BACTERIA IN DIPHTHERIA. 363 



slightly swollen spleen, sometimes fatty degenerations in the liver, 

 kidney, and myocardium. We have always found the Loffler ba- 

 cilli at the seat of inoculation, most abundant in a grayish-white, 

 fibrino-purulent exudate present at the point of inoculation, and be- 

 coming fewer at a distance from this, so that the more remote parts 

 of the osdematous fluid do not contain any bacilli " (Welch and Ab- 

 bott). The authors quoted agree with Loffler and others in stating 

 that the bacillus is only found at the point of inoculation. In all 

 cases their cultures from the blood and from the various organs gave 

 a negative result. 



Rabbits are not so susceptible and may recover after the subcu- 

 taneous inoculation of very small doses, but usually die in from four 

 to twenty days when two to four cubic centimetres of a bouillon 

 culture have been introduced beneath the skin. In these animals 

 also there is an extensive local oedema, enlargement of the neigh- 

 boring lymphatic glands, and a fatty degeneration of the liver. 

 Roux and Yersin have shown that in these animals, when death 

 does not ensue too quickly, paralysis of the posterior extremities fre- 

 quently occurs, thus completing the experimental proof of the spe- 

 cific pathogenic power of pure cultures of this bacillus. 



Similar symptoms are produced in pigeons by the subcutaneous 

 inoculation of 0. 5 cubic centimetre or more, but they commonly re- 

 cover when the quantity is reduced to 0.2 cubic centimetre (Roux 

 and Yersin). 



The rat and the mouse have a remarkable immunity from the 

 effects of this poison. Thus, according to Roux and Yersin, a dose 

 of two cubic centimetres, which would kill in sixty hours a rabbit 

 weighing three kilogrammes, is without effect upon a mouse which 

 weighs only ten grammes. 



Old cultures are somewhat less virulent than fresh ones, but when 

 replanted in a fresh culture medium they manifest their original 

 virulence. Thus a culture upon blood serum which was five months 

 old was found by Roux and Yersin to kill a guinea-pig in five days, 

 but when replanted it killed a second animal of the same species in 

 twenty-four hours. 



Evidently a microorganism which destroys the life of a suscepti- 

 ble animal when injected beneath its skin in small quantity, and 

 which nevertheless is only found in the vicinity of the point of in- 

 oculation, must owe its pathogenic power to the formation of some 

 potent toxic substance, which being absorbed gives rise to toxaemia 

 and death. This inference in the case of the diphtheria bacillus is 

 fully sustained by the results of recent experimental investigations. 

 Roux and Yersin (1888) first demonstrated the pathogenic power of 

 cultures which had been filtered through porous porcelain. Old 



