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 disinfected. 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. [Illustration: ANIMAL HOUSE] It will be noticed that the epidemic lasted eleven days after the first animal died and fourteen days after animal 1 was inoculated. 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 surrounded by plague guinea-pigs 8, 9, and 10, 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 centimetres high, the rest of the animals were kept in regular metal animal cages. The dimensions of the cages are: Fifty centimetres long, 36 centimetres broad, and 30 centimetres high. The cage stands on four legs each 10 centimetres long; the centre of the bottom of the cage holds a drain opening 8 centimetres 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 centimetres high. Only a theoretical explanation can be given of the short duration and sudden cessation of the outbreak. One can assume with great probability that the first partial disinfection drove the fleas away from the primary source of infection, and that they traveled as far as possible. They finally settled in those guinea-pig cages which had not been molested by the first disinfection. Having no new supply of plague blood (all of the plague-infected guinea-pigs having been removed, most of them before death), the fleas soon cleared themselves of plague bacilli. The peculiar feature of the outbreak, namely, the failure to find fleas on the animals in rooms II and V, finds its explanation in the observation of the Indian Commission who found that the fleas "died or disappeared very rapidly."