THE RENDERING OF ANIMALS IMMUNE, 119 



vented. When the blood serum of protected animals is added to a solution of 

 venom a distinctly observable reaction occurs, and this reaction may be of 

 significance when considered along with circumstances which will be stated in 

 the remaining part of this communication, and especially with the circumstance 

 that the blood serum is itself almost destitute of physiological activity. This 

 protective substance may be produced in the body by the influence of the 

 venom, but it is also conceivable that the substance is actually a part of the 

 venom itself, which gradually accumulates under repeated administrations, 

 whereas the lethal and toxic constituents of the venom are more rapidly 

 destroyed or eliminated. 



The Blood Sekum op Immunised Animals : Antivenene, 



Having thus succeeded in producing a high degree of protection in animals 

 against the toxic effects of serpents' venom, the blood serum of these animals 

 was, in the next place, collected for the purpose of testing its antidotal pro- 

 perties. A few preliminary experiments were, however, early made with the 

 serum of animals in whom the protection had not been carried to a high 

 degree, and they were sufficient to show that antidotal properties are possessed 

 even by this serum. It soon became apparent that, in order to obtain some 

 reasonable approximation to constancy in the conditions of the experiments, 

 it was necessary that the serum should be in such a state that it would remain 

 unchanged during at least several weeks. It was found that this could be 

 ensured without any appreciable loss of antidotal power by drying the freshly- 

 separated serum in the receiver of an air pump over sulphuric acid, after it 

 had been passed through a Chamberland's filter. A perfectly dry and easily 

 pulverisable solid was thus obtained, which could be kept unchanged for pro- 

 bably an indefinite time, and from which a normal serum could easily be 

 prepared as required by merely dissolving a definite quantity of the dry 

 serum in a definite quantity of water. To this serum, whether in the dry 

 form or in solution, it would be convenient to apply the name " antivenene.'''' 



The greater number of the experiments now to be described were made 

 with antivenene derived from the mixed serum of three rabbits, which had 

 last received a dose of cobra venom equivalent to thirty times the minimum 

 lethal. I avoid the expression " immunised against " thirty times the 

 minimum lethal dose, for, as a matter of fact, an animal is always protected 

 or immunised against a dose considerably above the last which it had received. 



The experiments were so planned as to obtain in three or four different 

 conditions as exact a definition as possible of the antidotal power of the 

 antivenene. Four series of experiments have been undertaken on rabbits ; 

 but all the experiments required to complete two of these series have not yet 

 been made. In one series the venom was mixed outside of the body with the 

 antivenene, and immediately thereafter the mixture was injected under the 

 skin of the animal ; in the second series the venom and antivenene were 



