THE CULTIVATION OF MICRO-ORGANISMS 125 



Low-temperature Incubator.— An incubator regulated for so- 

 called "room temperature" is very desirable for the cultivation 

 of bacteria upon gelatin and for the bacteriological analysis 

 of water. In our climate the temperature of the rooms of the 

 laboratory often reaches a point at which gelatin melts, and 

 for this reason in a low-temperature incubator provision has to 

 be made for cooling when the room temperature is too high as 

 well as for heating when it is too low. 



A form of incubator devised by Rogers^ for this purpose 

 consists of a refrigerator or of a specially constructed chamber 

 heated by electricity and controlled by an electric thermoregu- 

 latbr. Below is given a description of an incubator constructed 

 according to Rogers' plans. This incubator has been in use 

 for some time and has given entire satisfaction since the precautions 

 noted below were followed. There would appear no reason 

 why this incubator should not be employed for high temperatures 

 as well as for low, but so far it has been run at 22° C. The tem- 

 perature has kept very constant. The incubator consists of a 

 refrigerator, 30 inches high, 24 inches wide, 18 inches from front 

 to back, all outside measurements. Instead of the ordinary 

 drip pipe, there is a coil of i-inch galvanized iron pipe run down 

 the back of the cooling chamber attached water-tight to the ice 

 tank. From the bottom of the cooling chamber the coil runs up 

 perpendicularly nearly to the bottom of the ice compartment, 

 and then runs horizontally through the wall of the refrigerator. 

 A bracket on the outside supports a drip-pan. A thermometer 

 encased in a fenestrated metal jacket is inserted 'about half 

 way up on one side. A lump of ice, about 50 pounds, placed in the 

 ice compartment serves to keep the temperature sufficiently 

 cool. In summer doubtless more ice will be required. 



For heating, an ordinary 16-candle-power electric bulb is 

 used, and the electricity is obtained from the pubUc supply. 

 The wire is run through one of the walls, and a part of the current 



'L. A. Rogers. On electrically controlled low temperature incubators. Cen- 

 tralblattfUr Bakteriologie, etc., Bd. XV, Abt. 11, pp. 236-239, Sept. 23, 1905. 



