It must be acknowledged that a very different account of the effects of digitalis on the circulation has been given by some writers. Thus, Dr. James Sanders, of Edinburgh, who bases his statements upon the observations of 2000 cases, asserts that the first effect is almost instantaneously to increase the frequency and force of the pulse, which sometimes quickly subsides, sometimes continues excited for several days under the use of the medicine; though ultimately, in the course of a day or two after its exhibition, a reduction of the pulse may take place. (Treatise on Pulmonary Consumption, etc., Edin., 1808, p. 196-7.) No other writer, I believe, has gone so far in this direction as Dr. Sanders; but several others have maintained the primarily stimulant property of digitalis. The vast majority of observers, however, have failed to discover this effect; and, though I have employed the medicine in a very great number of cases, during a practice of more than forty years, I have rarely noticed any increased frequency of pulse, at any time, from the use of it. I do not deny that it may sometimes accelerate the pulse; but much more frequently, when any result of this kind is observed, it proceeds from some other cause wholly independent of the digitalis; and, when the effect of the medicine, is probably produced through the sympathy of the circulation with the primary irritant impression of the digitalis on the stomach. in the cases noticed by Sanders, the effect on the circulation so quickly followed the exhibition of the medicine, that absorption could not have taken place; and, whatever increase of pulse occurred, if proceeding from the medicine, must have been occasioned by a sympathetic impression extended to the heart, either from the mouth and fauces, or from the gastric mucous membrane. This view is confirmed by the experiments of MM. Bouley and Reynal on horses, already noticed. it has been stated above that, when the medicine was given to these animals in therapeutic doses, that is, in doses too small to irritate the stomach, it invariably reduced the pulse without any previous acceleration. But when a poisonous quantity was exhibited, some excitation both of the pulse and respiration took place, before the characteristic prostration, which preceded the fatal result. {Arch, de Physiol., Jan. 1854, p. 216, etc.) in these instances, the gastric inflammation produced by the large amount of the poison taken induced a general febrile condition, antecedent to the characteristic effects resulting from the absorption of the poison. But the strongest experimental proof of the depressing influence of digitalis on the circulation is that produced by Dr. Traube, of Berlin. in several instances the infusion of digitalis was injected into the jugular vein towards the heart; and invariably the pulse was rapidly and greatly reduced in frequency, in one instance falling, in a single minute, from 132 to 24. if, after the injection, the par vagum was cut on both sides, the pulse quickly rose to more than its original frequency; and if the division was made prior to the injection, little or no depression was produced; thus proving that the medicine had no immediate action upon the heart itself, but operated through the nervous centres in the medulla oblongata. But a singular fact was developed by a repetition of the injections successively, until a large quantity had been introduced. Thus, in the same animal in which the reduction above mentioned took place immediately after the first injection, upon its repetition several times, at intervals of a few minutes, the fifth was followed by an extraordinary frequency of the pulse, which rose to 174. By the large quantity, the nervous centre became paralyzed, and thus ceased to be able to transmit the depressing influence to the heart, which was now submissive to the direct stimulant action of the blood, increased by the locally irritant properties of the digitalis. Dr. Traube advances a somewhat different explanation of the results here stated; but they clearly admit of that which I have given, and confirm the view here taken of the direct sedative influence of digitalis on the circulation, through the nervous centre of this function in the encephalon. (See Lond. Med. Times and Gaz., April 21, 1855, p. 381.)

Not unfrequently, the first change in the pulse to be noticed is intermission, instead of a regular subsidence in frequency. This I have often observed; and I always regard irregularity of pulse, occurring after the exhibition of digitalis, unless traceable to some other obvious cause, as an evidence of the commencing action of the medicine upon the circulation.

In other cases, it is impossible to obtain from the medicine its legitimate action upon the pulse, unless pushed further than prudence would warrant. This may be owing to idiosyncrasy in the patient, or to the rapid passing off of the medicine by the kidneys as fast as it enters the circulation, or lastly to a tendency to irritate the stomach, so as in this way either to interfere with absorption, or to counteract by an indirect stimulation the direct sedative influence of the remedy.

It was noticed by Dr. Baildon, of Edinburgh, that the influence of digitalis upon the circulation was much affected by posture. The pulse which, in his own case, had, under the influence of the medicine, fallen from 110 to 40 in the recumbent position, was increased to 72 when he sat, and to 100 when he stood. (Ed, Med. and Surg. Journ., III. 270.) The following explanation of this phenomenon was given by me in the first edition of the U. S. Dispensatory, published in 1833. "it is well known that the pulse is always more frequent in the erect than in the horizontal posture, and the difference is greater in a state of debility than in health. Digitalis diminishes the frequency of pulsations of the heart by a directly debilitating power; and this very debility, when any exertion is made which calls for increased action in that organ, causes it to attempt, by an increase in the number of its contractions, to meet the demand which it is unable to supply by an increase of their force." This I still consider to be the true explanation, with the exception that the medicine should be stated as acting on the heart through its encephalic nervous centre, instead of immediately upon the organ. The result is in perfect accordance with the general views here given of the action of digitalis.