244 REPORT ON METHODS OF RAT DESTRUCTION. 



employed by the Port of London Antboi'ity. The method gives 

 very satisfactory results and could not we think be improved 

 upon. 



Preventive Measures. 



The chief preventive measures, such as the protection of food 

 supplies, the destruction and prompt removal of garbage, the 

 repairing of defective di-ains, and the rat-proofing of buildings, 

 have been preached so consistently of late that it is unnecessary 

 to allude to them further. It must remain with the medical 

 officers of health and other sanitary authorities to see that these 

 conditions ai'e enforced. 



Protection of Picks. 



The building of ricks on rat-proof platforms has been officially 

 recommended. These platforms, however, besides being extremely 

 costly are not easily portable, and as the ricks are annually erected 

 on different sites, this method of protection can only be adopted 

 in rick yards. It has been found by experiment, which we have 

 confirmed, that rats Avill not dig to a depth of more than 2^ feet, 

 and tlierefore all that is needed is to surround the ]'icks with 

 galvanized iron sheets, 5| feet high, dug slightly over 2 feet into 

 the ground. The cost of such an erection would, amount to less 

 than half that of a platform. The sheets are jDortable and would 

 last for many years. 



Increase in the numbers of the Old English Black Rat. 



We ascertained in the course of our investigations that not 

 only had the Common Brown Rat very greatly increased in 

 numbers in recent years, but that since 1910 the Old English 

 Black Rat had become much more abundant, and in London both 

 species are now in some parts living in harmony, not only on the 

 same premises but in the same rooms. On the one floor of a 

 factory in Holboi'n we captured both species of rats, and also 

 •specimens of the Alexandrine Rat — tlie brown variety of Ratitis 

 rattus, and the black variety of Rattus norvegicus. A well-known 

 London rat-catcher. Avho has kept records of his captures, informs 

 me that he is at the present time catching as many Old English 

 Black Rats as Common Rats in localities where, prior to the war, 

 the latter only were found. 



This recent increase in the numbers of the Old English Black 

 Rat is disquieting, and can only be checked by the enforcement 

 of stricter measures for their destruction on incoming vessels. 



