302 Mr. A. Kdington. South J//-//-"// II 



3. Its germicidal activity is extremely weak, as is shown by the 

 following experiments : 



(<i.} 1 c.c. of fresh virulent blood was mixed with 100 c.c. of serum. 

 and after being kept for twenty-four hours in the ice chest 

 was inoculated into a clean horse. The animal had a sharp 

 febrile reaction. 



(li.) Another animal was treated in the same way, but the serum and 

 blood was injected immediately after being mixed. This 

 animal also had a reaction, but less severe than the former. 

 Variation of susceptibility must of course l>e taken into account, 

 and, in order to establish this conclusion satisfactorily, a con- 

 siderable number of animals would require to have been simul- 

 taneously dealt with. 



(c.) Equal volumes of serum and preserved blood were mixed and 

 kept at ordinary room temperature for four days. Of this 

 mixture, 2 '5 c.c. was injected subcutaneously into a clean 

 animal. Fever set in after the usual period of incubation, 

 pursued its characteristic course, and the animal died under 

 circumstances and in the usual time which obtains after the use 

 of pure virulent blood. 



Since 1 c.c. of virulent blood mixed with 100 c.c. of serum pro- 

 duced a sharp febrile reaction in one animal but had practically no 

 effect in some others, and since 1 c.c. of blood and 200 c.c. of serum 

 produced a reaction in another animal, it was clear that under this 

 method also I should have to meet differences of animal suscepti- 

 bility. 



It was so far fortunate that preserved virulent blood acted equally 

 well as fresh blood, so that a standard virus is easily prepared and 

 maintained, and by mixing the serum of a considerable number of 

 animals I am able to standardise a large volume of serum. 



I concluded, therefore, to determine the amount of serum which, 

 when mixed with a definite amount of blood, would serve, acting in 

 concert with the natural protective bodies in the system of the average 

 horse, to ensure the production of the modified disease. After fourteen 

 days should have elapsed subsequent to this inoculation, provided a 

 severe reaction was not set up, I intended to re-inoculate with the same 

 dose of virulent blood, but with a much reduced quantity of serum. 

 Again, after fourteen days, the procedure should be repeated, the dose 

 of virulent blood remaining a constant quantity, but the dose of serum 

 l>eing still further reduced. Finally I intended to inoculate with 

 virulent blood by itself. 



In the first three series of experiments sixteen horses were used. 

 These were inoculated as follows : 



