VENTILATION AND MOISTURE. 



83 



tester, the fertile germ is much more charac- 

 teristic, a small opaque spot being surrounded 

 by small red blood-vessels, clearly seen, branch- 

 ing from it. With practice these latter will be 

 seen earlier and earlier, even before any very 

 dark spot appears. Sterile eggs remain per- 

 fectly clear. Fertile germs which have died, or 

 addled eggs, present all sorts of appearances, 

 which need not be described, constant practice 

 being the best teacher ; but, generally speaking, 

 a red circle without branching veins, or a red 

 line near the side of the egg, denotes a dead 

 germ or broken yolk, and, later on, a sort of 

 floating dark mass surrounded by transparency, 

 spells " addled " to the tester. Let the learner, 

 however, mark all doubtful eggs, and then 



Fig. 49. — A Home-Made Egg-Tester. 



Ka^ily iiuvie t.'ith a bicycle lainf' and sheet 0/ zinc, or caidboard, 

 painted black, ami an aperture cut to size 0/ egg. 



observe how they turn out ; and in a short time 

 he will be surprised at the certainty with which 

 his tester will reveal to him the state of affairs. 

 It should be remarked, that whereas really sterile 

 eggs do no particular harm beyond perhaps 

 robbing live ones of heat which they require, 

 dead germs, being on the road to putrefaction, 

 are poison in the egg-drawer. Eggs with dis- 

 coloured shells, or v/ith exudation appearing, or 

 which smell offensively, should be removed 

 instantly, and it will be found that every one 

 will have been marked as at least doubtful, 

 beforehand, alter a very little experience. The 

 eggs should be tested again about the four- 

 teenth day. 



It does not answer well to fill up vacancies. 



made by testing, with fresh eggs. It can be 

 done, and if these are warmed up first, cooling 

 of the chamber by them can be avoided. But 

 as hatching proceeds, rather different conditions 

 of temperature and moisture prevail, and are 

 according to Nature's plan ; hence such mixtures 

 always impair the result. The eggs remain- 

 ing in a chamber should be either collected 

 or spread out equally ; else those close together 

 will be hotter than detached ones in another 

 part of the tray. 



Ventilation and moisture are essentially 



connected together, and there is now no doubt 



that both have been to a very 



Ventilation large extent overdone, each of them 



and ■ 1 . 1-1 



Moisture. ownig to that connection. h.arly 



incubators were made with close 

 chambers, and practically no ventilation at all ; 

 naturally the want of fresh air caused failure, 

 and great improvement immediately followed 

 the introduction of free openings tor exit, 

 and inlets for the air, the latter being usually 

 at the bottom of the machine. This arrange- 

 ment causes the most rapid circulation of 

 all ; and as evaporation is in direct propor- 

 tion to the movement of drier air over the 

 evaporating surfaces, the eggs were rapidly 

 dried up, and many chicks glued to the shells. 

 For this the remedy was " moisture," which was 

 given freely in various ways : by cold tanks 

 at the bottom, damping earth or sand in a tray 

 under the eggs, or water-trays at the top of the 

 chamber. Great success was now very often 

 attained, and it was natural for it to be thought 

 that free ventilation and moisture " was the 

 great secret "of successful hatching. To such 

 an extent was this belief at the time held that 

 some incubator users considered that if the 

 moisture in the egg-drawer were increased, the 

 greater would be the number of eggs hatched. 

 On the direct contrary, from queries and dead 

 eggs which have been sent to us during many- 

 years, there can be little doubt that more dead 

 chicks have resulted from too much moisture 

 than from any other cause, and incubator users 

 will do well to note this. 



The djie proportion between ventilation and 

 moisture is no doubt, next to proper heat, the 

 cardinal point ; but the whole matter has had 

 to be cleared up by fresh investigation, and has 

 now been completely elucidated by the far 

 larger experience of operators and manufacturers 

 in the United States. While temperature re- 

 mained variable to the extent of several degrees 

 from atmospheric conditions, occasional (and 

 often unknown) overheating was again and again 

 in a measure rectified by cooling and airing ; 

 but this is now better guarded against either by 



