MICROBIAL DISEASES OF MAN AND DOMESTIC ANIMALS 8oi 



The toxaemia probably arises from lysis of the organisms and it has been 

 shown that the autolysis of cultures in salt solution gives rise to a soluble 

 toxic portion and an insoluble non-toxic portion. 



Immunity to Pneumococcus infections can be shown to exist after an 

 attack but only for a short time. 



Pneumococci may be considered as inhabiting the mucous mem- 

 branes of the respiratory tract in the majority of people and acquire 

 virulence only under some special circumstances lowering the general 

 vitality. In pneumonia and some kinds of bronchitis as above men- 

 tioned it should be remembered that sputum and mouth spray may 

 contain large numbers of virulent organisms. 



Specific therapeutic agents such as antipneumococcic sera, vac- 

 cines of dead cultures and autolysates, as well asleucocytic extracts, have 

 been tried and all with some promising results. The earlier failures 

 with serum therapy have been found to be due in part to the occurrence 

 of different strains. Four strains or types are now recognized. About 

 one-third of cases is due to Type I, one-third to Type II, 10 to 15 per 

 cent to Type III and the remainder to Type IV. Under ordinary 

 conditions the mortality of Type I and II is 25 to 30 per cent, of Type 



III 59 percent, and Type IV 10 to 15 per cent. The corresponding 

 antisera are more successful in Type I infections. 



The prophylaxis of Pneumococcus infections lies in general hygienic 

 measures, in the destruction of sputa and avoidance of possible infection 

 by mouth spray, etc. In households in which pneumonias existed due 

 to Types I and II, Stillman isolated the organisms from the dust in 

 43 per cent and 59 per cent respectively. Occasional carriers of 

 Types I and II are found not associated with clinical cases. Type 



IV predominates in the mouths of the healthy. 



ANTHRAX* 

 Bacterium anthracis 



Also called splenic fever or charbon; and in man, wool-sorter's dis- 

 ease or malignant pustule. 



The disease has been known for centuries. It is thought that it was 

 one of the plagues of Egypt, mentioned as a murrain on beasts, and boils 

 and blains on man and beast. The first accurate characterization of 



* Prepared by P. C. Harrison. 

 51 



