58 



MICROBIOLOGY 



as in a student laboratory is very convenient. For heating- 

 incubators, gas burners are usually employed and those with 

 an automatic cut off or safety burners are most desirable.. 

 The temperature of the incubator is regulated by means 



Fig. 22. Wright's device. The apparatus 

 consists of a system of glass and rubber tubes 

 standing in an ordinary test tube. (A), is a 

 glass tube somewhat constricted at each endr 

 (B), (C), and (E) are short pieces of rubber tub- 

 ing; glass tube (D) carries in its upper extrem- 

 ity a small cotton plug. The test tube contains- 

 some culture fluid as indicated in 1. 



QQO 



-I- -2.- 



Fig. 22. Fig. 23. 



Fig. 23. Baginisky's apparatus. 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 bottom 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 rods the upper and the lower metal plates are 

 tightly pressed against the bell jar, closing the apparatus hermeti- 

 cally. On opposite sides the. bell jar contains small lateral tubes by 

 means of which hydrogen is introduced and air driven out. 



of a thermostat. There are many varieties of thermoregu- 

 lators; some are controlled by the use of alcohol and ether, 

 others by mercury and still others use a metallic bar the 

 contraction and expansion of which controls the flow of gas. 



