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THT] AORICULTUBAL JOURNAL. 



toms are noticed — is probably witboiit 

 significance, as the same swelling over 

 the eyes is produced when the animal is 

 infected artificially by means of the 

 hypodermic syringe. 



Another point of conjecture in this 

 theory of mosquito-produced horse-sick- 

 ness is the species of insect. 



Analogy with the malaria-carrying 

 mosquito points strongly to the various 

 kinds of anopheles, and perhaps to some 

 species of the ordinary mosquito or 

 eiilex, as being possible bearers of the 

 disease. 



Anopheles are known to be present 

 over most of the horse-sickness districts 

 of South Africa, and it is probable that 

 further investigation would prove their 

 widely spread distribution throughout 

 the whole continent. 



This insect, which should be recog- 

 nised by everyone as a possible menace to 

 health, can be distinguished without 

 much difficulty from the ordinary mos- 

 quito, by the existence of spots ■ — or 

 maculae — upon the wings when held up 

 to the light, and also by the in- 

 sect's peculiar attitude when resting 

 upon any object, for it appears 



to stand witli tne proooscis, wnicii 

 is in a line with the body, touch- 

 ing the surface, and the posterior part of 

 the body elevated at a considerable angle', 

 by reason of the length of the hind legs.' 

 The ordinary mosquito, it will be noticed, 

 rests with its body almost parallel with 

 the surface upon which it alights. 



Modern science has within the last few 

 months shown the imperative necessity 

 of keeping all person suffering from 

 malarial fever closely guarded against 

 the attacks of those anopheles, as it is 

 in this manner chiefly if not solely that 

 the disease is communicated to others. 

 This short digi'cssion is not entirely 

 inappropriate to the subject under con- 

 sideration, as I have oliserved the 

 anopheles feeding u])n horses, both in 

 health and sickness, and have noticed 

 them abstracting blood from their host 

 until greatly distended. 



There remains further, when consider- 

 ing this insect theory of the disease, the 

 possibility of the agency of other than 

 the winged insects — such as members of 

 the arachnidae or ixodiae (spider and 



tick family) — being concerned. There 

 seems, however, no evidence, direct or 

 indirect, to point to the likelihood of an 

 intermediarv active agent being found 

 amongst these orders. The whole weight 

 of experience goes to show that the hours 

 between sunset and sunrise are more dan- 

 gerous than the hours of daylight, that 

 moist or marshy places are particularly 

 to be avoided, that rain is followed by a 

 period of immunity, that enveloping ani- 

 mals with smoke "increases their safety, 

 and that the cause of the disease is cap- 

 able of rapid transmission ivom place to 

 place. This comljination of evidence 

 would seem to negative the agency of 

 such comparative immobile insects as 

 ticks, spiders, etc., whose habits cannot 

 satisfy the equation under consideration. 



In concluding this brief review of the 

 possible connection between the punctur- 

 ing insect and South African horse-sick- 

 ness, the fact should again be recalled 

 that the foregoing theories and sugges- 

 tions are of a speculative and tentative 

 nature, and put forward rather with the 

 object of tabulating and bringing before 

 our review a resume of our experiences 

 rather than with the idea of setting forth 

 a scientific thesis, capable of untying the 

 Uordian knot wliieh has puzzled us so 

 long, and this theoiy (the Subcutaneous 

 or insect Agency theory), is put forward 

 with more hesitation, as up to the pre- 

 sent* it has rrceivcd no notice at the 

 hands of workers with the disease, except 

 in the instance quoted above, in which 

 insects were accjuilted of being concerned 

 in the production of the disease. 



(B.) The Rcxpiralonj Theory (or the 

 theory dealing witli the probability of a 

 horse" becoming infected by inspiring' 

 the germ of the disease.) 



Here again there is an absence of 

 direct evidence tending to prove the pro- 

 bability of the above theory. That such 

 a mode of entry of the organism is pos- 

 •sible is almost conclusively proved by the 

 fact that injections of virus or infective 



* Thia short rhuma of South African Horse- 

 sickness was written on board ship, during the 

 writer's sirk leave, in the autumn of last year, 

 and is published now for the rea';ons given in 

 the introductory article on this subject in the 

 Journal. 



