66 CULTURES IN LIQUID MEDIA. 
berg’s bulbs,” as they are sometimes called, are that a culture me- 
dium may be preserved in them indefinitely and that they are easily 
transported from place to place; whereas test tubes, Pasteur’s flasks, 
and similar receptacles must be kept upright, and after a time the 
culture liquid in them is changed in its composition by evaporation. 
They are also liable to be contaminated by the entrance of mould 
fungi when kept in a damp place. The spores of these fungi, falling 
upon the surface of the cotton air filter, germinate, and the myce- 
lium grows down through the cotton into the interior of the tube, 
where a new crop of spores is quickly formed. It is, therefore, a 
convenience to have sterile culture liquids always ready for use in 
a receptacle which can be packed in a box and transported from 
place to place ; but for every-day use in the laboratory the ordinary 
test tube, with its cotton air filter, is the most economical and conve- 
nient receptacle for culture liquids as well as for solid media. With 
reference to the method of making and using these little flasks, I 
quote from a paper published in the American Journal of the 
Medical Sciences in 1883 :' 
The culture flasks employed contain from one to four fluidrachms. 
They are made from glass tubing of three- or four tenths inch diameter, and 
those which the writer has used in his numerous experiments have all been 
‘‘home-made.” It is easier to make new flasks than to clean old ones, and 
they are thrown away after being once used. Bellows operated by foot, and 
a flame of considerable size—gas is preferable—will be required by one who 
proposes to construct these little flasks for himself.’ After a little practice 
they are made rapidly; but as a large number are required, the time and 
labor expended in their preparation are no slight matter. After blowing a 
bulb at the extremity of a long glass tube, of the diameter mentioned, this 
is provided with a slender neck, drawn out in the flame, and the end of this 
1««The Germicide Value of Certain Therapeutic Agents,” op. cit., vol. clxx. 
? A glass-blower ought to make them for two or three dollars per hundred. 
