63 
be placed under. The top or lid {<■) was made 8 inches high, of the 
same diameter as tlie lower portion, fitting into it tightly, so as to 
avoid the escape of steam and decrease of pressure as much as pos 
sible. Tli rough the center of this cover was fitted a collar (d) in the 
shape of an inverted cone, about '■> inches long. I inches in the larger 
and 2J in the smaller diameters. Fortius collar a tight fitting lid like 
that for a tin pail was provided, in order that the same top might be 
l'scd either for hot filtering or simply for sterilizing. To one side of 
the funnel collar, in the top of the lid a second small collar was fitted. 
for the reception of a thermometer. On the side a slender, slightly bent 
handle for lifting the top off and on was placed. 
When any hot filtering- is to be done, the flask containing the me- 
dium is placed in the sterilizer and brought to a boil. At the same 
time a second empty flask is put in on the diaphragm. The top is then 
placed on. The funnel is provided with the necessary filter paper and 
the whole inserted through the collar (d) in the top of the sterilizer. 
The steam arouud the funnel keeps it hot and that escaping through 
the neck moistens the filter paper. When the liquid to be filtered 
reaches the boiling point, the flask containing it is taken out. the hot 
funnel at once fitted through the collar, into the empty flask, inside 
the sterilizer. The liquid is then poured into the funnel and the filter- 
ing proceeds without further interruption or special care. The body 
of the funnel being inside the sterilizer the steam has full play upon 
it. keeping it and the liquid almost at boiling during the entire process. 
At the same time other flasks containing media can be placed in and 
sterilized while the filtering goes on. The flask receiving the filtrate 
being in the sterilizer, any danger of falling germs or spores in the air 
settling upon the liquid is avoided. 
The funnel collar should not extend more than a half inch above the 
level of the top, so as to -allow almost the whole of the funnel to be 
inside the sterilizer. 
For some media the pressure of the steam through the funnel checks 
the rapidity of the filtering. To avoid this a ruffled collar, instead of 
a perfectly circular one, can be made, thus allowing the escape of steam 
and relieving the internal pressure. The lid to the collar must be made 
to fit accordingly. If desirable a plain top(D) can be made for ordinary 
use in sterilizing, in which case the lid to the funnel collar in the other 
is not necessary. The respective dimensions must of course be adapted 
by each maker to his particular purpose. To prevent the radiation of 
heat as much as possible, the sterilizer is covered or bound in the usual 
manner with asbestos (g). 
Another piece of apparatus, which may be called an ••incubating 
cage," Fig. F. was also devised which in many respects materially 
facilitates work. The cages in which culture tubes are usually placed 
when transferred to the incubator are the well known wire cages, hold 
ing some twenty or thirty tubes. This entails a great inconvenience 
