480 
Combating Lousiness 
that it does not tarnish metal (buttons, etc.) on soiled clothing, that the 
clothing is always warm and dry when removed from the chamber and 
ready for immediate use 1 . 
Disinfestation by hot air should not take longer than with steam when 
the disinfestor works efficiently. If heated continuously (see Orr’s Hut, 
Model C, p. 447), a hot-air hut will perhaps be found in practice to act 
more rapidly than a steam hut, for the time occupied in the drying process 
and the manipulation of shaking the effects (on removal after steam 
disinfestation) must be reckoned to the total time required. 
On the other hand steam is greatly superior to hot air as ordinarily 
employed when it comes to disinfecting effects harbouring 'pathogenic 
bacteria. Stagnant hot air is inadequate for the purpose unless a high 
temperature is used, and this injures the articles exposed. Therefore, 
since steam accomplishes both the destruction of bacteria and lice it has 
the advantage of fulfilling a double purpose. The choice between dry or 
moist heat will therefore have to depend upon practical considerations 
in particular circumstances. 
It has been shown of recent years that current hot air is much more 
effective than stagnant hot air as a means of disinfection and there is 
reason to believe that in certain circumstances it may be used in place 
of steam. The earlier work of Koch and Wolffhugel (1881, Arb. a. d. 
Raised. Gesundheitsamte, i. 301) demonstrated that stagnant hot air at 
100° C. kills the vegetative forms of bacteria in 90 minutes, at 110-115° C. 
spores of moulds are destroyed in 90 minutes, whilst bacterial spores are 
only killed by an exposure for 3 hours at 140° C. This temperature 
injures fabrics, and, even after an exposure of 3-4 hours, bulky articles 
like clothes, bundles and pillows are not penetrated by the heat. This 
led to the general condemnation of hot air as a means of disinfection. 
When hot air circulates, however, the results are entirely different. Thus 
Schumburg (1902, p. 181) 2 , experimenting with a coffee-roaster, found 
that when it was rotated, spore-bearing bacteria enclosed therein in 
paper packets were mostly killed at 80-100° C. in 1 hour, whereas if they 
were not rotated whilst maintained at the same temperature, they sur¬ 
vived. This doubtless led to Vondran’s apparatus being evolved wherein 
1 The following rhyme, painted in large gothic letters along the beam of a German 
lousing establishment figured in an illustrated journal, although not scientific e'vidence, 
may indicate that the Germans prefer to destroy lice by dry heat: “ Holle, wo dieLause 
braten, ist der Himmel fur Soldaten” (Hell, where lice roast, is Heaven for soldiers). 
2 Schumburg (1902), Ueber die Desinfektionskraft der heissen Luft, Zeitschr.f. Hyg. xr.i. 
167-184. 
