21.— ON THE PRODUCTION OF A MALARIAL FORM OF 

 SOUTH AFRICAN HORSE-SICKNESS. 



By Alexander Edington, M.D., F.R.S.E., Director of the 

 Colonial Bacteriological Institute, Cape Colony. 



In my Report as Director of the Bacteriological Institute for the 

 year 1901, I have detailed at considerable length experiments having 

 to deal with the production of a malarial form of Horse-sickness. 

 1 propose to summarize these details, and to recount in a brief form 

 additional investigations which have been made to confirm the fore- 

 going, and to eliminate every possibility of fallacy. 



THE PRODUCTION OF A MALARIAL FORM OF HORSE- 

 SICKNESS. 



During my earlier experiments, devised with the object of deter- 

 mining a method of protected inoculation against Horse-sickness, it 

 may be remembered, I showed that donkeys could be inoculated 

 with virulent Horse-sickness blood without being seriously affected 

 thereby. 



Also the remarkable fact was demonstrated that the blood of 

 such donkeys, drawn about the tenth or eleventh day subsequent to 

 inoculation, was capable of setting up a very modified fever in which 

 remissions and intermissions were conspicuously noteworthy. 



In the case of two horses inoculated with donkey blood, I 

 observed one or two of the blood corpuscles to be infected with a 

 parasite having a resemblance to the microbe of Texas fever (Red- 

 water). 



At that time I was led to suppose that the febrile attack induced 

 by the donkey's blood had lowered the animal's resistance, and per- 

 mitted it to acquire an infection of Red-water, to which horses in a 

 good state of health are not susceptible. 



Nevertheless I was never satisfied with such an explanation, and 

 determined at a future date to make a further inquiry in order to 

 ■elicit the truth. 



More recently I published a method by which I had been able 

 to " salt " some horses by means of a mixture of serum and preserved 

 virulent blood. 



During these experiments, however, it was noticed that the 

 most startling differences were noticed, in different horses, in their 

 resistance to the action of this virulent mixture. 



I, therefore, determined upon carrying out special investigations, 

 and, primarily, to reproduce experiments akin to those made with 

 the infected-donkey blood. 



