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.

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    on the uses of the yelk, and the apparent generation of earthy matter. Sir Everard Home and Mr. Hatchett have concluded, from their experiments, that the yelk is analogous to the milk of viviparous aimals, but more concentrated, and that its chief use is to afford a pabulum to the young animal during incubation.* This opinion, which is indeed as old as Aristotle,-f is corroborated in a striking manner by the present inquiry. Mr. Hatchett has also made the im- portant and curious remark, that in the ova of those tribes of animals, the embryos of which have bones, there is a por- tion of oily matter; and in those ova whose embryos consist entirely of soft parts, there is none. Hence it is concluded, that a certain portion of oil is necessary for the formation of bone. The present inquiry cannot be said to confirm, or invalidate, this remark, for although in the earlier stages of incubation, before ossification has commenced, a portion of the oil of the yelk is appropriated to the purposes of the economy of the animal, yet by far the greater portion of it remains ; and some of it is even retained by the yelk till its final dis- appearance.^ One great use of the yelk evidently is to fur- • Philos. Trans. Vol. 106, p. 301, et seq. -j- 'H jaev ouv ccp^Y) too vsottov egriv ex too Aeoxoo, q 8e Tgo^rj 81 a too ojaspaXoo ex too u%gou. Aristotelis de Animal. Hist. VI. 3. (Ed. Schneider.) Pliny makes the same remark. Ipsum animal ex albo liquore ovi corporatur. Cibus in luteo est. Hist. Nat. X. 53. J I examined a chick on the 18th day after incubation. The yelk was now re- duced to less than 2 grains, but it was of its original yellow colour, and of course contained oily matter. When burnt, it left traces of phosphate of lime. Dr. Macartney attempts to show that the yelk does not pass into the intestine through the ductus vitello intestinalis, but is taken up by absorption; and an argument he adduces in support of this opinion, is, that the earthy matter is left