POWERS OF RESISTANCE. 383 



anaerobic organisms, such as those of tetanus and malignant 

 oedema, though it occurs more slowly than in the presence 

 of oxygen. In the intestines the oxygen supply, though small 

 in amount, is yet sufficient for the growth of the spirilla. 



Powers of Resistance. In their resistance against heat 

 cholera spirilla correspond with spore-free organisms, and 

 are killed in an hour by a temperature of 55 C, and much 

 more rapidly at higher temperatures. They have com- 

 paratively high powers of resistance against great cold, and 

 have been found alive after being exposed for several hours 

 to a temperature of - 10 C. They are, however, killed by 

 being kept in ice for a few days. Against the ordinary 

 antiseptics they have comparatively low powers of resistance, 

 and Pfuhl found that the addition of lime, in the proportion 

 of i per cent, to water containing the cholera organisms, was 

 sufficient to kill them in the course of an hour. 



As regards the powers of resistance in ordinary ' cpr^ 

 ditions, the following facts may be stated. In cholera 

 stools kept at the ordinary room temperature, th\^ cholera 

 organisms are rapidly outgrown by putrefactive bacteria, but 

 in some cases they have been found alive even after two or 



J 



three months. In most experiments, however, attempts tcNsi-^ 

 cultivate them after a much shorter time have failed. The 

 general conclusion may be drawn from the work of various 

 observers that the spirilla do not multiply freely in ordinary 

 sewage water, but that in certain circumstances they may 

 live for a considerable period of time. In distilled water 

 they remain alive for several weeks at least, but do not 

 multiply, nor does any considerable growth take place 

 without the presence of a pretty large proportion of organic 

 matter. On moist linen, as Koch showed, they can flourish 

 very rapidly. When the cholera organisms are grown along 

 with other organisms in fluids at a warm temperature, it is 

 found that at first they may multiply more rapidly than the 

 others, but after a certain time they are outgrown by some 

 of the organisms present, gradually diminish in number, and 

 ultimately disappear. It must not, however, be inferred 

 from such experiments that a similar result will necessarily 



