('(i.use of Worvi-Noilnlrs in (Jatlle. 29 



After an interval of o months, the calf in one ^^i the pens mentioned 

 above was killed (as the result of an accidentV and showed no siijn of 

 Onrhocerra anywhere. Two months later the other calf, whieli had been 

 in habitual contact with the second cow. was killed, and also showed 

 no evidence of either free Onrhnrerca or of nodules. 



From these experiments, therefore, one may infer that neither direct 

 contact nor apparently the intermediation of Haeinutopinus vituli or 

 H euri/sfernus or Trirhoderffs sralaris (thouerh this latter would 

 hardly be expected to act as such an agent) can act as a means of 

 transmission of Onchnrerca (jihsoni. 



Tliis apparent failure of direct contact and of the louse to act as 

 ir.tennedian' agencies in the spread of 0. f/ibsnni is extremely interest- 

 ing in the light of what has been stated earlier in this paper concern- 

 ing probable introduction of the parasite in Indian cattle, since as 

 there stated, distribution from the Indian cattle originally introduced, 

 if they were the original hosts, could hardly have taken place other 

 than through the agency of a flying and bitinc: insect, though there 

 are. as pointed out in our previous paper (p. 21) several difficiilties in 

 respect to this means of transmission. 



As regards the apparent absence of embryos from the blood, and the 

 suggested impossibility of transmission therefore by a blood-sucking 

 insect, we may note that Brumpt (p. 457) does not hesitate to suggest 

 in the exactly similar case of 0. roJi'iilus that a specific fly Glossina 

 palpalis is the distributing agent. 



It may be remarked that proof of the intermediation of any flying 

 insect will be impossible without rigorous methods of experimentation, 

 and even then vrill be extremely difficult. So' numerous are the native 

 animals, birds and marsupials, carrying microfilaria in their blood- 

 streams, that only insects bred in a laboratoiy can be used, and they 

 must be forms belonging to the North of Australia, since those found 

 in the southern States are possibly impotent in this respect, while for 

 this and other reasons, including climatic conditions, the experiments 

 must be done in the North, with cattle bred preferably in Tasmania, 

 so as to avoid all possible infection previous to experimentation. The 

 practicability of. and arrangements for, experiments along these lines 

 are now under consideration, and facilities for the same have been 

 asked for from the Federal Government. 



From the scientific point of view it is undoubtedly true that com- 

 plete proof as to the intermediate host would be valuable, but from 

 the practical point of view, we do not anticipate that the results would 

 be of anv material value. We have shown that every probability 

 points to the intermediary host being a fly ; we have also shown 

 previously that in the northern parts of Australia all cattle are more 

 or less affected. When one reflects, therefore, that over the grreater 



