An inquiry into the nature and properties of the blood, in health and disease ... / [C. Turner Thackrah].
- Charles Thackrah
- Date:
- 1834
Licence: Public Domain Mark
Credit: An inquiry into the nature and properties of the blood, in health and disease ... / [C. Turner Thackrah]. Source: Wellcome Collection.
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![difference in these estimates seems to depend on the want of such data as are requisite for accurate research. It is true, indeed, that the contents of the principal arteries and veins may be subjected to calculation, but of the blood circulating in the capillaries no accurate estimate can be formed. When we reflect on the minuteness of these capillaries, on the universality of their distribution, and on the large proportion which they constitute of muscle and other solids; when we remark, also, the red colour which the flesh of a slaughtered animal retains, we must refuse to admit any estimate formed from the quantity of blood drawn off in fatal hemorrhage. The blood, moreover, cannot be obtained in toto, without the admix- ture of its secretions. If we collect the blood of a slaughtered animal, our estimate is invalidated by the changes which take place during the period, and especially by the water, or a serous fluid, which is largely absorbed into the circulation during hemorrhage. But if we cannot precisely ascertain the proportion of blood, we may form some opinion of the amount of the circulating fluids, by macerating the slaughtered animal till the red colour is nearly lost, and deducting the loss by hemorrhage and maceration from the whole weight. This, however, can only be considered as an approach to the truth. If a drop from crassamentum, or coloured serum, he placed between two pieces of glass, and examined with a powerful microscope, we see an interesting arrangement only, while others include all the animal fluids in the computation. The statement of Sir A. Cooper refers not to the absolute amount of blood, but to the proportion that may be withdrawn before death ensues. ‘ The proportion of blood, compared with the solids, which can be drawn from an animal before it dies, is about one pound to sixteen.” Lectures on Surgery, No. IV. It is rather surprising that an intvestigator, so generally accurate as Mr. Thackrah, should have been thus incorrect: especially as an experiment of his own is widely at variance with these calculations. See Appendix II. Exp. I, Ep.]](https://iiif.wellcomecollection.org/image/b33094457_0040.jp2/full/800%2C/0/default.jpg)
