3. Inflammation always commences with a more or less intense pain; the sensibility of the part is increased, redness soon follows, and blood appears in vessels where previously it had not been observed; the temperature of the part is raised, its functions disturbed, secretion suppressed, (at least at first,) or changed, perspiration diminished, and the part swelled. These appearances are developed, in different proportions, to a higher degree, in which fever (Febris inflammatoria secunda) usually becomes

connected with them.

[I apprehend it would be more correct to say that "inflammation, from its very commencement, is always accompanied with a more or less intense pain," than to say, with our author, it" always commences with a more or less intense pain;" inasmuch as, though that by which the patient's attention is first excited, yet it is only an indication of a disturbance set up in the economy, and which, as it becomes greater, renders itself apparent to the eye, most commonly by redness.-J. F. S.

Dr. ALISON (a) observes:-" In order to give the requisite precision to the general notion of inflammation as a local change of the condition of any part of the body, it seems only necessary to include in it, besides the pain, swelling, heat, and redness, the tendency always observed, even when the changes in question are of short duration, to effusion from the blood-vessels of some new products; speedily assuming in most instances the form either of coagulable lymph or of purulent matter." (vol. i. p. 53.)]

4. The pain depends on the increased activity of the nerves (1), and this again produces the succeeding increased influx of the blood, and the vital expansion of the vessels (2); afterwards the pain is increased by the decided expansion and tension which the part suffers. It differs according to the degree of inflammation and the sensibility of the affected part: often it consists only in the sensation of prickling, itching, tickling, and a troublesome stretching; often is it stabbing, tearing, burning, and, in structures largely supplied with nerves, it attains a most vehement degree (3).

The redness, heat, and swelling, depend on the increased action of the nerves and capillary vessels, and is in immediate relation with the richness of their ramifications. Hence the various degrees of redness, heat, and swelling, according to the degree of inflammation and the organs therewith affected. At the onset of the inflammation the swelling always depends on an increase of blood. The reddening of the blood (4) and evolution of warmth are attributes of the living process: they must, therefore, be also increased by its greater activity. According, however, to experiments with the thermometer, the warmth in inflamed parts is not so considerable as to our touch it seems to be (5). Where the most delicate branches of the capillary-vascular system anastomose to form the transition into the veins, several capillary vessels always open together into one single vein. By this disposition of the capillary-vascular system there is already in the healthy state a slower motion of the blood, which is in close relation to the functions of the capillary-vascular system. If, then, in inflammation there be an additional influx of blood, there must arise with the increased activity of the capillary-vascular system and vital expansion (6) an accumulation of it, (the blood,) as the veins are not in a condition to take up and carry away with equal readiness the blood which is brought to them in excess. The capillary vessels become therefore expanded, as if filled by artificial injection, and even distinct in those parts where we assume that in the natural state vessels carrying only the uncoloured part of the blood exist in the subsequent course of the inflammation new vascular branches are formed. The cellular tissue is the most especial seat of the development of vessels. These occurrences are the cause why (a) Library of Medicine.

the inflammation, which at first was to be considered merely as a dynamic disease, brings about distinct changes in the structure of organs. The increased activity of the nerves and capillary-vascular system produces a more copious infiltration into the cellular tissue than in the natural state; a part of the serum-in some cases even of the red part of the bloodpenetrates through the expanded walls of the vessels, and empties itself into the cellular tissue. The walls of the cells are, therefore, in this case, found thickened, filled with a serous, albuminous, often bloody fluid, in which frequently albuminous flakes float or are connected with the walls of the cells. The changed condition and increased plasticity of the blood is shown by the crusta inflammatoria, which consists of the fibrin of the blood. According to the different degree of irritation, and the consequent reaction of the nervous system, so long as, excepting the pain, no other appearance of inflammation exists, (which condition many consider as the forerunner of inflammation,) there is produced a spasmodic contraction with accelerated motion of the blood in the small vessels, upon which first follow their vital expansion, the greater influx of blood, and the other phenomena of increased living actions (7). A comparison may therefore be instituted between these local appearances and those coming in with inflammatory fever. As we have there contractions of the vessels and obstruction of the circulation, so we have here chilliness, contraction of the skin, small pulse, which are followed by the phenomena of vital expansion of the vascular system, increased warmth, and so on. In the commencement there is in a manner present an inflammatory spasm-the vascular system is entirely controlled by the nervous system. With the increased influx of the blood, and its accumulation in the capillary vessels, is the previously quickened motion of the blood corpuscles retarded, the capillary vessels, by the consequent exudation of the serum, become completely filled with blood-corpuscles, and an actual stagnation, an inflammatory stasis ensues, but which is not to be considered as a passive over-filling. [(1) But what causes this increased action of the nerves? The squeezing and stretching of the minute nerves of the part, by the increased size of the capillary vessels, resulting from the obstruction of the current of blood through them, which occurs at the very onset, and which, indeed, is, as will be presently shown, the first step of the inflammatory process. TRAVERS (a) considers "the pain of inflammation directly or indirectly connected with the state of the blood-vessels," and it is, "probably, the nerves of the bloodvessels that are first excited in the pain of inflammation." (pp. 46, 7.) This opinion is corroborated by referring to JOHN HUNTER'S observations on the passage of the adhesive to the suppurative inflammation, in which he says, "The pain is increased at the time of the dilating of the arteries, which gives the sensation called throbbing, in which every one can count his own pulse, from paying attention merely to the inflamed part; and perhaps this last symptom is one of the best characteristics of this species of inflammation." (p. 378.) And in a previous passage he had observed:-" Whether this pain arises from the distension of the artery by the force of the heart, or whether it arises from the action of distension from the force of the artery itself, is not easily determined." (p. 287.) The throbbing, however, is not entirely confined to suppurative, but also accompanies acute, inflammation; and TRAVERS has well observed: Throbbing, lancinating or pulsatile pain,-i. e. pain accompanied with a sense of motion of the fluids in the part,—is the most characteristic distinction of acute inflammation; and an obtuse, aching, or heavy pain belongs to a congested state of the local circulation." And he also points out that "the description of pain unattended with inflammation, differs from the pain of inflammation, although the former is subject also to varieties in kind, duration and intensity;" observing that “ Neuralgia is generally attended more or less with muscular cramp or spasm, and such pain is either intermitting or periodical;" and that such medicaments" as relieve pain in the absence of inflammation have little or no beneficial effect on the pain of inflammation. Blood-letting aggravates neuralgia and relieves inflammatory pain. Steel and arsenic aggravate inflammatory pain, and cure neuralgia." (pp. 45,6.)

(2) According to his neuropathological theory, HENLE (b) asserts, that "it is through the nervous system that the exciting cause of inflammation operates, by suspending the (a) Physiology of Inflammation.

(6) I have made use of the Digest of this Author's Pathologische Untersuchungen, 1840, and of his Bericht über die Arbeiten im Gebiet der

rationellen Pathologie seit Anfang des Jahres, 1839; in WHARTON JONES's excellent Report on the Theory of Inflammation, in FORBES's Brit and For. Med. Review, vol. xvii., 1844.-(J. F. S.)

nervous influence from the small vessels, and consequently determining relaxation of their walls with dilatation of their calibre." (p. 578.) The mode of action of the exciting cause he describes as follows:-"The exciting cause, of what nature soever it may be, whether external or internal, acts primarily on sensitive nerves, exalting their activity. The motor nerves of the vessels which have sympathetical relations with the excited sensitive nerves, are secondarily affected. But this affection of the motor nerves of the vessels, which supervenes by reflex action on the excitement of the sensitive nerves, is not a corresponding state of excitement, but an opposite one of depression, of suspension of action, of paralysis. This form of sympathy, on which the state of excitement of one nerve determines depression of another, HENLE calls antagonism ; when to that in which a state of activity of one nerve is called forth by a corresponding state of another, he applies the term sympathy in a more restricted sense than generally employed: the latter form is more common in the domain of the cerebrospinal system; the former in that of the ganglionic system, the source of the nerves of the vessels. Sometimes, however, sympathy is exemplified in the vessels by constriction supervening on irritation and preceding dilatation; but, in most cases, relaxation and dilatation of the vessels from suspension of nervous influence, are the primary effect of the irritation, no matter whether that irritation have been violent or moderate. Hence HENLE Contends that the relaxation of the vessels, on which their dilatation depends, cannot be a mere consequence of exhaustion of the vessels from previous action, as suggested by ALISON and BILLING, but can only be antagonistic." (p. 582.)

As to the cause of inflammation, HUNTER observes:-"I will venture to say, that any cause which can obstruct the motion of the blood for a given time, will become the cause of inflammation; for, either the cause of the obstruction itself, or the blood being retained in the smaller vessels for a certain time, will either irritate or unite the parts, or, where it irritates, will throw the vessels into such actions as naturally arise out of an extraneous irritating cause, but not an increased motion of the blood behind, to drive on the obstructed blood through these vessels, as has been supposed." (p. 259.) The truth of these views is fully borne out by the observations of more recent inquiries, some of which will be presently detailed.

(3) In reference to the pain in inflammation, HUNTER also notices that, as "Many parts of the body in a natural state give peculiar sensations when impressed: so when they are injured they give likewise pain peculiar to themselves;" of which the pain caused by squeezing or inflammation of the testicle is a good example. And I may also observe," he says, " that the same mode of impression shall give a peculiar sensation to one part, while it shall give pain to another: thus, what will produce sickness in the stomach, will produce pain in the colon." (pp. 288, 9.)

TRAVERS makes a remark shewing that pain is not necessarily an attendant on inflammation, which is well worth remembrance, and with which few careful observers will not accord. "We are told," says he, "there can be no inflammation where there is no pain. I reply, that there are many, and destructive too; a joint, an eye, nay, the lungs may be destroyed by inflammation without pain; he is a speculative, not a practical, pathologist who does not know this. It would be easy to superinduce pain in either of these cases; but let there be no interference, and the work of destruction in numberless cases is as silent as it is sure." (p. 29.)

(4) Touching the redness, HUNTER observes:-"It is of various hues, according to the nature of the inflammation: if healthy, it is a pale red; if less healthy, the colour will be darker, more of a purple, and so on, till it shall be a bluish purple; *** it is gradually lost in the surrounding part if the inflammation is of the healthy kind; but, in many others it has a determined edge, as in the true erysipelatous, and in some specific diseases, as in the small-pox."***"This increase of red appears to arise from two causes: the first is a dilatation of the vessels, whereby a greater quantity of blood is allowed to pass into those vessels which only admitted serum or lymph before; the second is owing probably to new vessels being set up in the extravasated uniting coagluating lymph." (pp. 283, 4.)

TRAVERS thinks that the intensity of the redness depends "on the degree of fulness (of the vessels) compatible with motion; for, although the oxygen of the atmosphere will redden the blood in the congested vessels of the surface, while circulation, however imperfect, continues, from the commencement of the state of absolute stagnation, the colour gradually undergoes a change from pink to purple. In some modes of inflammation this shade of colour prevails even from the beginning, and soon turns to livid. ***These varieties are due to the state of the general circulation, which gives its character to the inflammation, and an attending change in the constitution of the blood." (p. 50.)

an in

(5) JOHN HUNTER observes on this point:-" From all the observations and experiments I have made, I do not find that a local inflammation can increase the local heat above the natural heat of the animal." The experiments he made were, 1. in the inflamed cavities of hydroceles, in which the thermometer stood at 984° F., crease ended of 63 on the natural heat ascertained prior to the inflammation; but, as HUNTER states, " not equal to that of the blood probably at the source of circulation in the same man:" 2. in a wound of a dog's chest, in which before and after inflammation the heat was 101°: 3. in a wound in the gluteal muscles of an ass 100° before, and varying from 99° to 101° after inflammation: 4. in the vagina of an ass from 994, as before the inflammation to 1004. In other experiments on mucous surfaces the heat was sometimes the same as before the inflammation, and sometimes increased 1o or 2o.” (p. 293 to 300.) “ But,” as says TRAVERS," the nerves measure the sensation rather than the degree of heat, and this is a widely different scale from those of Fahrenheit or Réaumur,*** this determination of blood to the capillaries in blushing is accompanied with a distinct though transient sensation of burning heat to the individual, yet not such as could be ascertained by the most delicate thermometer. It is most probably to be referred to the extraordinary inlet of arterial blood into the capillaries: its longer detention by the congestion proper to inflammation, and the consequent increase and vigour of the neighbouring circulation would give permanency to the sensation, and render the actual increase of temperature appreciable.” (pp. 48, 9.) (6) In reference to the enlargement of the vessels of an inflamed part, and its visiblyincreased vascularity, HUNTER observes, that," instead of an increased attraction, there was rather what would appear an increased relaxation, of their muscular powers, being, as we might suppose, left to the elasticity entirely. This would be reducing them to a state of paralysis simply: but the power of muscular contraction would seem to give way to inflammation; for they certainly dilate more in inflammation than the elastic power would allow and it must also be supposed that the elastic power of the artery must be dilated in the same proportion." And he comes to the conclusion, "When we consider the whole of this as a necessary operation of nature, we must suppose it something more than, simply, a common relaxation: we must suppose it an action in the parts to produce increase of size, to answer particular purposes; and this I should call the action of dilatation." (p. 282.)

(7) This is pretty nearly the opinion of Dr. CULLEN, who taught that spasm of the extreme arteries supporting an increased action in the course of them, may be considered as the proximate cause of inflammation, at least in all cases not arising from direct stimuli applied; and, even in this case, the stimuli may be supposed to produce a spasm of the extreme vessels.

The following is a brief account of Dr. JOHN THOMSON'S (a) observations on the variation of the current of the blood through the capillaries, resulting from the application of different substances:-" Weak and strong spirits of wine were applied to the smallest arteries of the web in eight or nine different frogs, but without being able to perceive any sensible change in the diameters of the arteries to which the spirits were immediately applied, though the general circulation through the web seemed to be increased by each application of the spirits. The results were the same when the fincture of opium was employed." Weak volatile alkali, or ammonia, produced "a complete contraction in the arteries to which it was more immediately applied. In upwards of one hundred experiments the contraction produced took place in less than two minutes after the application of the ammonia. In thirteen experiments contraction did not take place till after a period of three minutes. In three or four instances only, in which the ammonia was applied, were the contractions not induced." (p. 83.) In some instances I thought I could perceive an increase of the velocity of the general circulation immediately after the application of the ammonia; in others, this increase, if it took place, was so small as to be imperceptible: but the first and most remarkable visible effect of the contraction of the artery from the application of ammonia was a diminution of the velocity of the circulation in the capillary vessels with which the contracting artery communicates. When the contraction is complete, a temporary stagnation in the capillaries with which the contracted artery immediately communicates is often produced. In all these experiments, in which ammonia alone was applied, a paleness rather than redness of the web in the foot of the frog was produced; but this paleness was only of short duration." (p. 84.) "In applying a saturated solution of common salt to the arteries in the web of the frog's foot, I was not a little surprised to observe that these arteries, instead of being contracted as they had uniformly been by the application of the ammonia, were actually and sensibly

(a) Lectures on Inflammation.

dilated. The part of the web to which the salt was applied became of a red colour, and this redness, which was visible to the naked eye, lasted in general from a period of three to five or more minutes. It was impossible to view the part with the naked eye, without conceiving it to be inflamed." THOMSON hoped, from "the facility of produ cing, by the application of salt, a state so accurately resembling inflammation that, by examining the phenomena of the circulation in this state, he should be able to arrive at some satisfactory conclusions with respect to the comparative velocity of the blood in healthy and in inflamed vessels; but he did not upon trial find this so very easy as he had at first imagined. (p. 85.) "The principal difficulty in ascertaining the comparative velocity of the blood in the sound and in the red or apparently inflamed parts arose from the very variable results which the application of salt produced in different animals, and in the same animal, in different circumstances." Thus, in nine cases, "the application of the salt was not only followed by a bright red colour visible to the naked eye, and a sensible enlargement of the arterial and venous branches, but with an increased rapidity of circulation also in the capillary vessels. * * * The repeated application, however, of the salt to the same vessels was always sooner or later followed by retarded capillary circulation, or even by complete stagnation. A second general result from the application of the salt was an apparent increase of circulation in the arteries and veins, with a diminution of velocity in the capillary branches. ** In no one experiment have I been able to perceive any enlargement of an artery during the momentary influx of blood into its canal. The third and most frequent result from the application of salt was diminished rapidity of circulation in arteries, veins, and capillaries. In seventeen experiments the circulation became so slow as to stop altogether in the capillaries, and this stagnation, which usually goes off in a few minutes, continued in some instances for several hours. The enlargement of diameter in arteries, veins, and capillaries is very conspicuous: they may be said to be distended. every experiment with salt, whether the velocity of the circulation was increased, diminished, or stopped, the diameters of the blood vessels were uniformly enlarged, and this increase of diameter continued till the redness spontaneously disappeared." (pp. 86, 7.) From these observations THOMSON comes to the conclusion, that, "If this view of the state of the circulation in inflamed vessels be just, it will follow that inflammation is sometimes attended by an increased, and at others by a diminished velocity in the circulation through the capillary vessels of the inflamed part, and, consequently, that neither of those two states ought to be included in the definition which we give of inflammation." (p. 88.) These experiments and conclusion of Dr. THOMSON are mentioned, because they are the first by which the condition of the vessels and the state of the circulation under inflammation have been attempted to be explained: but they are inconclusive; for, as observed by J. W. EARLE (a)," although that state of parts which was induced by the application of salt, viz. retardation and stagnation of the blood, presented the strongest resemblance to inflammation, yet in no one instance did either state continue for a sufficient length of time to allow any one of the usual accompaniments of inflammation (to wit, the effusion of lymph or pus, or mortification) to be produced, since each variation terminated more or less speedily in the restoration of the natural current." (p. 40.)

* In

Dr. W. PHILIP (b) applied "to the web of a frog's foot, placed under a microscope, distilled spirits, and in a few seconds observed the blood in all the vessels moved with a greatly increased velocity, which, as he constantly kept the web wet with the distilled spirits, continued as long as he observed it, ten minutes or a quarter of an hour; but during no part of the time could he perceive the slightest symptom of inflammation, either with or without the microscope. The vessels, instead of appearing redder and more turgid, were evidently paler and smaller than before the application of the spirits." (p. 30.) Hence it appears that his experiment does not in its result tally with THOMSON'S, who at first did not observe any increased velocity, nor ever any sensible change in the diameter of the arteries. It is probable that in neither case did the spirit operate beyond constricting the parts by the cold its evaporation produced. In another experiment, however, inflammation was produced in the web of a frog's foot, and then Dr. W. PHILIP (c) “ found the vessels of the part greatly dilated and the motion of the blood extremely languid. In several places where the inflammation was greatest, the vessels were most distended and the motions of the blood were slowest." (p. 15.) He therefore considered that in inflammation the blood vessels were in a state of debility.

66

(a) On the Nature of Inflammation, &c.

An Experimental Inquiry into the Laws of the Vital Functions. London, 1826. 8vo.

(c) Introduction to a Treatise on Symptomatic Fevers, including Inflammations, &c. 4th Edit. London, 1820.