.'>00 Mr. A. Ellington. Smith African Horm--sickn(-- 



rxactly the strength of an attenuated vims, it would IKJ 

 necessary always to make the test on at least five animals. 

 4. The indication for future experimentation was thus to call for 

 the discovery of some method by which a virus >f standard 

 virulence might l>e, at will, reduced to any required degree 

 of attenuation. 



Experiments were also made to determine whether the blood of an 

 animal suffering from " secondary " fever had any infective property. 

 To this end animals under "secondary" fever, with temperature 

 as high as 106 F., were bled and the blood used to inoculate clean 

 animals, but in no case was any reaction produced thereby. I there- 

 fore am convinced that the blood during " secondary " fever is non- 

 infective. 



Experiments with Serum and Dejibriiuited Blood of ,-////<//"/.< </////* /*./ 

 recovered from Horse-sick ms.-. 



The experiments made have included serum derived from 



1. Animals formerly "salted." 



2. Animals formerly " salted " and subsequently reinoculated by 



periodic injections of gradually increasing doses of virulent 

 blood, the maximum dose being 1000 c.c. 



3. Animals treated as in Clause 2, but subsequently permitted to 



rest for several months and then reinoculated with a small dose 

 (5 c.c.) of virulent blood. 



Under the first clause, serum was obtained from a well-" salted " 

 animal which had been twelve days, previous to bleeding, inoculated 

 with 5 c.c. of preserved virulent blood. 



Animals which were inoculated with 2 c.c. of virulent blood were 

 subsequently inoculated with large doses of serum (100 c.c. or more). 

 The inoculations, in some cases, began on the day that virulent blood 

 was injected; in others it was delayed until the temperature began t<> 

 rise, but although the total amounts given exceeded 1000 c.c., no 

 definite interference with the course of the disease was noticeable. 

 Under Clause 2, " salted " animals were inoculated with progressively 

 increasing doses of virulent blood. When these animals had been 

 inoculated with doses of virulent blood equal to 1000 c.c. they were 

 allowed to rest for eight to twelve days, after which they were bled. 



Of this serum, 500 c.c. was inoculated at one dose into a horse, 

 which, during thirty-three subsequent days, manifested no signs of 

 illness due to the inoculation. When this period was completed, it 

 was inoculated with virulent virus and as a result died of characteristic 

 horse-sickness. No evidence was shown that the serum had in any 



