114 TEXT-BOOK OF BACTERIOLOGY. 



The best way of proceeding is as follows. Take a number of 

 gelatin test-tubes, inoculate, and make the necessary dilutions, etc., 

 as usual, and then, instead of using a cotton plug, close each tube 

 with a gutta-percha stopper, which should be previously sberilized 

 in the steam generator, and whose two holes contain two glass 

 tubes bent to a right angle. The longer of the two reaches down 

 almost to the bottom of the test-tube, deep into the food medium ; 

 the other is cut off close below the stopper. In both the horizontal 

 part is contracted into a narrow neck; the continuation of the 

 longer tube contains, further, a pledget of sterilized cotton wool, 

 and ends in a short piece of India-rubber tubing. By means of this, 

 while the gelatin is still in a liquid state, we connect the test-tube 

 with Kipp's apparatus and let the stream of gas enter. It drives 

 out the air from the food medium and test-tube, which escapes by 

 the shorter of the two glass tubes. After about half an hour melt 

 and seal up, first, the short, and afterward the long tubes, and lastly, 

 roll the gelatin over the walls of the test-tube. 



This process may often be employed with success, and besides 

 its other advantages, its simplicity and cheapness distinguish it 

 favorably from another method which is, nevertheless, often em- 

 ployed, and must therefore be mentioned here. It is the method of 

 Liborius, to whom also, as known, we chiefly owe the culture system 

 in deep strata. Liborius also conducts a stream of hydrogen 

 through the inoculated food medium, but he employs special appa- 

 ratus for doing so. He uses small glasses, to the side of which a 

 tube is firmly attached by melting. This tube is continued down- 

 ward within the test-tube almost to the bottom. When the stream 

 of gas passes through this tube it must first pass through the food 

 medium before it can escape through the mouth of the test-tube, 

 which has been contracted to a narrow neck. When the air has been 

 carefully expelled, first the feeding-pipe and then the neck are 

 melted and sealed up, the food medium remaining under an atmo- 

 sphere of pure hydrogen. 



It must be regarded as a disadvantage of this method that the 

 colonies, as in the deep-stratum culture, can hardly be examined 

 direct with the microscope, and can only be approached with diffi- 

 culty for the purpose of further inoculations. It is also a disad- 

 vantage that we do not here roll out the food medium on the walls 

 of the test-tube. 



When we have attained, in either of the already-described ways, 

 a distribution of germs, and have developed colonies of anaerobic 

 bacteria so that they are ready for further treatment, proceed as 

 in the usual breeding process to needle-point cultures. To this end I 

 recommend the exclusive use of deep strata of solid food media. 



