Considerations on the circulation of the blood : with special reference to counter-iritation [i.e. irritation], and to the effect of increased atmospheric pressure / by Andrew H. Smith.
- Smith, Andrew H. (Andrew Heermance), 1837-1910.
- Date:
- 1872
Licence: Public Domain Mark
Credit: Considerations on the circulation of the blood : with special reference to counter-iritation [i.e. irritation], and to the effect of increased atmospheric pressure / by Andrew H. Smith. 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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![capable of contracting under stimulus conveyed to them through a set of nerves distributed to them, and named from tlieir function the vaso-motor nerves. The contraction of an artery diminishes the supply of blood to the part to which the artery is distributed; while the contraction of a vein augments the resistance to the circulation and causes distention of the capilla- ries, and a prolonged sojourn of the blood in contact with the tissues. These varying actions arc made to subserve the purposes of nutrition, and function, and are presided over by the nervous system with a delicacy and accuracy so subtle and unerring as to seem like a localized intelligence, defying all attempts at analysis or explanation. This regulating power is of extreme importance, since the amount of blood required in any given part is constantly changing, and depends upon the activity of the part for the time being. Whenever an organ, before at rest, is brought into action, a demand is occasioned for an increased supply of blood, and the vessels leading to the part dilate to the extent required. I regard all function, with the exce]3tion of that of the or- gans of special sense, as the result of the chemico-vital reaction between the tissue of the acting organ and the blood which courses through its capillaries; and the nervous system as hav- ing no other ofSce in this regard than that of regulating the sup- ply of the nutritive fluid. Hence, blood being an essential fac- tor, and the quantity in the system being pretty nearly constant, it follows that a number of activities cannot be carried on sim- ultaneously for want of a sufficient supply of this necessary fluid. This conclusion, arrived at theoretically, is sustained by observa- tion. We find that a proper performance of the digestive func- tion is incompatible with great muscular activity; that the brain and the muscles cannot put forth at the. same time the maximum of effort; and, when a full meal has created a demand for a largely-increased circulation through the capillaries of the stomach and intestines, the brain is rendered anaemic, and drowsiness results. No two of the great emunctories of the system can be stimulated to excessive action at the same time. A diuretic and a diaphoretic will not act well together, nor will either act during the operation of a cathartic. These well- known facts are usually explained by assuming that the nerve-](https://iiif.wellcomecollection.org/image/b22300600_0002.jp2/full/800%2C/0/default.jpg)
