EGGS. 



369 



The eggs of birds also maintain a process of respiration, even 

 in the unincubated state ; fresh eggs, on exposure to the air, con- 

 tinuously exhale carbonic acid and aqueous vapour, and hence they 

 lose considerably in weight when kept for some length of time. 

 But they also absorb oxygen, as is more especially shown by the 

 circumstance that the air inclosed in the air-space contains more 

 oxygen than atmospheric air, according to Bischoff* from 0'22 to 

 0-245 J, and according to Dulkf from 0'25 to 0'27-g- (by volume) ; 

 but this has been denied by Baudrimont and Martin St. Ange. 

 The process of respiration becomes more active after incubation, 

 as is obvious from the circumstance that the development of the 

 embryo is very soon arrested and that death ensues in hydrogen 

 or carbonic acid gas, as is shown by the experiments of Viborg, 

 Schwann,J and Martin St. Ange. The greater part of the oxygen 

 in the air-space disappears during incubation, and the air is then 

 frequently found to contain about 6jj- of carbonic acid. The more 

 recent experiments of Baudrimont and Martin St. Ange have 

 shown, in reference to the interchange of gases during the incuba- 

 tion of hens 5 eggs, that in proportion as the embryo becomes more 

 fully developed, a larger amount of oxygen is absorbed from the 

 atmosphere and more carbonic acid given back to it. Here also 

 the quantity of oxygen contained in the carbonic acid falls far 

 short of the absorbed oxygen. The experiments of Valenciennes 

 have proved that here too the respiration is accompanied by a 

 liberation of heat. The following table gives the results of the 

 experiments, instituted by two of the observers already referred to, 

 on eggs ; but here the total loss of weight in the eggs, owing to 

 the chloride of calcium in the apparatus, no doubt greatly exceeds 

 the normal quantity. 



* Schweigger's Journ. N. R. Bd. 9, S. 446. 



f Ibid. 1830, p. 363. 



J De necessitate ae'ris atmosph. ad evolut. pulli in ovo. Berolini, 1834* 



Compt. rend. T. 17, p. 1343. 



VOL. III. 2 B 



