INCUBATION OF CULTURES 1 9 



turned on. After use it can be easily emptied by means of 

 the stop-cock at the side. It is specially adapted for opsonic 

 work or for testing the Wassermann reaction, and provision 

 is made for a tube of carbolic lotion, which will be found very 

 convenient for the Widal reaction by the pipette method. It 

 will answer every purpose the practitioner is likely to require, 

 unless he does an unusual amount of pathological work, and 

 its price is moderate. Foreign incubators can be obtained at 

 a lower price, but are not very durable. 



Much can be done without the use of so expensive an 

 apparatus if the practitioner can find a room in which the 

 temperature keeps approximately constant throughout the 



FIG. 6. INCUBATOR. 



twenty- four hours. A tin- biscuit box (or any other metal 

 box) is covered with cotton-wool on the top and sides, the 

 bottom being left bare, and mounted on a tripod stand. It is 

 heated by means of an ordinary night-light (two may be neces- 

 sary if the weather is cold) shielded from draughts by means 

 of a wide lamp-chimney or a tin cylinder made out of an 

 ordinary canister. The temperature is observed by means of 

 a thermometer projecting through a hole in the lid, and the 

 night-light raised or lowered until the temperature reaches 

 the desired figure. The whole apparatus should be' placed on 

 a metal tray containing a small quantity of water, and put in 

 the middle of the floor, and away from any inflammable 



