1748 



Journal of Applied Microscopy 



Fig. 22. 



in their respective places and cover with the 

 bell jar. Introduce hydrogen through tube 

 (U). The air escapes in bubbles through 

 the glycerin in dish (D). In about ten 

 minutes open clamp (C), allowing the air in 

 wash bottle (F) to escape. After two more 

 minutes light the gas escaping at (C). If the 

 apparatus contains pure hydrogen the escaping 

 gas will burn with a quiet, even flame, other- 

 wise with a crackling noise. Being assured of 

 the complete replacement of air by hydrogen, 

 carefully withdraw the U tubes (U) and (F) 

 from the apparatus. In order not to disturb the glycerin seal by transportation, 

 Botkin recommends placing the apparatus in the incubator before hydrogen is 

 introduced. 



Hesse (1892) introduced the type of apparatus shown in Fig. 'I'l. It con- 

 sists of the following parts : 



a. A cast iron plate '20 cm. in diameter, with a channel (2 cm. wide and 3 

 cm. deep) at its periphery ; on one side the channel is 2^^ cm. deeper than at 

 the other. It is filled with mercury. The plate is smeared with shellac. 



b. A bell jar fitting into the channel and floating on the mercury. 



c. Two U tubes (c) and (c,), with extensions for the entrance and exit of gas 

 and air respectively. Tube (cj contains at (w) a wire gauze to ensure a safe test 

 of the escaping gas by burning. 



Method. — Cover the center part of plate (a) with a blotting paper for the pur- 

 pose of absorbing moisture. Upon this place the inoculated, loosely covered 

 plate cultures, invert the bell jar over them and insert the U tubes (c) and (c^) in 

 their proper places. Connect (c) with the Kipp generator. The purity of the 

 escaping gas is tested by applying a burning match to the capillary end of the 

 tube (cj. 



Baginsiky constructed an apparatus (Fig. 23) that appears to be simple in 

 construction and easy to manipulate. It consists of a large metal plate, the 

 circumference of which is covered with a thick rubber ring. A bell jar is inverted 

 over the plate and rests 

 on the layer of rubber. 

 Over the bell jar is placed 

 a metal plate similar to 

 that which forms the bot- 

 tom of the apparatus. 

 The bottom part contains 

 four projections in which 

 are hinged metal rods, the 

 outer ends of these rods 

 fit into similar projections 

 in the cover plate. By 

 means of these four metal Fig. 23. 



