338 proceedings of section d. 



Life-History. 



That the life-history of these filarige is an extremely difficult 

 and probably complex one is indicated by a number of factors. 

 There is, first of all, the enormous nimiber of eggs and larvae 

 (averaging a million) present at one time in the fertile female, iir 

 addition to which there is the constant expulsion of free larvae. 

 This, compared with the comparatively few adults, fifty at most^ 

 found even in the most severely affected animal, alone demonstrates 

 that the possibility of an individual larva ever attaining maturity 

 is extremely remote. 



Is an intermediary host necessary ? By analogy with allied 

 parasites this may almost be taken for granted. The possibility 

 of a free existence must, nevertheless, be considered. Our observa- 

 tions and experiments negative this supposition. For example^ 

 we have seen the larvae do not live longer than thirty-six hours 

 in normal saline, even at blood heat. Further, larvae sown on plots 

 of grass at about 30" C, in a moist atmosphere, rapidly died, and 

 although frequent examination from twenty-four hours later up 

 to six weeks were made of the grass and soil, nothing that would 

 even suggest a development could be found. Again, on several 

 occasions, we have injected large numbers of living larvae into the 

 subcutaneous and muscular tissues of young cattle. Subsequent 

 post-mortem examination of one, four months later, failed to 

 detect any indications of the development of a worm nodule. 

 Similar results followed the smearing of larvae on the skin of the 

 axilla and groin. It should be noted that in none of these cases 

 larvae could be detected in the blood after inoculation. Desiccation 

 of the larvae, at blood heat, causes their death in at least twenty- 

 four hours. These observations and experiments seem to answer 

 our question in the affirmative : an intermediary host is reqmred 

 in the development of these filariae. 



Possible Intermediary Hosts. 



Carnivora, e.g., Native Dogs [Dingo), Station Dogs, and Wild 

 Pigs. — These may be excluded. Even the native dog never 

 attacks healthy cattle, and rarely, if ever, devours the carcases 

 of bullocks. Cattle dogs on the stations are few, and rarely 

 accompany the men ; the amount of fresh meat with the exception 

 of offal they secure is extremely small, and briskets are seldom, if 

 ever, thrown to them. It would be difficult under any circum- 

 stances for any dogs to secure the living parasites. 



Wild pigs, which are numerous in some coastal stations, may 

 also be excluded. In any case, we have seen a carcase opened 

 and left lying in the vicinity of a wild-pig camp and remain un- 

 touched by these animals. 



Ticks. — The ticks may be likewise disposed of. The nodules 

 were observed long before the advent of the tick in Queensland, 

 and are numerous on many stations where the tick is unknown. 

 In any case it is unlikely that the large larvae of the filariae would 



