CLIMATOLOGY 



1423 



Sputum in invisible droplets containing viable plague bacilli was 

 frequently to be found in the air near a patient. Teague and Barber 

 have shown that the fine droplets of sputum disappear very quickly 

 unless there is a considerable amount of aqueous vapour in the 

 atmosphere, as is found in very cold climates, and hence the ten- 

 dency for pneumonic plague to spread in those rather than in warm 

 climates. On the other hand, the bubonic or septicsemic is not 

 spread from man to man, but from rats to man. The epizootic 

 is the real disease, and the epidemic is only an offshoot. 



The above aetiology explains fully the predisposing causes of sex, 

 women staying more in the house than men ; of house, of season, of 

 chmate, and also the carriage of the disease from one place to 

 another by people, fodder, grain, bales of cotton, and clothing, 

 rags, etc. 



Verjbitski in 1908 showed that bugs could act as carriers of the 

 bacilli, and this has been confirmed by Jordansky and Kladnitsky, 

 while Walker considers Clinocoris rotundatus to be one of the 

 carriers of plague in India, having found 22 per cent, infected with 

 B. pestis when collected from infected native huts. Moreover, he 

 successfully transmitted the disease from man to the rat by means 

 of Clinocorus rotundatus. 



The possibility of lice acting as occasional carriers should not be 

 forgotten. Lice caught on patients suffering from plague have at 

 times been found infected with B. pestis. 



In California, Wherry, McCay, and others have shown that the 

 ground-squirrel {Citellus beecheyi) is subject to plague, and that its 

 commonest flea, Ceratophyllus acutus Baker, is the vector from 

 squirrel to squirrel, and, further, that this flea will bite man. 

 Further, they record a subacute case of plague in a boy where the 

 infection was believed to be acquired by contact with ground 

 squirrels. With regard to the outbreak in Manchuria and North 

 China, Gray has shown that it started among men who handled the 

 tarbagan [Arctomys hohak Miiller), which is susceptible to epizootic 

 plague, and that these men on returning to their homes introduced 

 the disease into three provinces, as pneumonic and septicaemic 

 plague, while it was spread by the agency of the breath and personal 

 contact of clothes and belongings by coolies travelling in parties 

 and sleeping together in overcrowded insanitary inns, especially 

 as the cold of the winter induced an indoor existence. These 

 travelling parties infected adult males who stayed at the inns or were 

 travelling, and so it spread to the ordinary population. No infected 

 rats could be found, in 20,000 examined, while isolation of the 

 patients and their contacts, together with efficient disinfection, were 

 sufficient to diminish the death-rate. This shows how important 

 the pneumonic form of plague may be in epidemics, especially in 

 cold weather, but it is also to be noted that, although it starts from 

 association with an epizootic, it tends to die out without being suc- 

 ceeded by a bubonic outbreak, but it may infect rats and so cause 

 a bubonic epidemic. There has been an epizootic in Suffolk, in 



