When eggs which have been submitted to incubation permit light to shine through and show the yolk suspended in the upper half of the center as a clearly defined mass, which quickly reassumes its position in turning the egg with its long axis nearly horizontal, they are probably infertile or sterile. When, on the contrary, the yolk assumes indefinite outlines, approaching near the upper portion of the shell at the large end or appears with a thick spur upon its upper side, it may be regarded as having started to incubate. In the later stages the embryo can be plainly seen, because it becomes opaque and cuts off more of the light. In the incubation of eggs the candling is resorted to during the first few days of the experiment in order that the unfertilized eggs may be separated. The best time for the candling, if it is practiced only once, is on the sixth or seventh day of incubation. By that time all the eggs which are fertilized will be so changed as to be easily recognized by the candling process. Experience has shown that eggs which are more than two weeks old are not profitable for use in incubators since the percentage that does not hatch is so large. The incubating part of the plant is sometimes placed in the cellar over which the brooding house is built.
The brooding of young chicks is of the utmost significance. In Europe the changes in temperature are much less violent than in this country. The principal brooding houses in the United States are in the North where the temperature often falls in winter to below zero while in the summer it may rise to blood heat, a difference of over 100 degrees F. For this reason the incubating houses in the United States are often placed in cellars where the uniform conditions of temperature are more easily secured. There is no objection to this location provided proper care be taken to secure ventilation and the proper content of moisture in the atmosphere. In Great Britain the incubating houses are usually placed above ground instead of in cellars. The mean range of temperature in an incubating room in Great Britain, from March 12, 1903, to March 30, 1904, was 10 degrees. The highest temperature registered was 70 degrees on the 24th of June and the lowest 42 degrees in January. The humidity of the air was also quite constant, the lowest degree of humidity being 59 and the highest 94. These data show a very even temperature in the room itself. Of course the temperature in the incubator is necessarily greater, being that already referred to, namely 102 degrees.
Early Market.—One principal object in the raising of chicks is to force them to an early maturity in so far as size and palatability are concerned. The sooner the young broilers can be made ready for the market the more economy there is in their production. To this end they ought to receive a more abundant and specially prepared kind of food than if they were intended for ordinary farm purposes. In other words, the forcing process should be pushed as far as possible without interfering with the health and normal functions of the bird. Foods which are nutritious and stimulating and promote vigorous
