308 Dr Parıs’s Remarks on 
“which it is hereafter to become, receives air through the medium 
of spiracula, dispersed over the exterior involucrum. The de- 
scription of the folliculus acris just delivered is taken from that 
in the egg of our common hen. ‘The same apparatus exists in 
the eggs of all birds, and contains a similar air: its capacity, 
however, does not seem to vary either with the size of the egg, - 
or of the bird to which it belongs ;. but I think I have discovered 
a beautiful law by which its extent is modified. 
Ihave uniformly found, as far as my contracted inquiries have 
led me, that the folliculus acris is of greater magnitude in the eggs 
of those birds which place their nests on the ground, and whose 
young are hatched fledged, and capable of exerting their muscles 
as soon as they burst from their shell, than in the eges of those 
whose nests are generally built on trees, and whose progeny are 
born blind and forlorn. Thus the folliculi in the eggs of fowls, 
 partridges, and moor-hens are of considerable extent, whilst 
those in the eggs of crows, sparrows, and doves are extremely 
contracted. "The chick, therefore, of fowls and partridges has a 
more perfect plumage, and a greater aptitude to locomotion, 
than the callow nestlings of doves and sparrows. . Such an 
instance of the agency of oxygenation in the promotion and 
increase of muscular power is not solitary in physiology; for the 
history of ruminating animals will furnish us with a parallel 
example. “Their cotyledons,” observes the author of Zoonomia, — 
“seem to be designed for the purpose ofii g a greater - 
surface. for the termination of the placental vessels, i in order to 
receive oxygenation from the uterine ones: thus the progeny 
of this class of animals are more completely formed before their 
nativity than that of the carnivorous classes. Calves therefore 
and lambs can walk about i in a few minutes after their birth ; 
bile: kittens and puppies remain many days without opening 
du their 
