Again, if we withdraw a certain quantity of blood from the circulation by venesection, and call that amount d, we shall then have the formula
x = b / ( a - d )
But, if we wish to act upon the organs of the trunk, and more especially upon those contained within the cerebro-spinal canal, it is not necessary to resort to such a drastic expedient as copious blood-letting; for, in place of this, we may dam up and effectually eliminate from the rest of the body a certain amount of blood by passing a ligature around the central portion of one or several extremities, so as to interrupt the circulation in both artery and vein. When this has been done it is clear that we may introduce a remedy into the system by way of the stomach, or hypodermically into some portion of the trunk; and it is equally certain that a remedy so introduced will be diluted only in the ratio of the amount of blood freely circulating, and more especially by that contained within the trunk and head. That which is incarcerated behind the ligatures is as effectually withdrawn from the realm of physiological action as though it had been abstracted by the surgeon's knife. Elimination by the knife and elimination by the ligature are, for present purposes, then, one and the same thing. Hence, if we let d' represent the amount of blood incarcerated behind the ligatures, x the magnitude of the physiological effect which we are seeking, b the amount of remedy exhibited, and a the total amount of blood contained in the whole organism, we shall have the formula,
x = b / ( a - d' ) = b / ( a - d )
Several years since, I had an excellent opportunity of proving the truth of the foregoing, in connection with the administration of ether in the case of a patient who resisted all attempts to anæsthetize him in the ordinary way.
The case in question was a man under treatment at the Manhattan Eye and Ear Hospital, upon whom it was deemed advisable to perform an operation. As has been said, the ordinary means of inducing anæsthesia had proved ineffectual, for the man was a confirmed drunkard; and it was at this juncture that I was called in consultation and requested by my friend, Dr. David Webster, one of the surgeons of the hospital, to endeavor to devise some means of getting the man under the influence of the anæsthetic.
The procedure which I suggested was this:[2] Around the upper part of each thigh a flat rubber tourniquet was tightly drawn and secured in place in the usual manner. By this means the sequestration of all the blood contained in the lower limbs was accomplished; but, inasmuch as both artery and vein were compressed, only the amount of blood usually contained in each limb was shut off from the rest of the body—which would not have been the case had we contented ourselves with merely compressing the veins, as some have done.
In subsequently commenting on my published report of this case, that most accomplished writer and physician, Henry M. Lyman—than whom there is no greater authority on anæsthesia—observes that the plan proposed and adopted by me on this occasion (that of compressing both vein and artery) is far preferable to compression of the vein alone.
The reason for this is not far to seek. When we compress the veins alone there is a rapid accumulation of blood in the extremities through the accessions derived from the uninterrupted arteries. Now, as this blood is derived from the trunk, and consequently also from the organs contained within the cerebro-spinal canal, there is danger of syncope and even heart failure. When, on the other hand, both artery and vein are compressed no such derivative action occurs, and all danger is, consequently, removed. With an apology for this brief digression, I now return to the interesting case which has given rise to it.
Having, as previously stated, applied tourniquets to the central portion of the lower limbs, the ether cap was placed over the mouth and nose of the patient, and in an incredibly short time he was unconscious, and the surgeons were able to go on with the operation.