192 The Philippine Journal of Science 1915 
According to the resident physician, Dr. José Marfori, the 
admissions during this period somewhat exceeded the average. 
It is impossible to state what portion of these 25 cases are re- 
currences. But all prisoners had spent at least two years in 
Bilibid Prison at Manila before coming to Iwahig. We have 
received the following information from the Bureau of Health: 
Malaria is infrequent among prisoners who have been in Bilibid for 
two years or more. Occasionally malaria develops, apparently from latent 
infection, after operation. During the month of December, 9 tubercular 
patients were returned from Iwahig, among whom 4 were found with the 
enlarged spleens and blood positive for malarial organisms. 
So it is likely that malaria in a large proportion of the cases 
mentioned in Table IV was contracted in Iwahig. 
With regard to the amount of latent malaria at Iwahig we 
have data of 62 men of the central brigade dormitory, the 
occupants of which are probably somewhat less exposed to in- 
fection than the average population. Only men apparently 
healthy were examined. Of the 62, 8, or 12.9 per cent, harbored 
malaria parasites. Of the 8 positives the length of residence in 
the colony was as follows: Three months, 1 person; eight months, 
1; nine months, 1; eleven months, 2; one year, 1; three years, 2. 
A noteworthy deduction from the data obtained at Iwahig is 
the large proportion of A. febrifer as compared with other species 
of anopheles, and the large number of A. febrifer found in houses 
in proportion to the number of larve found in the neighboring 
breeding places. Further, it seems to be demonstrated that the 
flight of this species is at least 170 paces, although comparatively 
few got so far. 
The data from both Iwahig and San Jose, Mindoro, demonstrate 
that Anopheles febrifer, like A. rossii, is a house-seeking species 
and readily takes blood from human beings. In both San Jose 
and Iwahig A. barbirostris was found in dwellings, and the fact 
that specimens of A. barbirostris containing blood were found 
in sleeping nets at Iwahig proves that this species will enter 
houses and bite human beings. In India A. barbirostris has 
been generally considered a “wild” species, little disposed to visit 
houses.° When we compare the small number of this species 
found in nets in Iwahig with the number of larve found breeding 
in the vicinity, it seems probable that in the Philippines, also, this 
species has a less tendency to visit houses than either A. febrifer 
or A. ross. Only one specimen of A. maculatus was found in 
‘Stephens and Christophers, The practical study of malaria, ete. The 
University Press of Liverpool (1908), 169, 181. 
