PROPHYLAXIS 



1433 



is reached, at which it is allowed to remain for four hours. For the 

 fumigation of ships it is found to be much more satisfactory if the gas 

 is made to circulate and to penetrate better by means of electric fans 

 and similar devices. This gas kills rats, rat-fleas, and other insects, 

 and plague bacilli, and, if dry, will not injure food-stuffs, except fruit 

 and some vegetables, nor will it harm merchandise or machinery. 

 A mixture of equal parts of cyllin and petrol constitutes a reliable 

 pulicide and bactericide. 



Rats may also be killed b}^ means of Danysz's virus, which is a 

 bacillus easily recognized from Bamllus pesfis, and kills the rat by a 

 septicaemia, causing oedema of the intestinal walls, infiltration of 

 Peyer's patches, and enlargement of the spleen, with sometimes 

 peritonitis, and only then enlargement of the lymphatic glands. 

 Danysz's virus is administered, by Simpson's method, on bread, and 

 is said not to affect human beings, though recently complaints of 

 illness of persons living in places where some sort of virus was being 

 used has been recorded. Danysz's and similar viruses are very 

 often inert and inefficacious in the tropics and require to be exalted 

 by passage through animals before being used. 



Bannerman has strongly advised cats as a method of rat 

 extermination, but it must be noted that cats are not refractory to 

 plague. 



It appears to us that Black's methods of dealing with an outbreak 

 of plague are the best. First of all, he localizes the outbreak, and 

 begins his prophylactic measures in a circle well outside this area, 

 and works towards the centre. This is of great importance, because 

 beginning in the centre and working towards the periphery merely 

 disseminates the disease. Secondly, he has recognized the fact 

 that rats will not eat food handled by human beings, and therefore 

 the people who handle and cut the bread into cubes prior to dipping 

 it into poison have their hands smeared with oil of aniseed, as is also 

 the board on which the bread is cut. The poison which he has used 

 with great success is phosphorus paste. The phosphorus is mixed 

 with glucose to prevent spontaneous combustion, and then a paste 

 is made with a fatty base such as lard, but it is advisable to vary 

 from time to time the fatty base. To our minds these little points 

 make all the difference between failure and success. Liston advises 

 the centralization and isolation of the stock of grain in villages, 

 and an organization of the system of the refuse disposal, while 

 the stabling of cattle in houses should be prohibited. He lays 

 stress on the disinfection of the clothes of travellers coming from 

 infected areas. Traps equivalent in number to 2 per cent, of the 

 population should be used to catch rats. 



With regard to the destruction of fleas in human habitations, 

 washing the floors and walls with crude oil emulsion such as the one 

 recommended by Burke will be found useful, as demonstrated by 

 Jackson and others. Burke's formula is crude oil 80 parts, whale- 

 oil soap 20 parts. The preparation is a jelly mixing freely with 

 water, and a 10 per cent, solution of it will destroy fleas with 



