EGGS VARNISHED OVER, 293 



oxygen was reduced, and that a portion of carbonic 

 acid was added to the air. From these experi- 

 ments it has been argued that the chick respires 

 some of the air contained in the air-follicle at the 

 broad end of the egg. 



Several curious experiments, some of them how- 

 ever remarkably contradictory in their results, 

 have been performed upon the respiration of eggs. 

 It has been said that if eggs are varnished over, 

 or coated with oil, the chick will perish in conse- 

 quence of the interruption to its respiration. In 

 warm water also the development of the eggs of 

 birds is not maintained, nor in gases which are 

 irrespirable. M. Schwann found that when eggs 

 were kept at the proper temperature in gases 

 which contained no oxygen, a slight change in the 

 germ takes place, but no blood is formed. Eggs 

 confined in pure hydrogen gas, if kept at incu- 

 bating heat for thirty hours, were killed alto- 

 gether; for twenty-four hours they could still be 

 developed if admitted to atmospheric air. Other 

 observers state, however, that they have kept 

 eggs in irrespirable gases without injury to the 

 germ, and that it has been developed when kept 

 at the proper temperature of incubation. 



