The Procedure Adopted in the Plague Research Laboratory, Bombay, for Stoppering the Plague Prophylactic Bottles

Experiments on india-rubber and ordinary corks as to hoiu much time these take for sterilizing after immersion in Formalin lotion (2 p. c. strength). There are two sorts of the india-rubber ?corks, as supplied for the use of the Plague Research Laboratory. The one, that is the larger sized, is used for 30ccbottles. These are harder and tougher, and sit more easilj* on the bottles than the smaller variety (that supplied for 20ccbottles) which are soft and pliable. The specific gravity of the material used in making the larger corks is higher than the smaller ones. The latter float in water, while the former do not. This perhaps may be due to the proportion of sand, &c., used in their manufacture. The rule in the Laboratory is to dip the indiarubber corks three full days in formalin lotion (2 p. c. strength) before they are used. The formalin solution, it appears, has a tendency to more or less harden the substance of the corks, whether ordinary or india-rubber, besides making them sterile. A series of experiments were made in order to ascertain how much time formalin takes to sterilize the corks, both indiarubber and ordinary, and it has been found that three hours' complete immersion in formalin solution 2 p. c., for the india-rubber, and two days for the ordinary corks, renders them aseptic. For carrying out these experiments two dozens india-rubber corks and a dozen of ordinary corks were taken and tested in broth?inoculating two tubes (each containing about 20ccof broth) at every test, and the following results were obtained:?