THE INCUBATOB AND ACCESSOEIBS. 251 



inches in diameter. By means of the gas-pressure and tem- 

 perature regulators, which have been described, it is pos- 

 sible to maintain a constant warmth even if the incubator 

 is placed in a room where the ambient temperature is liable 

 to considerable variation. 



Micro-burners. — The outflow tube of the thermo- 

 regulator should be connected with a suitable burner placed 

 underneath the incubator. An ordinary Bunsen burner may 

 be used in some instances, but, as a rule, it gives off too 

 much heat, and, moreover, the flame 

 is' liable to "shoot back" when the 

 supply of gas is low. A very good 

 micro-burner can be obtained by un- 

 screwing the tube of the Bunsen 

 burner. The gas now burns with a 

 luminous flame, but this does not in- 

 terfere with its usefulness. A cyl- 

 inder of copper wire-gauze may be 

 placed around the flame to prevent 

 currents of air from extinguishing it. 



The small narrow Bunsen burner, 

 so-called microburner, can be used to 



, , . T , , , J , T Fig. 39. Koch's safety burner, 



better, advantage than the ordinary a— Metal spiral, one on each side 



■ T. . . T . . of flame; d — Arm moved by the 



form. Small iet, luminous micro- spirals; «— Weighted lever arm 



of stop-cock, supported by ^. 



burners can also be used, but they 



possess no advantage over that obtained in the manner 



described above. 



The lamp usually employed under an incubator is 

 known as the safety burner. This is intended to shut off the 

 flow of gas, if for any reason the light should go out. The 

 gas is thus prevented from escaping into the room, and 

 danger of subsequent explosion is thus avoided. Several 

 forms of the safety burner have been devised, but the one 

 which is used perhaps the most often is that of Koch. 

 Obviously, the safest procedure is to place the incubator, or 



