Pyemia and Septicemia. 3 



The native susceptibility of the subject,— horse, ox,— conduces 

 to the disease, while the insusceptibility,— bird— tends to obviate it. 



The debility 0/ the system or of individual tissues attacked, lowers 

 the resistant power, and especially that of leucocytosis, and thus 

 favors survival and encrease of the microbes and their chemical 

 products. Thus the shock succeeding a serious operation, the 

 general depression attendant upon severe illness, or the poisoning 

 by narcotizing ptomaines and toxins, may easily become the extra 

 weight which causes the system to succumb. On the contrary, 

 pre-existing or long standing disease, with consequent general 

 debility appears at times to prove to some extent a protective 

 factor, the previous exposure to the invading germ having edu- 

 cated the leucocytes to resist the toxins and to produce the de- 

 fensive sera which neutralize the latter or keep the invading mi- 

 crobes in check. A measure of immunization has been .secured. 



The resulting immunization cannot be looked on as very per- 

 fect, nor permanent, as a specially strong inoculation by a 

 virulent microbe, or large dose, or different conditions of life, 

 will entirely overcome it, and the pysemic fever appears. Yet 

 in chronic cases of secondary abscesses from a deep source of 

 infection, the resistance is often such as to ward off febrile 

 pyaemia. In a horse with primary ab.sce.ss situated deeply under 

 the humerus, free evacuation and healing of the wound, have, in 

 my experience, been followed by the formation of abscesses in 

 distant points for a period of seven years, but without any 

 marked febrile reaction. 



The complex nature of the infection appears at times to over- 

 come the vital resistance more effectively than will the presence 

 of even a potent microbe alone. Some of the worst cases follow 

 on a wound, the seat of complex infection, and even .saprophytes 

 are to be dreaded in this connection. This may operate in vari- 

 ous ways, either by mutual combinations or decompositions of 

 the toxic products of associated germs producing more deleterious 

 products, or by the individual action of one ptomaine or toxin on 

 leucocytes, hsematoblasts, sera, or tissue, laying it more open to 

 the attacks of those of another microbe which by itself would 

 have been comparatively harmless. 



Koch's experiments showed that the attack is violent in ratio 

 ■with the size of the dose : one- thousandth part of a drop of pysemic 



