Four cases under one roof on Calle San Fernando (November 12, 13, 16 and 22); 2 cases in one house on Calle Teodoro Alonzo (November 26 and December 2); and 2 cases in the same house on Calle Cabildo (Intramuros), November 23 and December 11. These multiple cases will be referred to elsewhere. The other cases during October, November and December were apparently sporadic and unrelated, either to the other human cases or to the few scattering cases of rat plague discovered from time to time. Without doubt, however, all were actually related to preceding cases of rat plague, _i.e._, to undiscovered rat cadavers, dead from plague and deserted by infected fleas. In the following plague houses (see list of cases) dead rats were actually found, although the advanced degree of desiccation and mummification defeated the biologic determination of the cause of death: 518 Calle Teodoro Alonzo; 973 Calle Azcarraga; 282 Estero de Binondo. In other plague houses the recent finding of dead rats was alleged by the occupants, but rather too indefinitely to record positively. A study of the maps and lists showing the localities in which cases of rat plague had been found up to this time (December 26, 1912), in connection with the location of plague houses, was much less suggestive than a similar study of the lists and maps covering the cases of 1913. However, the existence of concurrent rat plague and human plague, in corresponding sections of Manila, had been well established already by bacteriologic studies of captured rats, made at the Bureau of Science. Of nearly equal weight was the observation concerning the two epidemics, rat and human, at the Railway Station, which I have already described. The year 1912 closed, then, with a recorded total of 50 human cases and 7 verified cases of rat plague. January, 1913, saw but a single case of human plague. This occurred on January 24, just a month from the last previous case, that of Christmas Day. During this month no case of rat plague was reported. In February, 3 human cases occurred and in March, 4 cases were recorded. Early in March, 1913, cases of rat plague began to occur in the Tondo district in a section lying between Manila Bay and the Estero de la Reina and extending northward from Calle Moriones. This was a new district for rat plague and as the cases increased in number we were able to foresee and predict the appearance of human plague in the same district, which in point of congestion of population, poverty of its residents and in the matter of dilapidation of its light material houses and shacks, is about the worst locality in Manila. From March 22 to September 20, 1913, all the cases of human plague, 11 in number, occurred in the midst of this district. During the same period 25 cases of rat plague were reported from the same section, and a glance at a map of this part of Tondo instantly shows the relationship existing here between rat plague and human plague.