HORSE SICKNESS. 469 



at all hours, early and late, without the night air having any bad 

 effect on them. South African race horses generally go out in the 

 early morning when the dew is on the grass. The experience of 

 a large number of South African farmers I consulted, is greatly 

 in favour of keeping horses, during an outbreak of this sickness, 

 in a stable or even in a kraal, if it be intended to turn them out 

 to graze, until the sun has dissipated the dew off the grass, saj' 

 until eight o'clock in the morning. They have told me that keep- 

 ing horses in a kraal for this object is quite as good as stabling 

 them. A kraal is simply a walled-in enclosure, which, being con- 

 stantly trodden, down by cattle and horses, has little or no grass 

 on it. Horses may be ridden or driven through the night, or, if 

 wearing a nosebag, may be left at rest in a badly-infected area 

 without becoming infected. 



It may be reasonably assumed that drinking water does not act 

 as a carrier of this disease; because in the foregoing cases of 

 immunity and infection, no difference in the drinking water was 

 made. Water has been taken from pools in horse sickness areas 

 during a season of epidemic, and examined microscopically, but 

 without success. Under the supposition that the spores under a 

 protean guise might be present among the debris and multitudes 

 of animalculse with which such waters abound, horses have been 

 inoculated with as much as 10 com., but without any result 

 accruing. 



Infection by inhalation may apparently be excluded, for there is 

 abundant evidence to show that' the disease is not communicated 

 by simple cohabitation of healthy and diseased horses. 



It may be safely concluded that the infective agent of horse 

 sickness, like that of anthrax (p. 458) and tetanus (p. 511), can 

 live, multiply, and retain its virulence outside the animal body, 

 supposing that the conditions of climate are favourable to its 

 existence and development. 



The above statements warrant us in excluding worms, ticks, and 

 blood-sucking flies from the list of producers of this disease. 

 Arguing against the malarial character of horse sickness, it has 

 been pointed out that there have been instances of great mortality 

 from it in one district, while the adjoining one, separated only by 

 a narrow river, has been almost entirely exempt. 



The effects of moisture and heat are well marked in this 

 disease. Horse-sickness occurs mostly in low-lying parts of the 

 country, independently of the fact that the general locality may 

 be considerably elevated above the sea^level. Thus, Johannes- 

 burg, which is about 6,000 feet above the searlevel, is frequently 

 subject to its baneful influence. It is commonly observed to occur 

 during periods when the. air has become humid and been associated 



