Physiology. 473 
(15 ctm.) glass funnel is packed full with the dry sterilized cotton, 
placed in in layers, in such a way as to keep it well out of the neck, 
and having no folds nor ridges of cotton next the glass, through 
which the precipitates might pass into the receivin k. 
The neutralized culture medium, after being boiled with the 
white of egg, as above described, is strained through coarse flan- 
nel into a flask, and poured slowly upon the centre of the filter until 
the cotton is thoroughly soaked, and the fluid begins to run into the 
flask below. This moistening causes the cotton to sink consider- 
ably, and packs it in the funnel, and when packed, the fluid filters 
through it almost as rapidly as it is poured into the funnel. The 
funnel is now filled and the fluid filtered as fastas it will run 
through. The first filtration seldom produces a clear medium, but 
through the same filter the fluid may be poured again and again, 
each time becoming clearer, and the moderate cooling which neces- 
sarily occurs, does not sensibly retard the rapidity of filtration. 
When filtration is completed, a considerable portion of thè medium 
entangled in the filter can be saved, by pressing upon the cotton 
with a sterilized glass rod, gently at first and near the sides, then 
in the centre and with considerable force. The gelatine or agar 
pressed from the cotton is sometimes cloudy, for which reason it is 
well to catch it in a separate flask. 
_ It not infrequently happens that gelatine which filters clear pre- 
Cipitates phosphates on boiling; and that agar, on cooling, forms a 
occulent precipitate. To insure against filling tubes with such 
media, it is safest always to fill one tube with the medium, and by 
first cooling, then by boiling and again cooling, to test the perma- 
nence of the transparency obtained. Should these precipitates form, 
it will be necessary to boil the gelatine in the flask, and to refilter 
it through a small plug of dry cotton placed in a funnel; while 
agar should be allowed to completely solidify, when it is again 
melted and filtered through a small plug of cotton, The media are 
now ready for tubing and sterilizing in the usual way. 
he large quantity of absorbent cotton used and the considerable 
amount of medium lost, by remaining entangled in the meshes o 
the cotton (this may amount to 200 c. ¢. for each of the large cotton 
filters employed) are unquestionably objections to this method of 
filtration, but in its favor it may be stated that one filter when 
properly packed, serves to clear a large quantity of medium, and 
the great saving of time in filtering, enables one to prepare a large 
amount of these nutrients at one operation, which may be stored 
or future use. Futhermore, the “ hot funnel ” is dispensed with. 
The modifications here described may be best appreciated by — 
the fact that they render it possible to prepare within three hours 
Several litres of the above-mentioned culture media.—T. M. Chees- 
man, Jr., M.D. (From the Bacterial Laboratory of Alumni As- 
cn) of the College of Physicians and Surgeons, New York- 
