Page:The Works of William Harvey (part 1 of 2).djvu/655

 circumstances, (than within an animal), it is then denominated an "egg," or "worm." I think, however, that in either case the word "primordium" should be used to express that from whence the animal is formed; just as plants owe their origin to seeds: all these "primordia" have one common property—that of vitality.

I find a "primordium" of this kind in the uterus of all viviparous animals before any trace of a fœtus appears: there is a clear, thick, white fluid (like the albumen of the egg) inclosed in a membrane, and this I call the ovum. In the roe, fallow-deer, sheep, and other cloven-footed animals, it fills the whole uterus and both its horns.

In process of time an extremely limpid and pure watery fluid (similar to that which in the hen's egg I have called the colliquament) is secreted by this "primordium" or "ovum;" in clearness and brilliancy far exceeding the remaining fluid of the ovum in which it is contained. It is of a circular form, and inclosed in a very delicate and transparent membrane of its own called the "amnion." The other fluid, of a denser and thicker character, is contained in the outer envelope, or chorion, which is in immediate contact with the concave surface of the uterus, and which also encompasses the entire ovum: the shape of this second membrane varies according to that of the uterus: in some animals it is oval, in others oblong, but in those with cloven feet it resembles a saddle-bag. After a short time a red pulsating point shows itself within the transparent substance, and from this point exceedingly fine twigs, or rather rays of vessels, start forth. By and by the first aggregated portion of the body makes its appearance, folded upon itself orbicularly, and somewhat resembling a grub: the remaining parts follow in the order described in our history. For I have ascertained that the production of the fœtus from their ova or "conceptions" in viviparous animals, takes place exactly in the same way as the growth of the chick within the egg.

As I before observed, "conceptions" in viviparous animals vary in form, number, and in their modes of attachment to the uterus. At first, especially in the cloven-footed animals, the "conception" does not adhere to the uterus, but is only in contact with, and fills and distends the organ, and can be easily