September 8, 1905.] 



SCIENCE. 



293 



animal diseases. Ladies and gentlemen, if 

 this is so, I have no hesitation in saying 

 that this is the maddest sort of economy 

 and the shortest-sighted of policies. 



Metliods of Comhating the Disease. — 

 During the last three years an immense 

 amount of work has been done in the elu- 

 cida,tion of this disease — how the animals 

 are infected, how the poison is spread from 

 the sick to the healthy, and so on. In 1903 

 Professor Koch was asked by the South 

 African colonies to study this disease, in 

 order to try to find some method of arti- 

 ficial inoculation or some other means of 

 prevention. He did his work in Rhodesia, 

 and especially directed his energies towards 

 discovering some method of preventive in- 

 oculation. At first it was thought that he 

 would be successful in this quest, as in his 

 second report he announced that he had 

 succeeded in producing a modified form of 

 the disease by direct inoculation with the 

 blood of sick and recovered animals. As 

 you are all aware, the only method of con- 

 ferring a useful immunity upon an animal 

 is to make it pass through an attack of the 

 disease itself, so modified as not to give rise 

 to above a few deaths in every hundred 

 inoculated. This is the method that has 

 been employed in such diseases as rinder- 

 pest, anthrax, pleuro-pneumonia and many 

 other diseases. The great difficulty in- this 

 disease in finding a method of preventive 

 inoculation is the fact that the blood of an 

 affected animal does not give rise to the 

 disease in a healthy one when directly 

 transferred under the skin of the latter. 

 It is only after its passage through the body 

 of the tick that the parasite is able to give 

 rise to the disease in a healthy animal. It 

 is evidently, on the face of it, difiicult to so 

 modify the parasite during its sojourn in 

 the tick's body as to reduce its virulence to 

 a sufficient degree. 



Professor Koch in his third and fourth 



reports recommended that cattle should be 

 immunized by weekly or fortnightly in- 

 oculations of blood from recovered animals, 

 extending over a period of five months. 

 Even though this method of Koch had 

 given the desired result, viz., that it ren- 

 dered the inoculated cattle immune to the 

 disease, it is evident that the method itself 

 can hardly be made a practicable one on a 

 large scale in the field. The expense and 

 trouble of inoculating cattle on twenty dif- 

 ferent occasions would be very great. It 

 is apparent now that Professor Koch fell 

 into error through mixing up east coast 

 fever with ordinary redwater. His plan 

 of preventive inoculation was, however, 

 tried on a large scale in Rhodesia by Mr, 

 Gray, now the principal veterinary sur- 

 geon, Transvaal, and found to be useless. 

 At present, therefore, we must look to some 

 other means of preventing the disease and 

 driving it out of the country than pre- 

 ventive inoculation. 



Dipping. — Much can be done to prevent 

 the spread of this disease by ordinary 

 methods. For example, in the case of 

 Texas fever in Queensland dipping cattle 

 in solutions of arsenic or paraffin, in order 

 to destroy the ticks, has met with very fair 

 success; but in the case of this disease we 

 can not expect to get as good results as in 

 the case of redwater. The species of tick 

 which conveys Texas fever remains on the 

 same animal through all its moults, instead 

 of falling to the ground between each dif- 

 ferent one. If it is not possible to spray 

 or clip cattle oftener than once in ten or 

 fifteen days, it is evident that ticks may 

 crawl upon such animals, become infected, 

 and drop off every three or four days, and 

 so escape destruction by the dipping solu- 

 tion. At the same time every infected tick 

 that is killed by spraying or dipping opera- 

 tions is a source of infection destroyed. 



Fencing of Farms. — Again, the fencing 



