Page:The Works of William Harvey (part 1 of 2).djvu/403

 EXERCISE THE THIRTY-SIXTH.

The perfect hen's egg is of two colours.

Every egg, then, is not perfect ; but some are to be held im- perfect because they have not yet attained their true dimen- sions, which they only receive when extruded ; others are im- perfect because they are yet unprolific, and only acquire a fertilizing faculty from without, such are the eggs of fishes. Other eggs again are held imperfect by Aristotle, because they are of one colour only, inasmuch as perfect eggs consist of yelk and albumen, and are of two colours, as if better concocted, more distinct in their parts, endowed with higher heat. The eggs that are called centenine or hundredth eggs, and which Fabricius 1 will have it are engendered of certain remainders of albumen, are of one colour only, and by reason of their de- ficiency of heat and their weakness, are regarded as imperfect. Of all eggs, there are none more perfect than those of the hen, which are produced complete in all their fluids and appendages, of proper size and fruitful.

Aristotle assigns the following reason wherefore some eggs are of two colours, others of one hue only : 2 "In the hotter animals those things from which the principles of their origin are derived, are distinct and separate from those which furnish their nutrition; now the one of these is white, the other is yellow/' As if the chick derived its origin from the albumen and was nourished by the vitellus alone. In the same place he proceeds thus : " That part which is hot contributes properly to the form in the constitution of the extremities ; but the part that is more earthy, and is further removed, supplies material for the trunk. Whence in eggs of two colours the animal derives its origin from the white, for the commencement of animal existence is in the white ; but the nourishment is ob- tained from the yellow." He consequently thinks that this is the reason why these fluids are distinct, and why eggs are produced of two colours.

1 Op cit. p. 10. 2 De Generat. Animal, lib. iii, cap. 1.