its Pailiolorjy and Methods of Protective Inoculation. 305 



Since one animal, after the first inoculation, had a severe reaction, it 

 is evident that the limit of strength, consistent with safety, had been 

 reached. The reactions, in the two cases, after the second, were 

 extremely severe, and indicate that the limit of strength of virus for 

 that inoculation had been slightly exceeded, if a widespread scheme 

 of operation had been intended to be carried out among animals in 

 the open. 



These results would seem to indicate that fortified serum, e.g., that 

 obtained from animals which, after " salting," have been reinoculated 

 with large doses of virus, exerts a peculiar and definite action on the 

 virus. 



While, however, 100 c.c. of serum suffices to prevent 1 c.c. of virulent 

 blood, when mixed with it, producing any great elevation of tem- 

 perature, I have referred to a case in which a severe reaction was 

 produced. Since, in another case, 200 c.c. of the same serum, with an 

 equal amount of virulent blood, was followed by a reaction and a 

 definite amount of protection, it is evident .that the difference in 

 susceptibility between the latter animal and those which react slightly 

 after 100 c.c. of serum and 1 c.c. of virulent blood is equal to 100 c.c. 

 of fortified serum. Moreover, as already shown, when the virus is 

 attenuated by its passage through less susceptible animals, such as the 

 donkey or cow, its effect, when used in the same dose, either by sub- 

 cutaneous or intravenous injection, varies very greatly in different 

 animals ; in some producing no evident reaction, in others setting up 

 some fever ; while, again in others, its use was f ollowed by the onset 

 of the virulent disease resulting in death. 



If, therefore, the admixture of serum with virulent blood is followed, 

 on inoculation, merely by a modified form of the disease, it must be 

 concluded that the serum, of itself, cannot be credited with this result, 

 but that a peculiar quality, existing in the animal body, and varying in 

 amount from animal to animal, must play an important part. Whether 

 this principle is a simple body, or is a combination of several, cannot at 

 this moment be determined, but for convenience' sake I would suggest 

 that the name " Antagones " should be applied to it. The term need 

 not be taken to imply either an antitoxic or germicidal body, but 

 merely to denote the " defensive " properties which are already existent 

 to a greater or less degree in all animals, or are produced or increased 

 under special stimulation. 



Since thoroughly " salted " animals and donkeys can be reinoculated 

 and infection proved to exist in their blood for at least ten days sub- 

 sequent, I am inclined to look upon the protection existing in " salted " 

 animals as of the nature of a " tolerance," and to believe that true 

 immunity, in horses, against this disease is never acquired. 



VOL. LXVII. 



