6G 



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 



FIG. 37, 



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.' 2 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. 

 8 A glass-blower ought to make them for two or three dollars per hundred. 



