20 



CLINICAL BACTERIOLOGY AND HEMATOLOGY 



have to be incubated, the water-jacket must be filled with water 

 at body heat and the gas or lamp lit, or, in the case of an electric 

 apparatus, the current turned on. After use it can be easi y 

 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. 



Fig. 10. — Incubator. 



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 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 necessary 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-hght raised or lowered until the temperature reaches 

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



