United States or Réunion ? Vote for the TOP Country of the Week !
The power of attraction which the ovum exerts may be likened, most simply, to the influence of a magnet upon iron-filings. While there has been no opportunity to observe such attraction between the parent cells of human beings, its existence is not open to doubt.
We will now compare the embryonic development of the two animals, and find to our great astonishment that the same embryonic form develops from the ovum of the Amphioxus as from that of the Ascidia a typical chordula.
Now as the first filament of entity cannot be furnished with the preparative organs above mentioned, the nutritive particles, which are at first to be received by it, are prepared by the mother; and deposited in the ovum ready for its reception. These nutritive particles must be supposed to differ in some respects, when thus prepared by different animals.
The material prepared for the reception of the ovum is used to nourish the new life if pregnancy occurs, but when it does not, this surplus passes off in the form of the menstrual flow. The menopause or change of life is the end of the child-bearing period of a woman's life. The average age at which it occurs is forty-six, although there is a great difference as to this.
Within these lobules the spermatozoa are formed by a complex process of cell division and cell germination upon whose description we need not enter here. The spermatozoon may be described as the male sexual cell whose function is to fertilize the female ovum. The spermatozoon is about 1/20 of an inch in length and consists of a head, body and a vibratile tail.
In parthenogenetic ova this happens without conjugation with a spermatozoon at all: in other cases, since the zygote is compounded of spermatozoon and ovum, we can only say that in the XX zygote, the ovum developing only ova, the female is dominant, in the X or XY zygote developing only spermatozoa the male is dominant.
On the other hand, in some of the eastern countries menstruation was regarded as sacred, and the first menstrual discharge was considered so valuable that premenstrual marriages were inaugurated in order that the first ovum might not be wasted, but fertilized, because it was supposed to be the purest and best for the purpose.
While it is not certainly known, it is probable that the ovum is capable of impregnation any time during its sojourn within the oviduct and before reaching the uterus, or probably for a period of about one week from the time of its escape from the Graafian follicle.
How comes it then that the female quality entirely disappears? Whether the gametocytes are distinguishable at an early stage in the segmentation of the ovum, or only at a later stage of development, we know that the gametes ultimately formed have descended by a series of cell-divisions from the fertilised ovum or zygote cell from which development commenced.
By parity of reasoning each living form now on the earth must be able to claim identity with each generation of its ancestors up to the primordial cell inclusive. Again, if the octogenarian may claim personal identity with the infant, the infant may certainly do so with the impregnate ovum from which it has developed.
Word Of The Day