112 The Philippine Journal of Science i9i8 



nation proved positive for plague. The next case of plague did 

 not occur until August 4 — thirty-nine days later. This victim 

 of the disease resided at 139 Calle Villalobos, in Quiapo, The 

 case was followed by another, on August 8, at 129 Calle Villa- 

 lobos (five houses removed from the former case), and by a 

 third case, on August 21, at 352 Calle Echague. This address 

 is just around the corner from where the Calle Villalobos cases 

 resided. A noteworthy fact in connection with these three cases 

 is that all were schoolboys, the oldest being 16 years of age. 

 The disease then occurred at irregular intervals, there being 

 but 3 cases in September, and, during October, to the 20th, there 

 were 4 cases, all of which occurred on diiferent streets, as may 

 be seen from the accompanying map, the total of all cases to 

 that date being 13. Then, between the dates of October 20 

 and October 22, 13 new cases occurred, so that, in a period of 

 two days, there were as many cases as there had been during 

 the four previous months. 



EXPLOSIVE HUMAN OUTBREAK 



An investigation of the large number of cases that occurred 

 within the two days mentioned soon showed that they were all 

 confined to laborers who worked at the Manila and Dagupan 

 Railroad freight station. Large numbers of rats had been seen 

 dying in, first, the north warehouse, and, a few weeks later, 

 in the south warehouse. About three weeks after the heavy 

 rat mortality was noticed in the north warehouse, plague ap- 

 peared among the laborers in the south warehouse. It is 

 believed reasonable to infer that the large number of cases of 

 plague among these laborers is due to the fact that as the rat 

 mortality was rapidly eliminating the normal supply of nourish- 

 ment for the fleas, the latter began to attack human beings. 

 This outbreak was brought to a speedy close by eradicating the 

 rats and sprinkling the premises with kerosene to kill the fleas. 

 The total number of cases in Manila, to November 5, was 33, 

 and of these 30 died. 



PLAGUE AMONG RATS 



As soon as the first case of plague was discovered among 

 human beings, an active rat-catching campaign was begun, 

 efforts being concentrated to the vicinities in which human cases 

 had occurred. Rats were caught at the rate of approximately 

 3,000 per month, but it was not until August 31 that a plague 

 rat was found. This was caught in a spring trap at 351 



