INCUBATION 241 



The fact that, in natural incubation, eggs seem to hatch equally 

 well under very different atmospheric conditions indicates that as 

 close adjustments of ventilation and moisture as of heat are not 

 required, that within limits (not definitely ascertained) these 

 may vary considerably without materially affecting the hatch. The 

 normal temperature of fowls is about 106, of other poultry about 

 the same. The temperature in natural incubation, therefore, would 

 be a few degrees lower, or the temperature at which eggs could be 

 kept with a body at about 106, applying heat from one side only. 

 The usual temperature of eggs under hens has been found to be 

 from 102 to 104, with a mean of 103. 



Antiquity of artificial methods. Artificial incubation has been 

 practiced by the Egyptians and Chinese for some thousands of 

 years. As developed by these peoples the appliances are crude 

 and the success of the process depends largely upon the judgment, 

 skill, and careful attention of the operator. Knowledge of the art 

 is confined principally to families in which it has been handed 

 down from generation to generation. Operations are on an ex- 

 tensive scale, and the operator remains with, and sometimes -in, 

 the " incubator " continuously throughout a period of incubation. 

 Modern artificial incubation as developed in America and Europe 

 is on different lines. The constant effort of the occidental inventor 

 has been to devise an incubator that might be operated by any one 

 anywhere, on any desired scale, and with the least possible per- 

 sonal attention. 



The problem in artificial incubation. To maintain a temperature 

 of approximately 103, with suitable atmospheric conditions, to 

 duplicate, as nearly as possible, in an artificially heated chamber, 

 the conditions to which an egg incubated by a bird is subjected, 

 is the incubator operator's problem. This problem presents two 

 phases. The first of these, the designing and construction of in- 

 cubators, is a matter for the inventor and manufacturer, and does 

 not directly interest the ordinary student. 



The individual potiltrymans problem in artificial incubation 

 is to take a " machine " which, when properly attended, is self- 

 regulating for heat, give it the attention requisite for this, and 

 adapt ventilation and moisture to local atmospheric conditions. 

 To reduce to the minimum the variations in these conditions, the 



