3IO BACTERIA. 



and Roux and Yersin have found that the specific bacterium 

 may persist in the mouth for several days (in one case four- 

 teen days) after all traces of the membrane have disappeared, 

 and they give the good practical advice that diphtheritic 

 patients who are becoming convalescent should not be 

 allowed to associate with their school-fellows, play-mates or 

 families, for at least a fortnight after the membrane has 

 disappeared ; and that it is quite as important to wash out 

 the throat freely three or four times a day with disinfecting 

 lotions as that the clothes and bed linen should be 

 thoroughly disinfected. As regards the tenacity of life 

 exhibited by these bacilli, it is found that at the ordinary 

 temperature of the room these organisms retain their 

 vitality for a period of at least six months, and pro- 

 bably considerably longer. As the temperature rises this 

 period is gradually diminished, for we find that at 33° C. 

 the organisms succumb in about five months ; whilst at 

 39° C. they are are found to be no longer capable of living 

 and of multiplying when introduced into solidified blood 

 serum or glycerine-agar. When deprived of air and pro- 

 tected from the light, even when kept at the ordinary 

 temperature, they may continue capable of germinating, 

 when introduced on to a suitable soil, for a period of 

 thirteen months. If they are dried and are kept at the 

 temperature of the room, they are killed in four months, at a 

 temperature of 33° C. they are killed in three months, and 

 at a temperature of 45° C. in four days. If a fragment of 

 the false membrane containing bacilli be removed, wrapped 

 in sterilized paper, or linen, and be carefully protected from 

 the action of light, cultivations may be made from it at any 

 time during a period of five months. If,- however, instead of 

 keeping it dry and in the dark, fragments of these mem- 

 branes are exposed to the light and moistened and desiccated 

 alternately, the virus is destroyed much more rapidly. From 

 all this, and from the fact that the bacillus is destroyed by 

 moist heat at 58° C, it is evident that by far the best method 

 of disinfecting clothes, the floor, the walls, and furniture, is 

 by the use of a liberal supply of boiling water ; for although 

 a temperature of 98° C. (dry), continued for an hour is 

 necessary to destroy the vitality of the bacillus, moist heat 

 at a very much lower degree (acting only for a minute 

 or two, according to the temperature) is sufficient to dis- 



