XII. 



BACILLI WHICH PRODUCE SEPTICAEMIA IN 

 SUSCEPTIBLE ANIMALS. 



WHEN, as a result of accidental (natural) or experimental inocula 

 tion, a microorganism is introduced into the body of a susceptible 

 animal which is able to multiply in its blood, producing a general in- 

 fection, we speak of this general blood infection as a septicaemia. 

 When pathogenic microorganisms which are unable to multiply in 

 the blood establish themselves hi some particular locality in the ani- 

 mal body which is favorable for their growth, and by the formation 

 of toxic products, which are absorbed, give rise to general symptoms 

 of poisoning, we designate the affection toxaemia. As examples of 

 this mode of pathogenic action we may mention diphtheria and 

 tetanus. As a rule, the various forms of septicaemia are quickly 

 fatal, and, as the microorganisms to which they are due multiply in 

 the blood of the infected animal, this fluid possesses infectious pro- 

 perties, and, when inoculated in the smallest quantity into another 

 susceptible animal, reproduces the same morbid phenomena. A typi- 

 cal example of this class of diseases is found in anthrax, to which 

 disease a special section has already been devoted (VII.). But in 

 this and other forms of septicaemia subcutaneous inoculations do not, 

 as a rule, result in the immediate invasion of the blood by the para- 

 sitic microorganism. Often a local inflammatory process of consider- 

 able extent is first induced ; and in some cases general infection only 

 occurs a short time before the death of the animal, depending, per- 

 haps, upon a previous toxaemia from the absorption of toxic products 

 developed at the seat of local infection. The pathogenic action, then, 

 in acute forms of septicaemia appears to result, not alone from the 

 presence and multiplication of the pathogenic microorganism in the 

 blood, but also from the toxic action of products evolved during its 

 growth. 



Some of the pathogenic bacilli of this class now known to bac- 

 teriologists have been discovered by studying the infectious diseases 

 induced by them in lower animals among which these diseases pre- 

 vail naturally i.e., independently of human interference. Many 



