Sidney Martin have shown this to be the case; in diphtheria 

 (Fraenkel and Brieger), in tetanus (Kitisato), similar toxins have 

 been demonstrated. We can already assert with certainty that a 

 microbe that causes a particular disease causes the whole range of 

 symptoms characterising the disease by means of a 'particular 

 poisonous substance or substances it elaborates in and from the 

 tissues of the affected individual. 



Another important fact ascertained about some of the toxic sub- 

 stances produced by the different pathogenic Bacteria was this : that 

 if, after they are elaborated in an artificial culture fluid, and, by 

 certain methods of filtration, are separated from the Bacteria and in- 

 jected into a suitable animal, they are capable of producing the same 

 disease as their microbes, the rapidity and intensity varying with the 

 amount introduced ; so that it became evident that also in the human 

 and animal body the intensity of the particular disease depends, 

 amongst other things, on the amount of poisonous substance elabo- 

 rated by the Bacteria in the tissues. A further important step made 

 was this : that if the poisonous substamce be introduced in such doses 

 that only slight disturbance would follow, and the dose be repeated 

 several times, the body of the animal eventually becomes refractory 

 to the growth and multiplication of the particular Bacteria. 



Wooldridge's researches on septicaemia and on anthrax, Eoux's 

 researches on septicaemia and diphtheria, Beumer and Peiper, 

 Salmon, and many others, have shown the same for a variety of 

 infectious diseases : in all these instances it has been proved that 

 when the chemical products of a specific microbe, elaborated in an 

 artificial culture medium or in the animal body, are injected into a 

 healthy animal, this latter is rendered refractory against the specific 

 microbe, so that, if the specific microbe be introduced into such a 



Vol. XIII. (No. 85.) u 



