1821.] Dr. Paris on the Physiology of the Egg. 5 



sles, as far as we are able, in a state of complete inactivity; 

 nothing could have been more judicious than the advice given 

 by Mr. Holwell to his unfortunate fellow sufferers in the Black 

 Hole at Calcutta, " not to exhaust their strength by useless efforts, 

 but to remain quiet and orderly, " or in other words, not to waste, 

 wantonly, the animating principle of the atmosphere by motions, 

 the effect of which is to render an increased consumption of it 

 unavoidable : on the contrary the expedients resorted to upon 

 that melancholy occasion, were calculated to accelerate the 

 fatal result which they were intended to counteract, such as 

 fanning the air with their hats, and kneeling down, for the pur- 

 pose of simultaneously rising, in order to give a fresh impulse 

 to their stagnant atmosphere. 



It is evident that the inflation of the follicul us aeris of the ego- 

 will proceed in the same ratio as the evaporation of its fluid con- 

 tents : the importance of such an arrangement is sufficiently 

 obvious. I shall, therefore, proceed to describe the shell, the 

 only part of the egg which now remains to be noticed. The use 

 of the shell is not only to defend the ovular structure from 

 external violence, but to regulate the evaporation of the fluid 

 contents, and the various chemical changes essential to its deve- 

 lopement. It consists, according to the latest experiments of 

 M. Murat Guillot,* of gelatine 3, phosphate of lime 2, carbonate 

 of lime 72 parts, united to an organic tissue. Mr. Carlisle, in a 

 memoir read before the Royal Society, " Upon the Vascular 

 and Extra -vascular Parts of Animals," states, that the calca- 

 reous shells of birds' eggs are merely deposited upon the mem- 

 brana putaminis, and that the inner portions are regular crystal- 

 lized prisms, the long diameters of which point to the centre of 

 the egg. I have repeatedly endeavoured to discover such a 

 crystalline structure, but unsuccessfully ; and my friend Mr. 

 William Phillips, whose knowledge of crystallography is so 

 justly appreciated, has examined the egg shell with no better 

 success. The hard and brittle texture of the shell is increased 

 by incubation, and it also undergoes some other changes during 

 this period which are not well understood. 



Every circumstance connected with incubation discovers an 

 evident design to conceal the bird and its egg : the hen in ■ 

 general is not dressed in the gaudy plumage which distinguishes 

 the male, nor is she endowed with the talent of singing, lest her 

 note should arouse the vigilance of her enemies: so the colours 

 of the egg vary in the different species of birds, and seem well 

 adapted to the purpose of concealment. " Thus," says Dr. Dar- 

 win, " the eggs of hedge birds are greenish with dark spots; 

 those of crows and magpies, which are seen from beneath 

 through wicker nests, are white, with dark spots ; and those of 

 larks and partridges are russet and brown, like their nests and 

 situations." 



The matter from which the shell is formed is secreted in the 



" Annates de Cluiuie, vol xxxiv 



