209 



Although the usual history of a plague outbreak traces back to an 

 antecedent epizootic among rats, notable exceptions occurred in 

 Manchuria in 1910, in the Philippine Islands in 1912, and in Colombo 

 in 1914. Even where the phenomenon of an antecedent rat epizootic 

 is found, the earlier manifestations are not infrequently obscured. 

 The supervision of the rat population should include systematic 

 bacteriological examination of rat carcases and determination of the 

 presence or absence of Xenopsylla cheopis and other rat-fleas, together 

 with an examination of the bacterial content of the parasites. 



Pneumonic plague is exclusively conveyed from man to man, 

 whereas bubonic plague is spread by rats. The advisory committee 

 on plague in India has summarised the position with regard to infection 

 by rat fleas as follows :— (1) Multiplication of the plague bacillus takes 

 place in the stomach of the flea. (2) The average capacity of the 

 flea's stomach is 0-5 c. mm. On this basis a flea imbibing the blood 

 of a plague rat might take 5,000 germs into the stomach. (3) The 

 approximate proportion of fleas in the stomach of which the multi- 

 plication of plague bacilli takes place varies with the season of the 

 year, being 6 times greater in the epidemic than in the non- epidemic 

 season. (4) Plague bacilli are present in the rectum and faeces of 

 fleas taken from plague rats and such faeces are infective to guinea-pigs, 

 l)oth by cutaneous and subcutaneous inoculation. (5) During the 

 plague season, fleas might remain infective for 15 days after imbibing 

 infective blood, but during the non-epidemic season no individual was 

 infective after the 7th day^ (6) A single flea of either sex may transmit 

 the disease. (7) The plague bacillus has never been seen in the body 

 cavity or salivary glands of infected fleas. In the Dutch Indies, fleas 

 have been shown to be infective up to 28 days. [For investigations 

 relating to the bionomics of the rat-flea see this Review, Ser. B, ii, 

 pp. 62-64, 131 & 190.] 



Differences of opinion exist concerning the presence of rats on board 

 vessels and their relative ability to surmount difficulties of transit to 

 shore. Mus deciwianus appears to be a better swimmer than M. rattus 

 and easily crosses a distance of 200 to 300 yards in smooth water. 

 M. decumanus is inferior to M. rattus and M. alexandrinus as a climber 

 and jumper, but all three species are adepts at sheltering themselves 

 in small spaces. Certain goods imported into Australia, e.g., oil-cake 

 in sacks, bamboo poles in bundles covered with matting, loose hemp 

 in bnndles, etc., aft'ord places of concealment. The internal protection 

 of vessels against access of rats to food-stuffs and edible refuse is a 

 problem which requires constant attention. The use of small meshed 

 wire netting is an essential feature of such operations. 



Place (F. C). Flies, a Factor in a Phase of Filariasis in the Horse.— 

 Adelaide, N.D. 7 pp. [Received 11th September 1915]. 



Investigations made by the author in India during 1898 resulted 

 in the discovery of a connection between certain flies and a form of 

 cutaneous filariasis of the horse. One of the chief sites of infection 

 was shown to be the glandular tissue of the eyelids, especially the 

 membrana nictitans. Since 1910 the frequency with which neoplastic 

 growths of the eyelids of horses has been observed in Australia, and 



