On the principle of vitality. A discourse delivered in the First Church in Boston, Tuesday, June 8th, 1790. Before the Humane Society of the Commonwealth of Massachusetts / By B. Waterhouse, M.D.

  • Waterhouse, Benjamin, 1754-1846.
Date:
1790
Catalogue details

Licence: Public Domain Mark

Credit: On the principle of vitality. A discourse delivered in the First Church in Boston, Tuesday, June 8th, 1790. Before the Humane Society of the Commonwealth of Massachusetts / By B. Waterhouse, M.D. Source: Wellcome Collection.

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    Now, a living animal has, befides thofe attributes common to all bodies, as folidity, extencion and gravity, a peculiar fomethings which dittinguifhes it from a dead one ; tor a mufcular fibre wiil contract, and that not by the power of gravitation, cohefion, chryftaliization, magnetifm, or che¬ mical attraction. That to be only one ; each wrapped up in a membrane of it’s own, one white within the other, In the midfl: of all is the yolk, wrapt round likewifewith i’s own mem¬ brane. At each end of this are two ligaments, called chalazee, which are white denfe fubftances, made from the membi anes, and ferving to keep the white and the yolk in their places. The cicatrlcula is the part where the animal firft begins to (hew figns of life ; it refembles a vetch or fm<dl pea, lying on one fide of the yolk and within its mem¬ branes. The outer membranes and ligaments pieferve the fluids in their proper places* the white ferves as nouriihmenc • and the yolk with its membranes^ after a time, becomes a part of the chicken’s body This is the defcription of the ben's eggt and anfwers to all others, how large or how fmail foever. Previoufly to putting the eggs to the hen, JVlalpighi and Haller firft examined this cicatricula, which they confider as the moll important part of the egg This (which fome call the punttum faliens or punftum vit#) was found in thole that were im¬ pregnated by the male to be large, but in others fmail. Upon examination with the microfcope it was found to be a kind of bag, containing a traofparent liquor, in the midft of which the embryo was feen. The embryo refembled a compoiition of little threads, which the warmth of future incubation tended to enlarge. Upon placing the egg in a proper warmth, after fix hours the vital [peck begins to dilate like the pupil of .he eye. The head of the chicken is diflinftly feen, with the back-bone fomething refembling a tadpole floating in its ambient fluid, but as yet feeming to aflume none of the fun&ions of animal life. About fix hours more the little animal is feen more difiindlly ; the head becomes more plainly vifible, and the vertebrae of the back more eafily perceivable. All thefe figns of preparation for life are encreafed in fix hours more ; and, at the end of 24, the ribs begin to take their places, the neck begins to lengthen, and the head to turn to one fide. At this time, the fluids in the egg feem to have changed place ; the yolk which was before in the center of the (hell, approaches nearer the broad end. The watery, . part.