The manner of bleeding, whether by opening a vein or an artery, is a surgical subject, which it is not necessary to consider in this work.

Physiological Actions

Bloodletting may be employed for a systemic or local effect. Bleeding from a vein or an artery, by diminishing the whole quantity of the circulating fluid, and by altering its quality, affects the functions of every organ, and especially of organs the seat of an acute hyperaemia. Cupping and leeching, if carried far enough, may diminish the general blood-pressure and the proportion of the morphotic elements; but their action is largely local and revulsive.

The effects of bloodletting on the composition of the blood are these: the water is increased and the globules, fibrin, and salts are diminished in relative amount; an artificial anaemia is thus induced. The action of the heart becomes more rapid and its force lessened; the arterial tension falls, and the pulse assumes the dicrotic character. The functions of organs, especially of the brain and nervous system, lose energy. Nausea, vomiting, faintness, syncope, and epileptoid seizures occur, when the loss of blood is considerable. Epileptiform convulsions is a constant phenomenon in animals bled to death (Kussmaul and Tenner).

When the quantity of fluid in the vessels is lessened by bleeding, thirst is experienced, and absorption is more rapid; the sensibility to pain is diminished, probably, because the perceptive centers are functionally inactive; and. the power to evolve force, muscular, digestive, nervous, etc., is greatly restricted. Only one function, therefore, is rendered more active by bleeding; all the others are depressed in consequence of the inadequate supply of nutrient material.

It is a remarkable fact, perfectly well known to old practitioners, and to which Sir James Paget has recently called attention, that the ill effects of bleeding, in healthy subjects, are very temporary and easily repaired. The blood-globules, which are relatively more affected by bleeding than the other constituents, are quickly reproduced, and the functions of organs suddenly very much depressed soon recover their normal energy. That any permanent injury is done to the healthy human system by a moderate bleeding seems, therefore, to be highly improbable.

Therapy

The limits of this work will not permit the introduction of any controversial discussions. The author is to be ranked with those who do not employ general bloodletting, but he does not deny that it is occasionally useful; and that, indeed, it may be indispensable. A summary of the physical conditions in which venesection may be useful or indispensable should not, therefore, be omitted from a work on therapeutics.

The therapeutical effect of a general bloodletting in congestion and inflammation is largely mechanical. In acute congestion of the lungs, when aeration of the blood is seriously impeded; when there are extensive stasis on the venous side, and ischaemia on the arterial side of the systemic circulation, great relief may be afforded by the abstraction of from four to sixteen ounces of blood. In the apoplectiform variety of acute cerebral congestion, damage to the brain may be prevented by letting blood. The effect of the bleeding is to diminish the intra-cranial pressure, and thus relieve the strain on the cerebral vessels. In eclampsia, especially of the puerperal variety, accompanied with the evidences of cerebral congestion, great relief may be procured by the timely abstraction of blood. The quantity of blood to be taken will depend in part on the character of the subject and on the amount of congestion.

The mechanical effect of the withdrawal of blood from the systemic circulation may be most advantageous in cases of sudden over-disten-tion of the right cavities of the heart.

Pulmonary haemorrhage, when dependent on acute congestion of the lungs, the general condition being one of plethora, may be promptly arrested by opening a vein in the arm.

The pain of acute pleuritis, and acute peritonitis, can be quickly relieved by bloodletting.

Although it is undeniable that the important results above mentioned may be obtained from general bleeding, it is equally certain that as good results in most of the conditions may be had by other methods. Acute diseases make such serious demands on the vital resources of patients, that the practitioner should seriously ponder the propriety of taking blood even in those cases to the relief of which it may seem to be adapted. Large bleedings, experience has abundantly shown, render the convalescence from acute diseases tedious—for the patient has to make up the losses by venesection as well as the ravages of the disease.