CHAPTER IX. 



The incubator used in bacteriological work Gas-pressure regu- 

 lator Thermo-regulator The form of burner employed in heating 

 the incubator. 



THE INCUBATOR. When the plates have been made, 

 it must be borne in mind that for the development of 

 certain forms of bacteria a higher temperature is neces- 

 sary than for the growth of others. The pathogenic 

 or disease-producing organisms all grow more luxuri- 

 antly at the temperature of the human body (37.5 C.) 

 than at lower temperatures ; whereas, with the ordinary 

 saprophytic forms almost any temperature between 18 

 to 20 C. and that of the body is favorable. It there- 

 fore becomes necessary to provide some place in which 

 a constant temperature suitable to the growth of the 

 pathogenic organisms can be maintained. For this 

 purpose there have been devised a number of different 

 forms of apparatus. Fundamentally they are all based 

 upon the same principles, however, and a general de- 

 scription of the essential points involved in their con- 

 struction will be all that is needed here. 



This apparatus has the names thermostat, incubator, 

 and brooding oven. It is a copper chamber (Fig. 16) 

 with double walls, the space between which is filled with 

 water. The incubating chamber may be opened or closed 

 by a closely fitting double door, inside of which is usually 

 a false door of glass through which the contents of the 

 chambers may be inspected without actually opening it. 



