7thly. In all paralytic cases, and such weaknesses where the strength of the body is already impaired.
8thly. and lastly, In the time of other evacuations of the body; as purging, fluxes, bloody fluxes, &c. and particularly when the body is in a sweat, or perspiration. From this, I hope, the good and bad effects of bleeding will be understood in many other cases, which would be too tedious to mention here; I shall therefore proceed to the operation of bleeding itself.
SECT. III.
Of the Operation of Bleeding.
Bleeding is thought in general to be a very simple performance; but in fact, there is not an operation in all surgery, requires more care, or is liable to more dangerous consequences, if ill performed.
It is not only the opening a vein, but it is to open it properly, (taking care not to prick an artery or tendon) to take away a sufficient quantity of blood, and to heal up the orifice again.
In the bend of the arm are three distinct veins, the head, median, and basilican. The ancients, before the discovery of the circulation of the blood, fancied the head, or upper vein, carried the blood from the head; the median, or middle, from the breast; and the basilican, from the liver, &c. but this idle conjecture is laid aside, as being highly absurd. When it is remembered what was said in the first Lecture, in Sect. V. of the circulation of the blood, it will then plainly appear, that all these veins become one before they enter the body; so that there can be no difference as to their quality in being opened: either therefore, which lays most conspicuously easy, is the vein that should be chosen; for the arms of people differ in this respect, as much as their features.
In order to chuse therefore properly, examine with the finger how the veins lie; if upon a flat hard substance, it is a tendon; if a pulsation is perceived, there is an artery; both which ought to be avoided if there is a vein that lays more free and conspicuous to the sight and touch. If however it cannot be avoided, the vein ought to be opened with the greatest caution, for the pricking of a tendon would not only be exquisitely painful, but endanger the arm by inflammation, and even life itself; and the pricking of the artery would endanger the patient’s bleeding to death, or else form an anauresma, (which is a bag of blood protruding from the artery) equally dangerous to the life of the patient. In general the middle vein is the safest and most convenient, provided it does not cross the tendon: for the upper vein lies frequently very deep, and is but small, and the lower frequently crosses a tendon, or lies immediately over an artery.
However, one or the other will frequently suit, and, with caution, the operation may be performed with ease.