On the source and the course of the embryonic blood circulation during development in the warm-blooded Vertebralia / by W. Macdonald.

  • Macdonald, William, 1797-1875.
Date:
1874
Catalogue details

Licence: Public Domain Mark

Credit: On the source and the course of the embryonic blood circulation during development in the warm-blooded Vertebralia / by W. Macdonald. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    To the accounts of the embryonic blood circulation, as given in the most popular anatomical books, showing their false and impossible anatomy and absurd physiology, I now refer, and from the important evidence which the develop- ment of the chick in ovulo-ovi affords as to the original course of the embryonic blood circulation during the earliest period of development, which cannot be seen in the case of the human embryo from its very minute size and the deep recesses where it first exists.* From the correspondence of the immortal Harvey, as translated by Dr Willis and published by the Sydenham Society, it appears that Aristotle says, the generation of the more perfect animals is made manifest by what occurs in the hen's egg, where all parts are not formed at once and together, but in succession to one another ; and that it is in virtue of a particular primary genital principle, that all these parts increase and grow by their own automatic force. Further on, in the same correspondence, he gives Aris- totle's view of the order of generation:— When conception takes place, the germ comports itself like a seed sown in the ground, for seeds likewise contain a first principle in potentia, which by-and-by manifests itself by sending forth a root by which aliment is taken up; so in conception, in which all parts of the body inhere in 20ote7itia, this first vital principle exists in special activity. This shows that, even in the earlier ages of the G-reek school, the value of the hen's egg during incubation was fully appreciated ; although the ideas of embryonic growth seem rather to have been adopted from conjectures that the embryonic blood circula- tion was similar to that of the adult, as had been demon- strated by Galen early in the course of the second century of the Christian era, fully established the anatomical knowledge of the human body, he seems to have confirmed * Professor Valentine, in his Physiology, as quoted by Wagner, describes the bird as the class of animal best adapted for examining the very early embryonic stages, not from any intrinsic quality of their own, but simply from the ease with which, at almost any season, a sufficient supply of fecundated hen's eggs for repeating the experiments of developing the chick in ovulo-ovi during incubation, as described by Dr Tonge.