Septembeb 8, 1905.] 



SCIENCE. 



295 



cidating the causation of this disease, and 

 their work forms one of the most interest- 

 ing chapters in the history of pathological 

 science. They discovered that it was caused 

 by the presence in the red blood corpuscles 

 of a protozoal parasite closely related to 

 the parasite found in east coast fever — the 

 Piroplasma parvum. This organism is 

 called Piroplasma Mgemimim. They fur- 

 ther discovered that this parasite was con- 

 veyed from sick to healthy cattle by means 

 of a tick. They also showed that the cattle 

 born and bred in certain southern districts 

 are immune to the disease, whereas cattle 

 in the northern districts are susceptible. 

 Hence, if southern cattle were driven into 

 the northern district, they gave rise to a 

 fatal disease among the northern cattle; 

 and, vice versa, if the susceptible northern 

 cattle were driven into the southern district 

 among the apparently healthy cattle of that 

 district, they took Texas fever and died. 



Texas fever was introduced about 1870, 

 and is now endemic throughout most of 

 South Africa. For many years the native 

 cattle have been immune to the disease ; 

 that is to say, on account of being born and 

 bred in a Texas fever locality they had 

 inherited a degree of resistance to the dis- 

 ease which enabled them to pass through 

 an attack when they were young, and so 

 they became immune. But there is one 

 peculiarity about Texas fever which does 

 not occur in Rhodesian tick fever, and that 

 is that the blood of an animal which has 

 recovered from Texas fever remains in- 

 fective — the germs remain latent — and so 

 the native cattle of South Africa, although 

 apparently healthy, are capable of infect- 

 ing imported susceptible cattle with this 

 very fatal malady. This is what makes it 

 so difficult to import prize stock into this 

 country. 



When the Boers visited Mooi River, at 

 the beginning of the war, they found a 



prize short-horn carefully stabled in Mr. 

 P. D. Simmon's farm. They killed most 

 of his stock for food, but left this short- 

 horn bull alive. When they left the farm 

 they turned this bull into the nearest field, 

 in order, of course, that it might procure 

 food. They had much better have eaten 

 it. It promptly took Texas fever and died. 



This disease, then, has become of second- 

 ary importance to South Africa in these 

 days. The native cattle have become nat- 

 urally immune, and the disease is only fatal 

 to susceptible imported cattle. This, of 

 course, discourages the importation of prize 

 stock; but with the knowledge we possess 

 it ought to be possible, by good stabling 

 and prevention of contact with tick-infected 

 cattle, to keep the prize stock alive for a 

 reasonable time. The question of the feasi- 

 bility of immunizing the prize stock while 

 calves in England might be considered. 



In regard to methods of conferring im- 

 munity on susceptible cattle many have 

 been tried, but none are absolutely free 

 from risk. 



We may sum up in regard to redwater 

 or Texas fever by saying that our knowl- 

 edge of its causation and methods of pre- 

 vention is much the same as it was ten 

 years ago. The work done by Smith and 

 Kilborne on this disease was of such a bril- 

 liant nature, and was done so thoroughly, 

 that little has been left for later workers 

 to do. 



3. Biliary Fever of Horses, 3Itdes and 

 Donkeys. 



This is a disease of horses, mules and 

 donkeys very similar to redwater in cattle, 

 and is caused by a closely allied parasite, 

 the Piroplasma equi, discovered for the first 

 time in South Africa by Bor.det, Danysz 

 and Theiler, and named by Laveran, of 

 Paris. 



It is similar to redwater, in that animals 

 which have recovered from the disease re- 



