54 HEALTH AND DISEASE 



Africa, and appears to be in some way connected with climatic conditions. 

 Its partiality for low, damp regions, especially during heavy rains, and 

 its comparative absence in dry summers, clearly show that wet favours 

 its development. 



In particularly dry summers very little of the disease is observed, 

 but when the seasons are wet and rain continuous then horse sickness 

 prevails. February, March, and April are months during which it is 

 most prevalent. For a long time it was looked upon as anthrax, and 

 having regard to the suddenness with which it sometimes appears, the 

 rapidity with which it runs its course, and the post-mortem symptoms 

 of the malady, such an assumption was not without reason. It was, 

 however, shown by Lieut. -colonel Dunn in 1887, that the anthrax bacillus 

 was not present in the blood, and that whatever the cause of the disease 

 may be, it could no longer be regarded as anthrax. 



Although we have hitherto failed to determine the precise cause of 

 the malady there is no doubt as to the inoculability of it. 



Dr. Edington showed that it could be transmitted by inoculating the 

 blood of a diseased horse directly into the body of a healthy one; but, 

 strange to say, the serous fluid which is effused into the tissues in the 

 course of the disease when inoculated into a healthy horse does not 

 produce it. 



Speaking of the cause, Captain J. T. Coley, C.V.S., in an able article 

 in the Veterinary Record says: — "It is at present undiscovered, but 

 probably is a very minute micro-organism, as under the highest power 

 of the microscope, and with the present methods of staining, it is invisible; 

 and it passes through the best-made filters, as proved by the fact that 

 filtered blood serum (infectious) when injected produces the disease, so 

 also does infectious blood when injected or given per orem. Yet none 

 of the serous fluids infiltered into the tissues as a result of the disease 

 produce it when inoculated. 



" The following are theories and ideas as to the possible modes of infec- 

 tion, viz. ingestion, inhalation, inoculation. At present one is unable to 

 determine if natural infection takes place by only one or more of these 

 channels, but probably all the above methods of infection are concerned 

 in the spread of the disease, as will be gathered from the following results 

 which I have noted. 



" The organism evidently requires heat and moisture for its propagation 

 and vitality, appears to have a miasmatic origin, and to be transmitted 

 by dews, fogs, and winged insects. 



" Ingestion. — Animals which eat dew-laden grass grown in an infected 

 district invariably sufi'er from the disease, but they can eat the same grass 



