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the veins, which is almost continuous, as both the auricle and the ventricle alternately force their blood in this direction. The collapse, first of the veins next to the auricles and then of the auricles, consequent upon their sudden evacuation by the suction-power of the ventricles, has been mistaken for a contraction of the veins and auricles themselves. Nature has provided for a continuous flow of venous blood back to the heart proper, to the ventricle. Has she also provided for a force to subvert her own designs? Of all the phenomena attending the passage of the blood through the cavities of the heart, there is but one active force, the contraction of the ventricles. All the others are caused by this and are passive. Should not auricular contraction be dropped from our nomenclature? It is claimed by physiologists that the auricular contraction immediately precedes the ventricular, beginning when the auricle has within its walls but a trifling amount of blood, and that its contraction drives this blood into the ventricle. In addition to the reasons that have already been given against the theory of auricular contraction is this that can be assigned against auricular contraction thus beginning. All other hollow organs contract in health upon their contents, these serving as stimuli. Here the walls only begin their contraction after their contents have been nearly discharged.

In order to measure the cavities of the heart, and for the purpose of ascertaining the relative size of its inlets and outlets, as well as for the purpose of bringing into view the thickness of the auricles and veins, and more particularly the thickness of the auricular appendages, etc., I took plaster casts of all these parts. I found it a very easy task. Going to a slaughter-house, I procured from several bullocks the hearts with the lungs attached, and, while these were yet warm, I poured the plaster prepared for the occasion into these cavities, through an ordinary funnel or a horse-syringe. The plaster was poured into the cavity in some instances through the veins, and in some through the arteries, according to the cast desired. Among the precautions to be used in taking these casts, are the following: The cavity should not be opened by the knife. In case of the auricle this will require care. The

heart should be removed from the lung by cutting close to the heart through the lung-tissue. These sections should be made immediately after the lungs and heart have been removed from the animal. The cavities should be rinsed out thoroughly, by means of a syringe and warm water, in a warm room. In case of the auricle, all the points of entrance should be closed by means of a needle and thread, except the one admitting the plaster; and this should be fastened tightly around the nozzle of the funnel or syringe. In case of the ventricle, the plaster should be introduced through the artery, the semi-lunar valves having been removed. Considerable force should be used in filling this cavity, the horse-syringe fulfilling the purpose well. While the heart is being filled with the plaster, it should be held up by an assistant; and afterward it should be suspended in a dry, warm room until the following day, when the plaster will be found sufficiently hard to allow of the removal of the walls by means of a knife and the fingers. In case of the auricles, the translucent covering over the plaster cast of that part termed the appendix should be removed only in part. After a few days, these casts will become firm and hard. I have in my possession a plaster cast of the right auricle, the terminations of the ascending and descending venæ cavæ, and the auricular appendix. The thickness of the covering to the part called the auricular appendix is no more than that of ordinary writing-paper, and this is as distinctly muscular as any portion of the auricular walls. The mere appearance of this covering, considered in connection with its relations to other parts, is sufficient to demonstrate conclusively, to any unprejudiced mind, that it is not intended to constitute any portion of the walls of a contracting organ. This cast also shows that the outlet from the auricle into the ventricle is about four times greater than the outlet from the ventricle into the pulmonary artery.

Both Goltz and Gaule have demonstrated that there is a considerable suction-force exerted by both ventricles at the time of their diastole. Fick, by the use of the manometer, had previously demonstrated the same fact, while he found, by the use of

this instrument, that the blood-pressure at the mouths of the great veins and in the right auricle was at all times nearly constant; and he believed that the proper function of the auricles was to equalize and keep constant the pressure at the entrance of the great veins into the heart. I have made a large number of experiments upon dogs, for the purpose of ascertaining if there were at any time any such thing as contraction on the part of the auricles. While the heart was acting vigorously, I have penetrated the auricle with all kinds of trocars and canulas, large and small, long and short, and at different sites; and I have failed in every instance to get a jet of blood through a canula, the trocar being withdrawn.

In the case of specimen Number 1536, the auricle being enlarged to the size of a man's fist and as thin as ordinary paper, no one will claim that the ventricle was filled by the contraction of such an auricle; and yet the ventricle must have obtained its blood through an inlet of less than one quarter the size of that through which it is usually filled. In this very case, if the ventricle can obtain its blood by its own action, why not in a normal state, in which the supply comes to it through an opening more than four times as large? Everything goes to show that there is in the auricle no fitful or periodic pressure upon the blood, but the opposite, a steady and equable one. The contraction which begins in the veins and extends through the auricles, in my opinion, was never seen or felt; and it exists only in the ready imagination of observers who are willing to declare a thing to be true which is a necessity to the demonstration of their theories. When the chest of an animal is open and the heart is well exposed, it is difficult to decide which of its motions corresponds to the contraction of the ventricle, and which to its dilation, and Dalton settles this question by the use of the canula. What must be said, then, of the auricle? No structure, not even the veins. themselves, is more elastic than the auricles and their appendices. They are easily distended, and, as the force is removed, they readily retract. Like the rubber cushion, they are always in contact with their contents, great or small. All this can readily be demonstrated by introducing warm water by means

of a syringe and then letting it out. The systole, the contraction of the auricle, is said to begin in the veins. Even if this were so, if any such observation had ever been made, it could be explained by the rapid removal of the blood from these parts into the ventricle; as these are the conditions in which the sudden evacuation of the blood would produce collapse.

The muscular tissue in the auricles has been sufficient to bias the minds of many in favor of the theory of their contraction; and because, like the ventricles, they contain striated muscular fibres, they are supposed, like the ventricles, to contract. The walls of these two cavities are affected very differently by distention; those of the ventricle giving way or breaking under any force sufficient to enlarge the cavity. In fact, the capacity of the ventricle is about as fixed and definite as that of a chinacup or glass-goblet. Not so with the auricles. Their cavities and their walls adapt themselves to little or much force. Their walls, like those of the rubber cushion, are easily distended; and, as the distending body, water, blood, or any liquid, is removed, they readily retract.

DISCUSSION.

DR. AUSTIN FLINT, JR., of New York County. It is difficult to discuss extemporaneously a paper the contents of which one is not perfectly familiar with ; but I infer, from what I have heard of Dr. Lynde's paper, that it embodies views which are entirely opposed to the generally-accepted doctrines of physiologists concerning the functions of the auricles. I can not indorse the statement made by the author of the paper, that the auricles did not contract; and I beg to state some of the reasons for my belief, as they occur to me at the moment.

In the first place, I have repeatedly seen the auricles contract in experiments on the lower animals. Of course no opportunity has occurred for observing their contraction in the human subject. Again, the auricles, although possessing much thinner walls than the ventricles, are composed of muscular fibres of the striat

ed variety, or closely resembling striated muscular fibres. It is well known that, if a muscle be prevented from contraction by having its motor nerve divided, or by being restrained by a splint, it will undergo fatty degeneration and atrophy. No such appearance is observed in the muscular walls of the auricles, the muscular fibres here having the same structure as those found in the ventricles, which are known to contract at stated intervals.

The arrangement of the fibres around the openings of the veins into the auricles is such that, although not provided in man, as in fishes and certain other of the lower animals, with valves, a certain degree of constriction takes place, diminishing the lumen of the veins sufficiently to prevent any considerable regurgitation of blood during the auricular contraction, thus causing nearly or quite all the liquid to enter the ventricles.

Experiments made upon the hearts of dogs, which resemble in structure the heart of man, show, not only that the auricles contract, but observations have determined the duration of the period of contraction. Marey experimented upon dogs, by introducing a hollow sound, provided with two small rubber bags, through the jugular vein into the heart, one of the bags resting in the ventricle and the other in the auricle, and each being connected with a registering apparatus. By this experiment, Marey was able to show that the contraction of the auricles occupies about two tenths of the duration of one revolution of the heart; contraction of the ventricle occupying about four tenths of the period; the remaining four tenths being taken up by the general diastole. These reasons long since led me to the opinion, entertained by nearly all physiologists, that the auricles, although their walls are thinner and less powerful than those of the ventricles, contract, and that they contract as regularly as do the ventricles. The contraction of the auricles, however, is far less important than that of the ventricles, as is shown by the fact that their contractile power may be completely exhausted by repeated stimulation with the electric current, and yet the circulation in the general system continue, although it is somewhat weakened.

Dr. Lynde has spoken of a suction-force exerted by the ventricles. It is possible to demonstrate by experiment either the presence or the absence of any such suction-force. A hollow sound may be introduced through the jugular vein into the right ventri

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