22 SCIENCE BULLETIN, No. 21. 



only the control sheep should die in any number. As a matter of fact, 

 during both seasons the mortality in these paddocks from all causes was 

 not more than 2-5 per cent., and there was the same low percentage of 

 deaths in the controls as in the vaccinated animals. As remarked, this 

 tremendous reduction of the average mortality from black disease was not 

 expected to be seen in the unprotected as well as the protected animals, and 

 although the owner (who informed me that he had known the particular 

 station for twenty-six years and in one of the experimental paddocks the 

 mortality averaged 25 to 30 per cent, each season), was satisfied so far as 

 losses were concerned, it did not solve the question as to whether the 

 vaccine was efficacious in the prevention of black disease. I think the real 

 explanation of the great drop in the incidence of the disease in the par- 

 ticular paddocks is that the owner during the summer preceding the vac- 

 cination, had thoroughly drained the swampy places, so that the water from 

 the springs could readily get away, and consequently the carriers of the 

 disease had disappeared to a great extent. 



Experimental vaccination can be carried out in the laboratory at any 

 time of the year, but the real test of the value of such work lies in its 

 application in the field on a large scale, but owing to the seasonal character 

 of black disease, this can only be carried out once a year, because no matter 

 when the immunisation was made, one would have to wait until the end 

 of the black disease season before any conclusions could be drawn as to ite 

 efficacy. If it were unsuccessful for any reason, then one would have to 

 wait another year before undertaking a fresh series of field experiments on 

 a large scale. It follows that such work cannot be accomplished quickly. 



The research work in general has been prolonged for a variety of reasons ^ 

 the strictly seasonal character of the disease (February to May being the 

 usual period), the distance from Sydney (more than 300 miles to the 

 locality of the disease), and the writer being engaged in teaching duties 

 as well as carrying out bacteriological and pathological work for the State 

 at the same time. Perhaps what has handicapped one most of all is the 

 total absence of skilled technical assistance, all work, whether in the 

 laboratory or the field, having in this respect to be carried out unaided. 

 Those who have had to do with the preparation of culture media, cultures,, 

 sections, &c., will appreciate what this means. Finally, in view of the 

 pitfalls which other workers have fallen into, it was very desirable that one 

 should take more than usual precautions in order not to make the same or 

 other errors. 



The identity or non-identity of Black Disease with the Braxy-like 

 disease of Sheep in Victoria and Tasmania, and Braxy or Bradsot. 



It has not yet been established that the above diseases are identical. 

 Several statements in the affirmative have been made, but these are merely 

 opinions, and a definite decision as to whether the diseases are the same or 

 not can only be arrived at by a comparison of the causal organisms, when 



