ON THE PRESENT CONDITION OF VASO-MOTOR PHYSIOLOGY. IN the Transactions of the American Medical Association for 1856, the privilege was accorded to the writer of publishing a paper upon the Arterial Circulation, in which views were expressed and maintained, somewhat at length, in partial opposition to the then prevailing opinions of physiologists. It was at that time the teaching especially of the Webers, Virchow, and Bernard (to whose names have been since added amongst others those of Huxley and Marey), that the whole and sole functional action of the smooth muscular tissue, so abundant in the smaller arteries, is to limit, by its contraction, the flow of blood through the vessels; called by Prof. Huxley a "flood-gate" and by others a stopcock function; so that, as Virchow has expressed it," the more active the vessel, the less the supply of blood." Opposed to this view have been the opinions of some of the older writers, as Unzer, Prochaska, John Hunter, and Sir Charles Bell; and against it, moreover, as it has appeared to the writer, is an overwhelmingly strong presumption, from the positive evidence of general physiological analogy. Slow as has been the progress of recent investigation upon this point, Prof. Lister, of Glasgow, made an important impression upon the general tendency of reasoning concerning it, in 1858; in a direction in part quite similar to that of the Essay already referred to, of 1856. Since 1868, however, a more decisive contribution has been made to the inquiry, by the elaborate experimental researches of Legros and Onimus; published in the Journal de l'Anatomie et de la Physiologie, 1868-70. Some, at least, of the writers, before inclined to deny that any ground existed for doubting accepted views on the subject, now admit that a revision of those views becomes necessary; and it appears to be hardly too soon to anticipate that, very shortly, a reversal of the common teaching of the last twenty-five years concerning arterial physiology will have to be made in all the books. Holding this opinion, I have thought it à propos, as a member of this Association, to lay claim, on behalf of its Transactions, for a certain part in the progress of this important inquiry, in the publication of the paper referred to, partially indorsed at the time by the award of the prize of the Association; in which, facts, reasonings, and conclusions were collated, in advance of all written upon the subject since the "Essay upon the Circulation" of Sir Charles Bell. I propose, in the paper now presented, to state, briefly and succinctly, the most essential links of the chain of argument by which, as it appears to me, a true conclusion upon the mode of action of the arteries may now be reached and sustained. A certain portion of this summary will be recapitulatory; as the time elapsing since my first publication is so considerable, and a later paper1 had a somewhat disadvantageous opportunity of presentation to the profession. But the recent establishment of some facts which appear to be of demonstrative force, has been the occasion of my requesting renewed attention to the question at this time. At the foundation of all study of the subject lies the universality of the law of alternating contraction in muscular fibre; first clearly shown by Bowman, many years ago, but more amply and elaborately established, within a few years, by Marey. Even in the most seemingly rigid tonic contraction, the latter experimenter was able to prove that it was not absolutely fixed, but rapidly vibratory, in every filament. All authorities agree, moreover, in finding this rhythmic character to prevail most evidently in the smooth or nonstriated muscle of organic life; the heart, however, among the striated muscles, affording its most typical instance. In the veins, rhythmic contraction has been noticed by Wallæus, Steno, Lower, Whytt, Haller, Lancisi, Senac, Broussais, Allison, Marshall Hall, Flourens, and Wharton Jones, under various circumstances. In the pancreatic duct and ductus choledochus, such alternating contractions have been observed by Bernard, and by Brown-Séquard in the trachea and bronchia of birds. We are warranted by these as well as by the more familiar example of intestinal peristalsis, in conceiving it to be a most strong presumption, that everywhere, even in the arterial system, the law of smooth muscular tissue must be, that its normal action will be alternating or rhythmic, its abnormal condition only, that of temporary tonic contraction or rigidity. 1 American Journal of Natural Sciences, July, 1868, p. 290; under "American Intelligence," etc. Certain facts in animals seem to make necessary this explanation. In fishes, for example, the heart is respiratory; its impulse being to a large extent expended in sending the blood through the gills; this must then find its way through the system mainly by arterial action. Amphioxus presents a sort of demonstration of this; as this fish has, instead of a true heart, a number of pulsatile dilatations of the great arterial and venous trunks; parallel to the enlargements, with similar function, in insects, myriapoda, and some other articulates. Allen Thomson remarks upon the difficulty of understanding how arterialized blood is distributed, in the whale, from the net-works of arteries connected with the intercostal and other vessels. This difficulty disappears when we perceive, in these arteries, a normally propulsive power. Acephalous foetuses afford evidence of an analogous kind. St. Hilaire, Chaussier, and Adelon aver that every acephalous foetus is acardiac, as well as having no lungs. The circulation must then be carried on by the arteries. Every human embryo is, for a certain time, as acardiac as that of a myriapod; so that in it, also, the circulation must be arterial and capillary only, so far as its propelling power is concerned. Erectile tissues present a problem only thus to be solved. Long ago, Müller discovered the arteriæ helicina of the penis; confirmed by Valentin and Kölliker. Earlier still Prochaska proposed the explanation that erection is caused by active arterial injection. The idea that a dilatation of the venous trabeculæ of the corpora cavernosa is an active cause of erection, is at once disproved by the absence of any such trabeculæ from the nipples, which also are truly erectile; and whose erectility, therefore, must be an active arterial phenomenon. Legros, in 1868, having proved the remarkable thickness and power of the muscular tissue of the arteries of erectile tissues, asserts "c'est bien l'élément contractile des artères qui agit pour produire l'érection." What can we make of the reddening, from increased vascularity of the skin, when struck with a switch or the hand (even a short time after death), or under the stimulus of friction, mustard, ammonia, or cantharides? Surely there is no "paralysis" of vasomotor nerves, or of arterial muscular tissue, under any such causation. If there be a pure stimulation anywhere of a reflex or excito-motor character, it is here. Nor, in blushing, have we a right to make the assumption, often made, that a paralytic dilataVOL. XXIII.—13 |