The vitality of the blood : proved by physiological experiment, and its application to veterinary pathology demonstrated / by J.S. Gamgee.

  • Gamgee, Sampson, 1828-1886.
Date:
[1849?]
Catalogue details

Licence: Public Domain Mark

Credit: The vitality of the blood : proved by physiological experiment, and its application to veterinary pathology demonstrated / by J.S. Gamgee. 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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    the most striking changes presented in the evolution of the mara- maUan embryo, more particularly elucidating those which relate to the vascular system. That the existence of the ovarian ovum in mammalia is essen- tial to the propagation of their species was first maintained by De Graaf in 1690; but subsequently opposed by the ingenuous Haller, who prevailed over the Dutch physician in the opinion that the ovum was first formed in the Fallopian tube out of a sub- stance emitted from the ovary. Sixty years since, Cruikshank ineffectually attempted to revive De Graaf's theory, which, how- ever, remained in abeyance until 1827 ; when Von Baer discovered the mammalian ovulum in the ovary, erroneously considering it as analogous to the germinal vesicle of oviparous animals. This statement was contradicted by Coste and Wharton Jones, who clearly demonstrated that the ova of mammalia, like those of birds, contain a germinal vesicle perfectly distinct but propor- tionately smaller. The ova in the ovary are contained in Graafian vesicles, lined by the membrana granulosa, which is composed of granules ar- ranged in linear series : each ovum consists, first, of an external, thick, but transparent envelope, the zona pellucida; secondly, the yolk; thirdly, the germinal or Purkinjean vesicle; fourthly, the germinal spot or macula germinativa, first observed by Wagner. [See Fig. I, PL 1.] In harmony with the researches of Purkinje in birds. Dr. Martin Barry has shewn that, in mammiferous animals, the germinal vesi- cle (consisting of a structureless membrane, distended with an albuminous fluid, and having attached to its walls a Granular ger- minal spot) is the first formed element of the ovum. Bischofl^, on the other hand, accords the priority of formation to the Graafian vesicle; but, comparing the experiments from which these infer- ences were drawn, we are inclined to favour the opinion of the Eng- lish embryologist. By aggregation of oil-like globules and gra- nules, the yolk surrounds the germinal vesicle, and acquires a vitelline membrane or zona pellucida. The production of ova is said to commence, in the cow and sow, at an early period of intra-uterine life, but not until birth in the human species, dog, and rabbit. The position of the several parts of the ovum varies in attain-