120 REPORT OF THE BUREAU OF ANIMAL INDUSTRY. 



The rabbits inoculated from the original culture, after remaining at 

 the temperature of 43.5-44 C. for ten and twenty days, died from the 

 inoculation disease, but those inoculated from the same tube after 

 thirty and forty-three days remained permanently well. This was 

 not due to an attenuation of the culture but to its death. Turning 

 to the series of rabbits inoculated from the cultures renewed every 

 five or ten days, those receiving culture liquid ten, twenty, and thirty 

 days old died from the inoculation disease, while one inoculated after 

 forty-three days remained alive, because the culture was dead, i. e., 

 it failed to fertilize fresh tubes after repeated inoculation. An adult 

 guinea-pig, inoculated from the same culture material thirty days 

 old, died in 12 days as a result of the infection. In this case only a 

 few drops had been injected. This experiment demonstrates that in 

 general the pathogenic power of hog cholera bacilli is only destroyed 

 by the death of the organisms themselves. This is a very important 

 fact. It will be remembered that in the attenuation of anthrax 

 bacilli, their virulence was gradually diminished and a time was 

 reached when they failed to kill all but mice, while they still retained 

 the power of multiplying in nutritive liquids. In the above experi- 

 ments even guinea-pigs, which are less susceptible to this disease 

 than rabbits, died twelve days before the culture was found dead. 

 The latter may have been dead some days before this, for no tests 

 were made meanwhile. 



This fact has an important bearing upon the nature of the path- 

 ogenic activity of hog cholera bacilli. It shows that there are two 

 elements involved, (1) the ptomaine action of the organism ; (2) 

 their mechanical effect. That there is a ptomaine action of these 

 bacilli has been conclusively proved in the experiments of the Bureau 

 made upon pigeons several years ago. But this ptomaine action is 

 evidently secondary to the mechanical effect of the bacilli in forming 

 plugs or thrombi in the blood vessels and thus causing destruction 

 of tissue by impeding the circulation. This tendency to act me- 

 chanically is not lost as long as the bacilli are alive, as shown by 

 their fatal effect on rabbits and guinea-pigs shortly before they them- 

 selves are destroyed. 



At the temperature employed (43.5-44 C.) the original bouillon- 

 peptone culture a died between the twentieth and the thirtieth day 

 after the beginning of the exposure. The culture from this, re- 

 newed at the end of every fifth or tenth day, died between the thir- 

 tieth and forty-second days. Another culture, b (see table), which had 

 been removed from the thermostat after the forty-sixth day and kept 

 at the temperature of the laboratory (about 30-33 C. during July), 

 was still fatal to a rabbit on the fifty-seventh day. Another rabbit 

 inoculated ten days later remained w^ell, and a fresh culture made at 

 the same time remained sterile, showing that the apparent immunity 

 of the rabbit was due to the death of the bacilli injected. This ex- 

 periment also shows pretty conclusively that the pathogenic power of 

 these specific organisms expires only with their life and not long be- 

 fore. 



It is evident from our own experiments and more recent ones made 

 in France and Germany, and conducted on the same lines, that the 

 amount of immunity which we may expect to gain from preventive 

 inoculation will depend on the quantity of ptomaines produced by 

 the specific microbes, i. e., upon their poisonous nature. In other 

 words, our success will depend upon the relation borne by the pto- 

 maine to the disease process. If this factor is very great it is highly 



