96 HEISEU. 



As soon as proper health measures are put into effect to provide for 

 the disinfection of the stools of infected persons and the community 

 gradually acquires a temporary immunity, the outbreak slowly subsides, 

 and the disease does not again make its appearance in Manila until it is 

 either introduced from the outside or the cycle given above is repeated. 



It is conceivable that the immunity which has been referred to is due 

 to drinking city water, which at times contains a vibrio similar to that of 

 cholera but this does not appear probable. The outbreaks in the prov- 

 inces which are separated from Manila by open sea seem to be caused by 

 infected food, and this seems especially true if we consider the observa- 

 tion made by Dr. Cullen that the first persons attacked last yaer in 

 northern Samar all had eaten a poor quality of dried fish taken from 

 waters in Manila that were presumably infected. 



The fishing industry in and about Manila is conducted on a most 

 extensive scale. The low, marshy character of the section of the bay 

 north of the Pasig Eiver and the rise and fall of the tide, produce ideal 

 conditions for the growth and contamination of shell and other fish, 

 and this is especially accentuated since the tidal currents are such 

 that the contents of one of the city's largest sewers is extensively distrib- 

 uted throughout this area. Granting, then, for the sake of argument, 

 that fish, shellfish, and other sea products become infected with cholera 

 and that through imperfect cooking the organisms are not all killed, and 

 that one of the principal food substances of the masses in the city of Ma- 

 nila is gathered from the section just mentioned, it is evident that it would 

 be possible to immunize a large portion of the city's inhabitants. Enor- 

 mous quantities of sea products in a dry or partially dry state are also 

 sent to various portions of the Islands from Manila and if it should 

 happen that some of them have been shipped in a moist condition or are 

 otherwise rendered a good culture medium of cholera vibrio, it is 

 conceivable that such products might, in isolated instances, be the cause 

 of appearances of cholera in places such as Samar, Leyte, etc. In view of 

 the fact that this class of food products is the sustenance of the masses 

 because of its cheapness, it is more probable that the underfed members 

 of a community would be the first to be affected by the slight infection 

 which it might contain. 



In order to test the foregoing hypothesis, the Bureau of Science has 

 undertaken a laboratory study of the matter, and already investigations 

 made within the past few weeks of the sewers of the city of Manila 

 show that the cholera organism was present in them, and that almost 

 simultaneously with the disappearance of the disease in human beings, 

 about two weeks ago, it has been imjjossible to find any cholera vibrios in 

 these sewers. In view of the results of this study, it appears probable that 

 the cholera vibrio may live in the old Spanish sewers of the city of Manila 

 indefinitely. This fact may not be capable of demonstration the year 



