Some experiments on the changes which take place in the fixed principles of the egg during incubation.

  • Prout, William, 1785-1850.
Date:
1822
Catalogue details

Licence: Public Domain Mark

Credit: Some experiments on the changes which take place in the fixed principles of the egg during incubation. Source: Wellcome Collection.

Provider: This material has been provided by Royal College of Physicians, London. The original may be consulted at Royal College of Physicians, London.

    25/26 (page 23)
    nish the phosphorus, entering as phosphoric acid, into the skeleton of the animal; but that the earthy portion of the bones is derived from the transmutation of oil into lime can- not, perhaps, be safely asserted in the present state of the inquiry. With respect to the earthy matter found in the skeleton of the chick when it quits the shell, I think I can venture to assert, after the most patient and attentive investigation, that it does not pre-exist in the recent egg; certainly not, at least in any known state. The only possible sources, therefore, whence it can be derived, are from the shell, or transmutation from other principles. Whether it be actually derived from the shell, cannot be determined by chemistry; because, as we have seen, the shells of different eggs differ so much, that the application of averages is out of the question ; and we are of course precluded from ascertaining the exact quantity of lime any particular shell originally contains. There are, however, very strong reasons for believing that the earthy matter is not derived from the shell. In the first place, the membrana putaminis never. becomes vascular, and seems analogous to the epidermis ; hence the lime of the shell, which is exterior to this membrane, is generally considered by phy- siologists as extra-vascular ;* it is therefore extremely difficult behind in the yelk. In the present instance, however, the quantity of earthy matter was very minute: it had therefore disappeared, as well as the other principles of the yelk. When the chick is younger, the quantity of earthy matter is said to be much larger. Haller asserts that the yelk disappears about the 16th day ; and Aristotle long ago remarked, that very little of it was left on the 10th day, after the chick had left the egg. * See an Essay “ on the connection between the vascular and extra-vascular parts of animals,” by Sir A. Carlisle. Thomson’s Annals, Vol. VI. p. 174.