68 SPIROCILETES 



cretions makes it appear probable that these animals are an im- 

 portant means of spreading the disease, and this most readily 

 explains the common occurrence of epidemics in families. Two 

 cases have been reported as having resulted from the bites of 

 rats. That rats serve to spread Weil's disease in Europe also 

 appears evident from its common occurrence where rats are 

 abundant. In Europe butchers are especially prone to it, and 

 severe epidemics of it have broken out in the rat-infested war 

 trenches. 



Treatment and Prevention. The Japanese investigators find 

 evidence that salvarsan is destructive to Sp. icterohemorrhagice, 

 but their results are far from convincing and the German inves- 

 tigators say that salvarsan does not destroy the parasites. More 

 investigation and experimentation needs to be done before this 

 question can be settled. 



Investigators of both countries have had greater success in 

 treating the disease by injection of the serum of a convalescent or 

 of an animal which has become immune. The Germans found 

 the convalescent serum effectual, either as a preventive or for 

 cure, when diluted 100 times. Japanese workers, on the other 

 hand, put far more faith in active immunization. They inject 

 spirochsetes which have been weakened by subjection to very 

 dilute carbolic acid and left on ice for a week. Guinea-pigs can 

 be immunized by such injections, or even by injections of dead 

 parasites or the products of their disintegration. 



Prevention of this disease, as of plague, evidently resolves itself 

 largely into rat destruction by poisoning, trapping and rat-proof- 

 ing. Some reduction should be obtained by keeping food where 

 rats cannot get access to it, and, of course, where it cannot be- 

 come infected, directly or indirectly, by the excretions of human 

 patients. However, since the parasites are able to penetrate 

 directly through thin skin, especially if there are any abrasions, 

 care should be taken to prevent contamination with urine of 

 objects or surfaces which are likely to come in contact with the 

 hands or other parts of the body of other people. As remarked 

 before, epidemics in mines are largely due to insanitary habits 

 and contamination of the ground. In mines or other places 

 where sanitary conditions are difficult to enforce, wholesale im- 

 munization would probably be effective, but good results can 

 also be obtained by disinfecting the ground. According to 



