QLTESTIOXS XEEDIXG ELUCIDATION. 285 



very large dose of this powerful drug to give to a healthy horse, 

 and probably cannot be given in every case without setting up 

 inflammation of some of the internal organs, with falling away in 

 condition, and general debility " (p. 64). 



After giving details of live experiments made to determine 

 the point, the author sums them up with the following observa- 

 tion : — "From these experiments it may be concluded that 

 arsenic is quite useless as a prophylactic agent, but that it is 

 useful in prolonging life and usefulness in the Fly Country after 

 the disease has begun" (p. 66). 



"10. — Concluding Remarks" (pp. 66-69). 



After discussing the various ways in which an infective 

 disease may be attacked, the author goes on to say : — 



" To return to Nagana, what do we know of the disease ? 

 We know that it is caused by the entrance into the blood of a 

 minute parasite whicli multiplies there and causes death ; that 

 this parasite exists in the blood of many animals and that it is 

 conveyed from animal to animal by the Tsetse-fly, or by the 

 eating of the raw flesh of animals affected by the disease. We 

 also know that the disease is limited to certain tracts of country 

 having certain physical features, but that its distribution in 

 these ti'acts is very variable. 



" We do not know how the parasite causes death, but surmise 

 that it may do so by the poisonous action of some substance or 

 substances elaborated or secreted by it, or by producing a pro- 

 gressive lijemolysis and antemia, leading to a form of auto- 

 intoxication. We do not know all the animals in which this 

 para.site may exist, but judging from the number of domestic 

 animals in which it is fatal, we may consider that it has a wide 

 range. It may exist not only in the koodoo, wildebeeste, and 

 other big game, but it may also exist in the wild cats, rats, birds, 

 and even flsh of the Fly Ccjuntry. 



" We do not know whether there are other species of fly which 

 convey the disease besides the Tsetse, but this perhaps is a minor 

 consideration. We do not know of any metliod at present of 

 isolating the hypothetical poisonous substance elaborated by the 

 hiematozoon so as to be able to study it or to render animals 

 immune to it by gradually increasing doses. No experiments 

 have, as far as I am aware, been made in this country in the 

 direction of studying the effect of the serum of animals in whose 

 blood the ha^matozoa have been numerous. Dr. Lingard has, 

 however, made a few with a negative result in Surra " (p. 67). 



Remarking that treatment of disease by means of serum "is 

 very popular at present, "the author proceeds to quote in exienxo 

 tlie results of Dr. Lin^ard's experiments on : — " The subcutane(jus 

 inoculation of blood and its derivatives in its different forms, 



