io 4 METHODS OF STERILISATION. 



the boiling water. This is, of course, dependent on the prevail- 

 ing atmospheric pressure, and generally ranges between 96 and 

 1 00 C. A reduction of the time of exposure is not to be thought 

 of, since here, as before, we have to do with a temperature of only 

 about 100; this must be particularly emphasised, since the Koch 

 school at one time fell into error on this point, by promulgating 

 the maxim that " the spores of bacilli cannot withstand the 

 temperature of boiling water for more than a few minutes." We 

 have already recalled a fact controverting this, and will now cite 

 a second example, given by GLOBIG (II.), viz., that the endospores 

 of a species of bacterium, discovered by this observer on potatoes, 

 originating therefore in cultivated soil, and named the "potato 

 bacillus," resisted the influence of a current of steam at 100 C. 

 for as much as six hours. This is the most powerfully resistant 

 of all organisms hitherto observed. 



Numerous modifications have been made in Koch's steriliser, 

 in accordance with the special purposes for which it is intended. 

 Thus, for example, the water-chamber has been separated from 

 the steam-chamber, and the steam introduced into the latter from 

 above. This pattern is specially preferred in the case of the large 

 apparatus employed for disinfecting invalids' linen, hospital bed- 

 ding, and the like. Readers desirous of obtaining full information 

 on this point are referred to a treatise by DUNCKER (I.), who sub- 

 jected a number of steam-disinfectors to a careful examination. 

 The simple and inexpensive form described above is sufficient for 

 the purposes of the fermentation physiologist. 



In the fermentation industries the method of destroying germs 

 by steam is highly prized on account of its convenience and efficacy. 

 In breweries, for instance, all the piping is steamed out, as also 

 the wort cooler, and so on. The Enzinger filter, however, cannot 

 be treated in this way, owing to the softening action of moist heat 

 on the filter paper. 



The duration of exposure requisite for the destruction of 

 germs by moist heat can be considerably shortened by employing 

 supersaturated high-pressure steam. If, for example, the steam be 

 used at a temperature of 120 C. (corresponding to an extra-pres- 

 sure of one atmosphere), an exposure of twenty minutes suffices 

 for sterilising liquids up to 50 c.c. in volume with certainty. For 

 larger quantities a corresponding additional exposure at 120 C. 

 (five to ten minutes) is given. The use of supersaturated high- 

 pressure steam is attended with much smaller outlay, but requires 

 a strongly built autoclave. Laboratories already possessing such 

 an apparatus which is required, for example, in the determina- 

 tion of starch in cereals, &c. can also employ it to advantage for 

 sterilising. In many instances, too, a method of this kind is 

 advisable, not only on account of the saving in fuel, but also by 

 reason of the fact that the chemical composition and nutritive 

 quality of the liquid to be sterilised are less impaired by fifteen 



