RESPIRATION OF THE EM BR YO. 
733 
and was probably in the last three weeks of intru-uterine life. The result 
was — 
Oxygen 
Carbon dioxide 
Nitrogen 
6 - 669 volumes per cent. 
46-542 „ 
1-000 „ 
Total eas 
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 : — 
Oxygen. 
Carbon Dioxide. 
Fcetal . 
Sheep 
' Artery 
Vein 
Difference . 
Artery . . 
Vein 
» Difference . 
6 '69 vol. p.c. 
less than 11*36 ,, 
4-67 ,, 
2-3 „ 
6-3 
4-0 
45 "54 vol. p.c. "\ Specimens 
of blood 
41-82 ,, V taken sim- 
ultaneous- 
ly ,, J ly. 
4 -. -a Sample of 
blood from 
40 .f. 1 vein taken 
I 24 minutes 
fi . - after that 
" J fromartery. 
[D i fference 
Adult J between ven- 
animals : J cms and ar- 
l terial blood 
8 '15 vol. p.c. 
t>'2 vol. p.c. 
From these results Cohnstein and Zuntz calculate that the absorp- 
tion of oxygen by a fcetal sheep weighing M600 grms. is 175 c.c. per 
minute, or, per kilo, and minute, 0'49 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 " Haudbuuh," Bd. iv. Th. 2, S. 37. 
2 "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. 
p. 119 ; Compt. rend. Acad. d. sc, Paris, 1855, p. 963 ; Marshall, Med. Time* and Gaz., 
London, 1840-41, vol. i. p. 242 ; Dusing, Arch. f. d. ges. Physiol., Bonn, 1884, Bd. 
xxxiii. S. 67. Here other references are given. 
4 Gerlach and Koch, Biol. Ccniralbl., Erlangen, 1882, Bd. ii. S. 6S1. 
