i6 



APPARATUS 



around the chamber containing the gelatin cultures. It requires some time for 

 proper adjustment, but afterward maintains a uniform temperature. Should the 

 temperature of the room in which the incubator is installed be below 22C. there is 

 provided an automatically controlled heating coil which operates when the surround- 

 ing temperature is lower than 22C. 



Centrifuge. When much serum reaction work is done, an electrically run centri- 

 fuge is an absolute necessity. It should be strongly constructed and placed on a 

 firm base. There should be places for 8 tubes and the outer shell or guard should 



FIG. 7. i, 2, 3, Drawing put glass tubing; 4, 5, Wright's rubber bulb capillary 

 pipettes showing grease pencil mark for making dilutions; 6, 7, Wright's U-tubes; 

 8, p, 10, methods of drawing out test-tubes for vaccines in opsonic workj'n, bac- 

 teriological pipette. 



be so strong that in event of the breaking of a tube, while the centrifuge is re- 

 volving at high speed, there would be no danger for the operator. Water-power- 

 driven centrifuges are less satisfactory and hand ones least so. 



An electric drying oven is very useful, taking the place of a water 

 bath. In reactions like that for blood acidosis, where the steam vapor 

 interferes, it is almost essential. 



Filter Pump. A filter pump attached to the water faucet, preferably by screw 

 threads, is almost indispensable for filtering cultures, etc., and for cleaning small 

 pipettes, especially the haemocytometer pipettes. Such a filter or vacuum pump with 



