" BRAXY " SHEEP DISEASE IN AUSTRALIA. 597 



But even then something seems to be wanting. We have 

 seen that adult hfe an 1 even old age confers little or no immunity 

 to the bacteria when experimentally introduced into the subcu- 

 taneous tissues, while every attempt to confer the disease by 

 feeding (this applied to Jensen's and to the bulk of Hamilton's 

 experiments also) has failed. The explanation may lie in the much 

 greater liability of young sheep to harbour gastric and intestinal 

 parasites, and that such might introduce the germs into the 

 depth of the mucosa, if not into the sub-mucosa, where they, be- 

 coming freed of air, may readily multiply, seems possible. In 

 this connection it should be observed that in my experience young 

 sheep may harbour considerable numbers of internal parasites 

 without manifesting any symptoms of intestinal derangement, 

 provided their food supply is nutritious and their general comfort 

 attended to. Yet it should be remembered that while the stomach 

 lesions may be very evident the deduction that the gastric mucosa 

 is necessarily the point of penetration is not warranted, for we 

 have seen that experimental cases frequently show marked lesions 

 of the abomasum, while the real site of entrance may only show 

 intense oedema ; therefore intestinal as well as gastric introduction 

 of the bacilli is not to be excluded. Parasites seem rarely to be 

 able to remain long in adult sheen in comparison with young 

 animals, and this may explain their apparent immunity. 



But notwithstanding the above arguments in favour of the possi- 

 bility of alimentary infection, the evidence against is very great 

 — indeed overwhelming. 



Neilsen and Jensen always failed to transmit bradsot by 

 feeding. Hamilton never transmitted it by feeding during his so- 

 called immune season ; and even when he did succeed, his experi- 

 ments were open to the objection of being conducted on naturally 

 infected farms. Likewise, I have not only failed by administering 

 pure cultures in the ordinary way per oram, but even when such 

 cultures were intermixed with numerous glass splinters, which 

 should have favoured, to say the least, the introduction of the 

 bacteria into the gastric or intestinal sub-mucosa. 



Further, these experiments, so far as the Victorian bacillus 

 was concerned, were conducted during the period of the year — 

 the summer months — when the Victorian disease is prevalent. 



The mere failure to produce the disease by these feeding 

 experiments does not of itself disprove the possibility of alimentary 

 infection ; but the fact that by the introduction of small doses {and 

 one cubic centimetre of a liqtiid culture is not a large dose to introduce 

 into the alimentary tract of sttch an animal as a sheep) of virulent 

 bacilli, a decided and active immunity is rapidly produced, does in 

 our present state of knowledge regarding the disease certainly com- 

 pletely disprove the possibility of natural infection by the digestive 

 tract. 



A preliminary experiment seems to indicate that the same 

 holds good of blackleg. 



