Licence: In copyright
Credit: Arterial hypertonus, sclerosis and blood-pressure. Source: Wellcome Collection.
Provider: This material has been provided by Royal College of Physicians, London. The original may be consulted at Royal College of Physicians, London.
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![be it remembered, not necessarily In-ougbt about through the nervous system. As the capillaries contract as well as the arteries, the “ stop-cock ” theory of Dr, George Johnstone must yield to the more prosaic view that arteriole contraction is but part of a wider contraction, and is not a special arrangement for saving the capillaries. If we are to retain any part of this attractive conception, it will require to be so modified that arteriole and capillary contraction may be regarded as a provision for diminishing the supply of an impure blood to the tissues. This is really a truer conception, for it is the good of the tissues which is the aim of the circulation, and this vessel constriction not only protects directly, but also indirectly, by lu'oducing symptoms which can lead to what we may call blood purification. The mechanical views of the circulation have had their day, and have effected their purpose almost too well; it is now time’ that we should think of tlie vessels as livinfi tubes, contracting not only under the influence of nerve centres, but under the direct stimulus of substances present in the circulating blood—contraction so caused being the hyper- fonus and the hypertonic contraction of pur argument, as much as when it is a response to nerve iuipulsgs. THE LOCALISATION OF THE ACTION ON THE VESSEL WALL The fact tliat arterial conti'action can be determined l)y l)lood com])osition, or by blood-content, lias, as has lieen already said, but little iullueuced practical medicine, it is therefore all the more necessary not only to show, as I have Just done, tliat tlie proposition is supported by the weight of physiological investigation, as surely as the action of the sympathetic nervous system is established, Imt to see how much further ])hysiological investigation and experiment will allow us to go. It will bo seen that ex])eriniontal investigations still further warrant and support our clinical contentious; and they ought, 1 think, to satisfy and convince those who have hitherlo thought uf vessel contraction anil of blood-](https://iiif.wellcomecollection.org/image/b28036591_0066.jp2/full/800%2C/0/default.jpg)
