151 



Brooks (R. St. J.). The Influence of Saturation Deficiency and of 



Temperature on the Course of Epidemic Plague.— J^ of Hygiene. 



Cambridge. Plague Supplement v, issued 19th May 1917, pp. 881- 



899, 18 charts. 



The conclusion arrived at is that, while the combined efiects of 



temperature and saturation deficiency have in the majority of cases 



an influence on the incidence and course of plague epidemics, yet 



under certain conditions such epidemics come to an end at a time 



when the climatic conditions are presumably favourable for a 



continuance of the disease. In these cases other factors come into 



plav, and attention is directed to the work of the Advisory Commission 



in connection mth the seasonal breeding of rats, the decrease in the 



numbers of rats during epidemic periods, and the accompanying 



increase in the proportion of immune to susceptible rats. The adverse 



influence of high temperature and saturation deficiency may be 



explained by their effect on the duration of life of the rat flea, 



Xenopsylla cheopis, when separated from its host. 



The author's summary is as follows : Plague does not maintain 

 itself in epidemic form w^hen the temperature rises above 80° F. 

 accompanied by a saturation deficiency of over -30 of an inch. Plague 

 epidemics are rapidly brought to an end in the presence of a high 

 saturation deficiency, even when the mean temperature throughout 

 and after the termination of the epidemic has been considerably below 

 80° F. Plague epidemics may commence and increase in intensity 

 when the mean temperature is well above 80° F., provided that the 

 saturation deficiency is below -30 of an inch. In some districts in 

 India and in certain tropical islands {e.g., Java, Mauritius), where the 

 climatic conditions are favourable at all times of the year to the 

 incidence and spread of plague, the disease may occur at any season. 



Wenyon (C. M.) & O'CONNOB (F. W.). An Inquiry into Some 

 Problems affecting the Spread and Incidence of Intestinal Protozoal 

 Infections of British Troops and Natives in Egypt, with special 

 Reference to the Carrier Question, Diagnosis and Treatment of 

 Amoebic Dysentery, and an Account of Three new Human Intesti- 

 nal Protozoa. Part iv. Experimental Work with the Human 

 Intestinal Protozoa, their Carriage by House-flies and the Resist- 

 ance of their Cysts to Disinfectant and other Agents.— Ji. R.A.M.C., 

 London, xxviii, no. 6, Jime 1917, pp. 686-698. 



This paper records much experimental work with the house-fly as 

 a carrier of human intestinal protozoa. Flies feeding on faeces were 

 found readily to take encysted and other forms of protozoa into their 

 intestines ; these may remain as long as 42 hours in the intestine if 

 the flies are prevented from feeding, or may be passed from the gut 

 as early as five minutes or as late as 20 hours after feeding [see this 

 Reinew, Ser. B, v, p. 117]. Flies infected in this way will deposit the 

 material on any kind of food, and it seems that the wide distribution 

 of human protozoal infections in warm countries can best be explained 

 in this way. Wild flies captured in Alexandria often deposit cysts of 

 protozoa and eggs of worms which they have evidently taken up 

 from human dejecta on which they have fed. Cysts of Entamoeba 

 histolytica will survive in water, but are killed instantaneously by 



