132 



BACTERIOLOGY. 



In the method recommended by Frankel a tube of gelatine is 

 Hquefied, and inoculated. A gutta-percha stopper is substituted 

 for the cotton-wool plug (Fig. 66). It is perforated by two holes, 

 through which two tabes pass which are bent at a right angle. 

 One tube only just passes through the stopper, the other reaches 

 down to the bottom of the test-tube. The 

 horizontal part of each tube has a narrow 

 neck. The long tube has a plug of steril- 

 ised cotton-wool, and is connected with 

 a short piece of india-rubber tubing by 

 which it can be connected with Kipp's 

 apparatus. The hydrogen di'ives the air 

 out of the liqviefied jellj^ and out of the 

 test-tube, and after about half an hour ■ 

 the horizontal tubes are sealed up, and 

 the test-tube is made into a roll culture. 



Liborius employs a tube with a narrow 

 neck and a lateral arm (Fig. 67). The 

 tube is filled up to the height of the arm 

 with either nutrient agar or a mixture of 

 nutrient agar with 2 per cent, of grape- 

 sugar. The hquefied jelly is inoculated 

 in the usual way, and hydrogen passed 

 through the lateral arm. When the air 

 has been completely driven out, the tube 

 is sealed up. 



To cultivate anaerobic organisms in 

 broth, such as the tetanus bacillus, a flask 

 is inoculated with the bacillus, and a 

 stream of hydrogen is passed through the 

 broth by means of a tube passing down to the bottom of the 

 flask. The air in the flask escapes by a lateral arm which is bent 

 ■down at a right angle, and immersed in a capsule of mercury. 

 When the air has been completely expelled the entrance tube is 

 hermetically sealed, and the mercury in the capsule prevents any 

 air from re-entering the flask by the lateral arm (Fig. 68). 



Fig. 67. — Anaeeobic Cul- 



TUEE-TUBE (LiBOEIUS). 



Method of Fixing Cultures. 



The colonies in plate-cultivations and the growths of bacteria 

 in test-tubes may be stopped at any stage of their growth, and 

 permanently fixed by exposing the culture to the fumes of formic 



