Observations on the changes produced in the blood &c / by Charles J.B. Williams.

Date:
[1835]
Catalogue details

Licence: Public Domain Mark

Credit: Observations on the changes produced in the blood &c / by Charles J.B. Williams. Source: Wellcome Collection.

Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.

    18/44 (page 18)
    uncertainty as to the precise constitu- tion of the red particles will not permit us to entertain any decided opinion. The change in colour in the red g'lobule may proceed either from a change in the colouring matter itself, or from some alteration in the central globule, caus- ing it to reflect lig-ht more copiously, which, transmitted through the red co- louring matter, g-ives a crimson of a brighter hue. Although the first of these has probably the greatest share in producing this effect, I think it likely that tbe other may co-operate; for a thin film of venous blood, when viewed on a white surface, appears to be of the same colour as arterial blood. Tbe change in the central globule capable of answering this end, is the acquisition of a degree of solidity and white opacity; and that this really occurs seems proba- ble from tbe fact that arterial blood is less transparent than venous. Whilst the presence of oxygen in the blood is enough to give it the arterial hue, tbe true venous colour is produced by the absence of oxygen, and the pre- sence of carbonic acid. From some ex- periments I have been led to conclude that the venous blood from which car- bonic acid has been abstracted is of a deep lake colour, and that the brownish tint present in venous blood in its na- tural state is to be attributed to tbe pre- sence of this gas. Synthetic experi- ments likewise confirm this notion. [On the subjects of the foregoingpas- sages some new facts have been pre- sented in tbe work of Dr. Stevens* ; but although these possess much practical interest, they do not appear to me to elucidate the theory of respiration further than the views given above. We may well devote a little attention to tbe lead- ing points brought forward by Dr. Ste- vens, and to tbe views which he founds upon them. I have stated it as well known that the colouring matter of the blood, when quite deprived of scrum, does not become florid as usual on ex- posure to the air. Dr. Stevens finding that various saline solutions, as muriates of soda or potash, and carbonates of soda and potash, nitrate of potash, &c. have the property of giving a most flo- rid arterial colour to dark crassamen- tum, concludes that the usual change on exposure to air depends more imme- diately on the saline matter of the scrum than on the oxygen of the air. It has been long known that acids have the effect of darkening the colour of the blood; and Dr. Stevens ascribes the dark colour of venous blood solely to the carbonic acid which it coutains, and which counteracts the reddening pro- perty of the salts of the serum. He sup- poses that the oxygen of the air produces the reddening effect generally referred to it, by drawing- away this carbonic acid by some unknown power of attrac- tion, and thus restoring to the salts of serum their wonted reddening property. In illustration of these points he mixed blood with Saratoga water (a saline mi- neral waterstrongly charged with carbo- nic acid): the immediate effect was to darken the blood ; but after a short ex- posure to the air, it rendered it bright and scarlet. It will occur, however, to those fami- liar with the chemistry of this subject, that Dr. Stevens’s conclusions, assum- ing as they do the existence of an un- known and novel power of attraction, are by no means warranted by the facts in question. I am not prepared to deny that the saline matter of serum may be concerned in giving brightness to the colouring matter; but in the case of the action of the air on the blood, this is by no means proved to be the sole cause of the change. Saline solutions of various kinds will certainly redden dark blood in a very remarkable manner; and this quite independently of the contact of the air: but oxyg-en seems also to have a similar effect, independently of its power of removing carbonic acid. We know that other gases can disengage carbonic acid from venous blood ; yet neither these nor the air-pump can give to it the arterial hue. Again, if free carbonic acid alone caused the darkness of venous blood, its operation should be suspended, and the reddening power re- stored to the salts of serum, by adding a small quantity of a pure alkali, just enough to neutralize it. I have many times made this experiment with great care, beginning with the smallest quali- ties of liquor potassre, and trying it in various proportions; but I have never been able by this means at all to brighten the colour of venous blood. When tbe quantity of alkaline solution exceeds a few drops, it gives the blood a browner and duskier hue, which is ob- viously from the free alkali effecting a permanent change in the colouring mat- * On tlie Blood, 1833.