RESPIRATION OF THE EMBR YO. 



733 



and was probably in the last three weeks of iiitra-uteriiie life. The result 

 was 



Oxygen 



Carbon dioxide 

 Nitrogen 



6 '669 volumes per cent. 

 46-542 

 1-000 



Total gas 



54-211 



Comparative estimations of the gases in the umbilical artery and 

 vein were also made, and show that the changes undergone by the blood 

 in the placenta are about one-half as marked as in the lungs of an 

 adult : 



From these results Cohnstein and Zuntz calculate that the absorp- 

 tion of oxygen by a foetal sheep weighing 3600 grms. is 175 c.c. per 

 minute, or, per kilo, and minute, 049 c.c., which is about one-twelfth the 

 amount absorbed, weight for weight of body, by a full-grown sheep. 



The respiration of the embryo. The process of respiration in the 

 embryo has, owing to the natural difficulties of the subject, been chiefly studied 

 in the eggs of birds and of a few reptiles. The absorption of nitro-aerial gas 

 (oxygen) through the porous shell of an egg undergoing incubation appears 

 to have been first recognised by Mayow, 2 but the necessity of respiration in 

 the developing embryo was first shown by the experiments 3 of varnishing 

 the eggs, covering them with oil or warm water ; under such conditions it was 

 found that the embryo quickly ceased to develop, and died. If the impervious 

 covering was only applied to a portion of the shell, the embryo developed, in 

 some cases normally, in others abnormally with the production of deformities 

 or monstrosities. 4 



1 Zuntz, Hermann's " Haiidbucli," Bd. iv. Th. 2, S. 37. 

 "Tract, quinque," Oxonii, 1674, pp. 131, 313, 321. 



3 Paris, Ann. PhiL, London, 1821, N.S., vol. ii. p. 2 ; Home, Phil. Trans., London, 

 1810, p. 213 ; 1822, p. 339 ; Dareste, Ann. d. sc. not., Paris, 1855, Ser. 4, Zool., tome iv. 



L119 ; Compt. rend. Acad. d. sc., Paris, 1855, p. 963 ; Marshall, Med. Times and Gaz., 

 ndon, 1840-41, vol. i. p. 242 ; Dusing, Arch. f. d. ge*. PhysioL, Bonn, 1884, Bd. 

 xxxiii. S. 67. Here other references are given. 



4 Gerlach and Koch, BioL CentralU., Erlangen, 1882, Bd. ii. S. 681. 



