n6 METHODS OF STERILISATION. 



and i c.m. wide) is placed over the slightly projecting lighted 

 wick, and as soon as the gauze is red hot the flame is extinguished r 

 whereupon the formation of formaldehyde goes on uninterruptedly. 

 It should not be forgotten that as pointed out by A. BROCKET (1.) 

 this incomplete combustion of methyl alcohol also produces 

 some 3 to 5 per cent, of carbon monoxide. An apparatus con- 

 structed by Krell, and resembling the Barthel soldering-lamp, has 

 been described by A. DIEUDONNE (II.), by means of which a 

 constant current of formaldehyde vapour can be produced from 

 methyl alcohol and blown into crannies and corners that require 

 disinfecting. The different degree of susceptibility exhibited by 

 the various bacteria towards this poison has been utilised by E. 

 SCHILD (I. and II.) for the differentiation of typhus bacilli from 

 the very similar Bacterium coli commune, which, in the bacterio- 

 logical analysis of water, is both very important and difficult. 

 The latter species develops freely in a bouillon containing i part 

 of formaldehyde in 7000, whereas the former will not do so. 

 Therefore, if a species of fission fungus isolated from the sample 

 of water, and suspected to be typhus bacillus, produces turbidity 

 in such a medium, this behaviour shows that it is not the bacillus 

 which causes typhus. The applicability of this method which gives 

 a negative characterisation has been confirmed by RUD. ABEL (I.) rf 

 The researches above noticed deal only with the action of formal- 

 dehyde on bacteria, but for the fermentation industry it is also 

 important to know how the higher fungi, and especially the alcohol 

 yeasts, behave towards this disinfectant. In this connection it has 

 been established by W. WINDISCH (I.) that yeast cells show much 

 less susceptibility ; consequently this aldehyde is not a suitable 

 means for killing them. Fortunately, however, they are readily 

 affected by the influence of hot water vapour, chloride of lime, &c., 

 so that there is no lack of available remedies. 



The antiseptic power of iodoform, CI 3 H, was studied by 

 BEHRING (I.), with the result that this compound was found not 

 to injure (kill) bacteria, except in the rare cases when iodine was 

 liberated. In all other instances (which thus constitute the rule), 

 its favourable action in the healing of wounds is based exclusively 

 on the counteraction of the poison produced by the pus-forming 

 bacteria, without, however, the appearance of the latter being 

 prevented. The use of chloroform for disinfection is only, as a 

 rule, resorted to when it is desired to sterilise milk for use as a 

 culture medium, in which case it is necessary to dispense with 

 strong heat. This will be discussed in a subsequent chapter. 



The organic acids have a fatal effect, even in small quantities, 

 especially on putrefactive bacteria. Frequent and regular use is 

 made of this property in technical processes of sterilisation, as 

 also in distillery work ("souring the mash"), as will be frequently 

 noticed in the course of the present work. On the other hand, 

 fairly high degrees of concentration are required for killing such 



