£64 Mr Ritchie on ascertaining the Sex of the Chick in Ovo. 
by Dr Autenreith jun. of Tubingen. From his experiments 
it appears, “ that the opinion so generally entertained by 
his countrymen, that cocks are contained in the longer eggs, 
and hens in the shorter and rounder ones, is without founda- 
tion ; for the sex is indicated neither by the shape nor by the 
size, nor in any way by the external form of eggs 
A French naturalist, Bory de St Vincent *f, speaks of a phy- 
sician who had examined many thousand eggs, without being 
able to ascertain, from their external appearance, whether they 
contained cocks or hens. 
Eggs of the same bird differ from each other in specific gra- 
vity. It has been conjectured, that the heavier eggs may con- 
tain males, the lighter ones females. But it is now generally 
known that eggs lose weight by being kept ; and it has been 
shewn that this diminution arises from “ the substitution of air 
for a portion of the water of the egg which escapes J.” 
Eggs were found by Dr Prout to differ from each other in 
the relative proportions of their saline principle. “ I have some- 
times thought,” says he, t£ these differences, as well as some 
other singular ones observed with respect to the earthy matters, 
might be connected with the sex of the future bird but he 
adds, u no proof of this could be obtained §.” 
I have heard of a mode of discovering the sex of the chick in 
ovo, different from any which has been proposed by naturalists. 
The folliculus aeris, or air-cell, which is to furnish oxygen to 
the future chick, is situated at the larger end of the egg. It 
has not in all eggs the same position at the larger end ; and in 
various districts of Scotland, it is believed that eggs having the 
air-cell situated exactly at the top of the larger end, produce 
males ; while those having the air-cell only near the top of the 
larger end produce females. 
To ascertain this, I instituted a series of experiments. These 
experiments, as will be seen, go very far to prove, that the 
opinion which has been stated is correct, and so to determine 
what naturalists of Germany, France, and England, have en- 
deavoured in vain to discover. 
• Dissertatio Inauguralis, p. 26. Tubingen 1821. 
-f- Voyage de St Vincent , p. 64. Paris 1804. 
X Phil , Trans, for 1822, p. 3T8. 
§ Ibid, p. 386. 
