ARTlFlC5At. IXCUBATIO.V. 193 



When chickens are to be hatched to supply a regular consumption, 

 it will be best not to furnish the apparatus the first day wiih more than 

 the eggs necessary to yield a day's supply, and to add each day an e- 

 qual quantity during the first twenty days, and then to replace with eggs 

 the chickens hatched, in order to obtain the same number of chickens 

 daily, and to have the business regular through the year. 



We choose the freshest eggs, and reject all those which are more 

 than fifteen or twenty days old. Eggs grow stale sooner in summer than 

 in winter. We prefer the largest, because they give the largest and most 

 vigorous chickens. Those vvhich have two yolks should be rejected, 

 as well as those which have none, or which present other similar pecu- 

 liarities. Every egg which, seen by holding it up to the light, has a 

 very large void space, which can be rendered apparent by shaking, is 

 already old, and is not proper for incubation. There is no appreciable 

 sign to show whether eggs have been fecundated or not; the heat of in- 

 cubation, which gives to the transparent and clear matters contained in 

 tlie fruitful eggs a turbid and opaque aspect, after a lillle time enables 

 us to discover them. An egg not fecundated remains transparent after 

 several days of incubation, and sometimes during the whole period, 

 without manifesting any appreciable symptoms of putrefaction. 



2. Management of the incuhation. The eggs having been select- 

 ed, the day of the month is to be inscribed on the little end of each, 

 and they are to be arranged in the hatcher with the precautions already 

 mentioned. The eggs being placed, the vents and issues are to be closed 

 for a certain time to let the temperature remount, which the introduction 

 of the eggs and the opening of the apparatus have lowered, and after 

 this the thermometers are to be consulted to regulate it and maintain it 

 at the pi'oper pitch. 



The eggs once introduced, there are four circumstances to which we 

 must have regard, in managing the incubation : — The temperature of the 

 apparatus, the evaporation of a portion of the liquid parts of the eg^., 

 the respiration of the chickens, and their normal development. 



As to temperature, incubation can take place and succeed from 86° 

 Fahrenheit to 113°; but the most suitable temperature, that which gives 

 the greatest number and the most healthy and well organized chickens, 

 is that of 102° or 104° during the whole period of incubation. Physi- 

 ologists have indeed remarked that a temperature which is not suitable, 

 or which presents frequent variations, must either develop too rapidly, 

 or arrest in its course the development of the sanguino-respiralory sys- 

 tem, and that the chicken dies of atrophy in the first case, or of asphyx- 

 ia in the second ; or if not, presents strange disproportions in tlie differ- 

 So 



