HORSE SICKNESS. 479 



tion of liquor sanguinis into the tissues immediately underneath 

 the skin of the head and neck. Consequently these forms are 

 never quite pure. 



" In the blue tongue variety, symptoms of pneumonia are not 

 very prominent. The muzzle, lips, and tongue become swollen. 

 The tongue also assumes a dark-blue appearance. It turns cold, 

 and often becomes too large to be retained in the mouth. Thick, 

 dirty saliva falls from the mouth " (Wiltshire). The blue colour 

 of the tongue is due to congestion of the veins of the part. 



ANIMALS ATTACKED.— The disease appears to be practically 

 limited to the horse tribe (equidse). Donkeys and mules are less 

 susceptible than horses, and zebras are seldom if ever attacked. 

 " I have recently identified a disease which occurs to a limited 

 extent among cattle as being probably of the same nature, while 

 a disease which occurs widely throughout the Eastern Pro^'ince 

 among high-bred goats and sheep is closely related in its pathology 

 with this malady " (Edington). Rickmann showed by experi- 

 ments on himself and others, that human beings are not susceptible 

 to horse sickness. 



GEOGRAPHICAL DISTRIBUTION.— It appears to be confined 

 to Africa, and attacks horses in all parts of the southern portion of 

 that continent. It occurs every year in the Transvaal and 

 Rhodesia; but in Cape Colony, Orange River Colony, and Natal, 

 it takes a widely-spread (epizootic) character only in certain years, 

 although a few cases may be found annually, here and there, in 

 these parts. 



HISTORY AND MORTALITY.— The following outbreaks have 

 been recorded: 1780-81, 1819, 1839, 1854-55, 1891-92 (Cape 

 Colony), 1888 (Natal), and 1893-94: (Orange River Colony). The 

 loss of horses is very great during an outbreak of this malady. In 

 1854-55, 64,850 horses died of it, and in 1891-92, 13,979 horses 

 and 149 mules. Edington tells us that in Rhodesia the annual 

 loss is about 90 per cent. 



The lung form is fatal in at least 99 per cent, of the cases. 

 In fact, many persons who had a wide experience of horse sickness 

 told me, when I was in South x4.frica, that they never knew a 

 case of the lung form recover. The other varieties are said to be 

 less dangerous to life, although the mortality from them is 

 veiy high. 



SEASON OF APPEARANCE.— In Cape Colony and Orange 

 River Colony it rarely occurs before February, although in 1892 



