On Red-ivater or Texas Fever. 



113 



animals, will certainly infect, and may even kill, although after a some- 

 what extended period of time. 



Very important corroboration of this is furnished by the experience 

 of inoculation for red-water, which has lately been adopted in the Cape 

 Colony. Four animals which were immune to red-water (three by reason 

 of having had the disease and recovered, and one by being born and 

 reared on permanently infected veld) were sent from Fort Beaufort to 

 Queenstown to be used by the veterinary surgeon there for inoculation 

 purposes. The animals to be used for inoculation had been " fortified," 

 i.e., re-inoculated with virulent blood, seven weeks previously. 



Twenty animals were inoculated with defibrinated blood from one 

 animal, the doses used being 10 to 20 c.c, according to age. All had 

 a febrile reaction and some slight symptoms of the sickness, but easily 

 recovered. From one of the other of the four animals blood was taken 

 and used to inoculate seven head, giving closes of 10 to 15 c.c. These 

 also all had a reaction, but made good recovery. 



On November 1st the four animals were re-inoculated with virulent 

 red-water blood, and in each case 5 c.c. was injected intravenously and 

 10 c.c. subcutaneously. Twenty-nine days later they were bled. With 

 this blood two lots of cattle were inoculated. 



One lot consisted of 107 animals which had not ever been exposed to 

 red-water infection. The doses used were increased beyond those 

 which I had recommended, namely, 10 to 25 c.c. were used, according 

 to age. Of these animals no less than seventeen died of characteristic 

 red-water. The remainder made a good recovery. 



The second lot consisted of fifty-three head of cattle, all of which, 

 with one exception (an imported animal) had been born and reared on 

 red-water veld. The imported animal was the only one which showed 

 any signs of reaction, but it made a good recovery. 



This experience has sufficed to show that it is not always safe to 

 exceed the doses which I have recommended, unless the animals which 

 have been used for withdrawing blood have been untouched for at 

 least a considerable number of months. 



I have been able, with the co-operation of several farmers, to carry 

 out experiments by which inoculated cattle have been fully exposed to 

 infection at later dates. In May, 1898, I inoculated ten head of old 

 cattle with blood from an animal which had been inoculated, six months 

 previously, with virulent blood. These cattle were immediately removed 

 from the Institute, and later sent to an infected area in company with 

 ten head of young animals which were uninoculated, but, as is com- 

 monly known in this colony, are not so liable to death from this dis- 

 ease as are older animals. Of the young stock all have been infected 

 by exposure in the veld, and , three have died. Of the older, more 

 susceptible, animals not one has shown the slightest signs of illness, 

 and the cows have given birth to healthy calves. 



VOL. LXV. . K 



