powers of the the sanguineous sys tem. dred pulsations in a minute, while not more than seventy II. Moving strokes may be exhibited in any other part of the system. The rapidity of the pulse is in this case usually in proportion to the degree of the inflammatory action *: and hence, if the system should labour at the same time under ten different inflammations in different parts or organs of a different structure, as glands, muscles, and membranes, it is possible that it may have so many dif ferent seats of pulsation taking place at such different parts at one and the same time, while all of them are at variance with the pulsation of the heart. Even where there is no inflammation such discrepancies in the pulse are occasionally to be met with, insomuch that Reil gives a case in which the heart, the carotids, and the radial arteries all pulsated differently +: and we can hence readily perceive why they should be more frequent and striking under the increased action produced by inflammation, and often, in a debilitated organ, more disposed to irregular action and particularly irregular contractile action in its capillaries. possess more con than the larger We are, indeed, let a little into the mystery of this pha- Capillaries nomenon by the curious fact that some of the arteries possess a higher degree of contractile power than others, tractibility and that the capillaries possess the highest measure allotted to any of them. "Indeed every fact", observes Dr. Bos- arteries. tock, "with which we are acquainted respecting the me- Confirmed chanism and functions of the sanguiferous system, lead by Bostock. us to the same conclusion, that the large arteries are to be regarded as canals transmitting the blood from the heart, where it receives its great impulse, into the smaller branches; and that it is chiefly in these smaller branches that it exercises its various functions." We may hence Important see why the capillaries are, in many cases, so much excited than the larger canals, and exhibit so much more flammation. sooner • Exposition of the Principles of Pathology, &c. By Daniel Pring, M.D. p. 119. 8vo. 1823. + Memorabilia Clinica. Vol. 11. Fascic. 1-6. Hall. 1792. Elementary System of Physiology. Vol. 1. p. 402. 8vo. 1824. . effect of this fact on in powers of II. Moving violence of action: a distinction of high importance in explaining the doctrine of inflammation, though it has neous sys- been less attended to by pathologists than it deserves. the sangui tem. Hence the hypothesis of a vis à tergo un whence soever derived. Further The hypothesis, therefore, of a vis à tergo, whether dependent upon the heart alone, upon the arteries alone, or upon a combination of the two, has by no means satisfactory, proved sufficiently satisfactory, or been sufficiently supported by evidence in respect to the entire circulation. Under no modification does it account for the flow of the blood through the veins. And in regard to the whole of the views which have been thus far examined, Mr. John Hunter, as I have already observed, was so extremely discontented that he placed no more stress upon one part or organ of the sanguiferous system than upon another; upon the heart than upon the arteries; or upon the arteries than upon the veins; regarding the whole economy as the result of a sort of instinct, to which, as just noticed, he gave the name of a stimulus of necessity; and which opinion he supported by making an appeal to insects which have no proper heart; to worms, most of which have no heart whatever; and to monsters which have been born without a heart; whilst at the same time he contended that veins, at least the larger, exhibit, under certain circumstances, an expansile and contractile power as well as arteries. "I think it probable", says he, "that where there is an universal action of the vascular system, the action of the arteries and veins is alternate: that where the arteries contract, as in many fevers, the veins rather dilate, more especially the larger.' And it is hence, again, highly probable that in this "universal action of the vascular system" the secernents or extreme arteries take an important part, and, as has since been suggested by Dr. Pringt, operate by a kind of suction, which may be regarded as a vis à fronte. Action of secernents. Upon the whole we may conclude with Haller, that the heart exerts a very considerable degree of force in the general economy of the circulation, although it is impossible to estimate its power with mathematical precision. And we may reasonably refer the first, or arterial half of the general circuit of the blood to this force, if not alone, in conjunction with the aid contributed by the elastic and contractile tunics of the arteries themselves, whether pulsation be a result of these powers alternately exercised, or of mere local pressure. II. Moving powers of neous sys the sangui tem. Moving power of arterial cir culation. Moving power of culation. venous cir Vacuum in produced by its sys the heart It yet remains, however, to account for the second half, or that which consists in the passage of the blood through the veins; and upon this subject there is one most important and elucidating fact, which, till of late, has never been in any degree brought forward in the course of the inquiry. It is this: that when the heart, by the contraction of its ventricles, has exhausted itself of the blood contained within it, a comparative vacuum must follow, and the blood from the venæ cavæ, or venous system at large, be sucked up into the right auricle. This ingenious remark seems first to have been thrown out by Dr. Wilson: and Dr. Carson of Liverpool, taking advantage of it, has constructed a simple and beautiful theory of the projectile powers employed in the circulation, the general principle of which may be expressed in a few words. The heart is supposed to act at one and the General cirsame time in a two-fold capacity. By the contraction of culation the ventricles, it propels the blood through the arteries; the double and by the dilatation of the auricles, it draws it up from the veins. It is at once, therefore, a forcing and a suc tole. produced by power of the heart acting as a forcing and suction pump: tion pump. The contraction of the heart, and consequently its comparative vacuum, are supposed to be con- assisted by siderably assisted by the elasticity of the lungs, and the surrounding play of the diaphragm, which we had occasion to notice agency. at some length in our physiological proem to the preceding class, and the great resistance which they jointly afford to the atmospheric pressure; whilst this very pressure, applied on every part of the exterior of the animal frame, contributes in an equal degree to the ascent of the blood in the veins; for, as the column of ve • Wilson's Enquiry, &c. pp. 9. 11, 16. &c. powers of II. Moving nous blood is perpetually girt on all sides, and cannot fall back because of the numerous valves with which the veins are furnished, it must necessarily take an opposite or ascending direction. the sanguineous system. Difficulties still remaining to be explained. Communication be. tween re distinct from that of the blood. spleen and stomach. There are, nevertheless, numerous difficulties that yet remain to be explained; such as the proportion of projectile power furnished by the conducting pipes themselves; by what means the want of a diaphragm is compensated in birds and reptiles which have no such organ; and what constitutes the projectile power in animals that have no heart, and consequently no double pump to work with. There is also another curious fact which physiology has pointed out, but has never hitherto been able to exmote organs plain: and that is, a direct communication between remote or unconnected organs, apparently, by some other channel than the circulation of the blood. Something Between the of this kind seems to exist between the spleen and the stomach, the former of which has been proved by Sir Everard Home to receive fluids from the cardiac portion of the latter, though we can trace no intercourse of vessels: but the most extraordinary example of this kind which at present we seem to possess, is the communicaBetween the tion which exists between the stomach and the bladder. For the experiments of Sir Everard Home+, and the still more decisive ones of Dr. Wollaston and Dr. Marcet‡, seem to have established, beyond a controversy, that certain substances introduced into the stomach, as rhubarb or prussiate of pot-ash, may pass into the bladder without taking the course of the blood-vessels, and consequently by some other channel; a channel, indeed, This subject of which we know nothing. This is a subject well worth further in- studying: for if two organs so remotely situated as the stomach and the bladder be thus capable of maintaining a peculiar intercourse; so other organs may possess a like stomach and bladder. entitled to quiry. Diatribe Anatomico-Physiologica de Structurâ atque Vitâ Venarum; à Medicorum ordine Heidelburgensi præmio proposito ornata. Auctore Henrico Marx. 8vo. Carlsrue 1822. intercommunion; and by such means lay a foundation for II. Moving those numerous sympathies between distant parts which powers of the sanguiso often strike and astonish us. M. Magendie's hypo- neous systhesis that veins are absorbents will explain the facts in tem. Sir Everard Home's experiments, but has no bearing upon that of Dr. Wollaston and Dr. Marcet. Doctrine of pulsation, and its im The discovery of the circulation of the blood has given a great importance to the DOCTRINE OF PULSATION; for by the strength or weakness, the slowness or frequency, portance. the hardness or softness, the freedom or oppression, the regularity or irregularity of the beat of the artery against the pressure of the finger, we are now able to determine many momentous facts, relative, not merely to the state of the heart, but of the general system; and, in many cases, to prognosticate upon grounds which were altogegether unknown to the earlier cultivators of medicine. And on this account it is that the Greek physicians took but little notice of the pulse, which, even in the days of Celsus, was regarded as a res fallacissima. influenced. The pulse is influenced indirectly by the general state Pulse how of the body, but directly by that of the heart, or of the arteries, or of both, or of the quantity of blood which the vessels have to contain. adult life. ment and In an adult male of good health, and not too corpu- Standard in lent, the common standard of the pulse may be fixed at seventy strokes in a minute: but it varies in different individuals from sixty to eighty, being greatly affected by Influenced the temperament, and partly by the habit of life. In the by temperaman of a high sanguine character it rarely sinks below idiosyncraeighty, and is often at ninety; and in the melancholic it sies. seldom rises above sixty, and sometimes sinks to forty. In some idiosyncrasies the discrepancy is so considerable, and complicated with other changes than those of frequency and tardiness, that there is no reducing them to any rule. Lizzari tells us of a person whose pulse was not more Singular inthan ten beats in a minute *. Dr. Heberden says, he once saw a person whose pulse, as he was told, did not num Raccolta d'Opusculi Scientifici, p. 265. stances. |