ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
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sterilized, and several may be sterilized at once by placing them in a 
tin box with a number of shelves (fig. 93). 
Fig. 93. 
TL 
Fig. 92. 
Air Filter.* — Herr J. J. van Hest describes at considerable length a 
simple apparatus which he has devised for filtering air and thus freeing 
it from bacteria, fungi, &c. The principle of the filter depends on the 
fact that thesejorganisms are not devoid of weight, and hence if a current 
Fig. 94. 
of air be passed through a fine tube with a perfectly smooth interior and 
numerous coils or turns in its circuit, organisms will be deposited inside. 
The rapidity with which the air may be driven through is 1 * 5—2 m. 
* Centralbl. f. Bakteriol. u. Parasitenk., xvi. (1894) pp. 435-47,495-99(11 figs.). 
