420 ' The Philippine Journal of Science 1913 



Guinea pigs 3, 4, and 5 (see plan) were found dead on the 

 morning of September 2; that is, two days after the death of 

 rat 2 and three days after the death of rat 1. 



The same day that the three guinea pigs were found dead 

 of plague, rooms I, III, IV, and VI (see plan) were thoroughly 

 disinfected. The floor, the ceiling, and the walls were sprayed 

 with kerosene and lysol solution. The remaining animals in 

 room VI were destroyed, and the cages disinfected. No animals 

 were kept in rooms I, III, and IV at that time. 



Three days after the death of animal 5, guinea pigs 6 and 7 

 were found dead of plague, while the next day guinea pigs 8 

 and 9 died. No death occurred on September 7, but the next 

 two days each recorded two plague guinea pigs (10, 11, 12, and 

 13). On September 11, the last guinea pig died of plague in 

 this outbreak. The whole building was then thoroughly dis- 

 infected. No plague-inoculated animals were kept in the rooms 

 after the first sign of the epidemic. After September 11, no 

 more cases of spontaneous plague infection were observed. 



It will be noticed that the epidemic lasted eleven days after 

 the first animal died and fourteen days after animal 1 was in- 

 oculated. Altogether, 14 animals out of at least 200 animals 

 exposed died of plague. 



No death occurred among rabbits, although these animals were 

 distributed among the guinea pigs. In fact, 2 rabbits were sur- 

 rounded by plague guinea pigs 8, 9, and 10 (see plan), but did 

 not contract plague. 



From the epidemiological standpoint it is interesting to know 

 the dimensions and location of the cages in which the animals 

 were kept. 



Aside from the 2 rats which were confined in ordinary 

 traps that stood on a table 80 centimeters high, the rest of the 

 animals were kept in regular metal animal cages. The dimen- 

 sions of the cages are: Fifty centimeters long, 36 centimeters 

 broad, and 30 centimeters high. The cage stands on four legs 

 each 10 centimeters long; the center of the bottom of the cage 

 holds a drain opening 8 centimeters above the floor. 



The majority of the cages in room II were located on the 

 floor; some on the second shelf of a wooden rack. This last- 

 mentioned arrangement, judging from the construction of the 

 wooden frame, allowed a continuous passageway for the fleas 

 to the second shelf of the racks. On the other hand, the deaths 

 among the guinea pigs in room V were restricted to the cages 

 standing on the floor, the majority of cages in that room being 

 placed on tables 80 centimeters high. 



