70 



CULTURES AND THEIR STUDY. 



which is plugged lightly with cotton so as to allow of plenty 

 of circulation of the air. One of the holes is meant to con- 

 tain a gas-regulating apparatus, which passes into the water 

 in the jacket. Any good regulator will answer the purpose 



FIG. 25. 



Showing certain macroscopic characteristics of colonies. (Abbott.) 



of regulating the temperature in the incubator. A thermom- 

 eter passes through the third hole into the inside of the incu- 

 bator. Incubating ovens are easily devised in case of neces- 

 sity. The vest pocket or watch pocket, or the axilla, or the 

 pocket of the night dress, will serve very nicely as an incu- 

 bator for cultures contained in small metal boxes or any con- 

 tainer which is not easily broken. For laboratory work, 

 however, an incubator is a necessity. 



