September 15, 1905.] 



SCIENCE. 



331 



veyed through the stomach, for a long time 

 it has been supposed that it must be con- 

 veyed from sick to healthy horses by means 

 of some biting insect. Experiments have 

 been made within the last few years by 

 AVatkins-Pitchford and others in order to 

 clear up this aspect of the question. Horses 

 have been placed in fly-proof shelters in 

 exceedingly unhealthy places, and it was 

 found that in no case did any of these pro- 

 tected horses incur the disease ; whereas 

 horses allowed to feed in the same place, 

 but without any shelter, soon succumbed 

 to the disease. But, up to the present, as 

 far as I am aware, the particular biting 

 fly, mosquito or other insect which is the 

 carrier of this disease has not been discov- 

 ered, and there can be no doubt that one of 

 the most important facts to make out in 

 the etiology of this disease is the discovery 

 of the particular insect which conveys the 

 disease from the sick to the healthy. By 

 this discovery a flood of light may be 

 thrown on the causation of the disease, and 

 some means discovered of combating the 

 disease through the insect, as has been suc- 

 cessful in some instances in regard to the 

 case of human malaria. 



Professor MacFadyean also suggests that 

 experiments are needed to show what is the 

 'reservoir' of the virus. 



Prevention.— AliYiOugh. we have been un- 

 fortunate up to the present in not being 

 able to make out the exact nature of the 

 parasitic cause of this disease, or to dis- 

 cover the exact insect which carries it, a 

 large amount of patient, persevering work 

 has been done within the last ten years in 

 regard to its prevention by protective in- 

 oculation. 



In this important work Bordet, Eding- 

 ton, Koch, Theiler, Watkins-Pitchford and 

 others have labored for many years, and, 

 according to recent reports, with some 

 measure of success. 



Dr. Edington, for example, who has been 

 working at this problem for several years, 

 reports that heart- water is identical with 

 horse-sickness, and that by inoculating 

 mules with heart-water blood he has been 

 able to salt them against horse-sickness. 

 He says that experiments testing this vac- 

 cine show it to be an ideal one. It gives 

 a high protection to the animals inoculated. 

 Its keeping powers are excellent. No ani- 

 mal has died as the result of this inocula- 

 tion, nor has any dangerous symptom been 

 produced. He states that he is not in a 

 position to supply a vaccine for horse-sick- 

 ness in horses, but has every hope of attain- 

 ing this successful end very shortly. 



We must congratulate Dr. Edington on 

 his results, and trust that this method of 

 conferring immunity may prove itself to 

 be successful when put to practical use. 

 For my part, I am somewhat sceptical of 

 Dr. Edington 's methods of immunizing 

 against horse-sickness. I am sure he will 

 forgive my expression of scepticism when 

 I recall to his memory the various methods 

 he has already brought forward, just as 

 optimistically, and which have all been 

 tried and found wanting. 



Dr. Koch has lately recommended a 

 method of immunization against horse-sick- 

 ness. This is the artificial establishment 

 of an active immunity in susceptible ani- 

 mals by gradually increased doses of viru- 

 lent blood, alternated in the early stages 

 of treatment with the injection of serum 

 prepared from the blood of highly fortified 

 salted horses. Mr. Gray reports that the 

 experiments already conducted on these 

 lines show that the process as laid down by 

 Koch requires important modification be- 

 fore the process of establishing immunity 

 against horse-sickness can be of any prac- 

 tical use. 



Mr. Watkins-Pitchford in Natal is also 

 hopeful of succeeding in producing im- 

 munity against horse-sickness. 



