518 CHAP. XXX. ON DISTURBED BALANCE OF CIRCULATION, AND METASTASIS OF DISEASE. I PLACE these subjects together, not merely for mutual illustration, but because in some points they can scarcely be regarded apart, when looking to the phenomena of disease. It is another instance where much may be added to the extent and clearness of our views in pathology, by considering different disorders in relation to some common principle of morbid action. We thereby, even without aiming at new classification, gain knowledge of connexions, which escape notice, if confining ourselves to a single view, or to the limits of systematic nomenclature; and we obtain moreover various aids in practice, made more secure by resting on a wider basis. Disorder or irregularity in the circulation of the blood, by whatsoever names in its different forms described, is such a principle of morbid action; -more universal perhaps, and more important in its effects, than any other in the animal economy. Taking the expression, indeed, in its largest sense, it may be said to involve every possible form of disease. Scarcely one can be named, in which some unequal balance of blood, local or general, does not exist. From acute local inflammation of the most urgent kind, to chronic inflammation, plethora, or congestion, under the lightest forms; and again, to those momentary and ever-changing misdirections of blood which occur in some nervous disorders; we have a long series of morbid changes, in all of which this common fact is concerned, however various the causes of inequality, and however different, or even opposite, the state of the vascular system in the changes taking place. It is further to be remarked, that all these morbid actions have connexion, more or less intimate, with corresponding changes in the healthy state; and that they become anormal chiefly by excess in amount or duration. The inequalities in circulation produced by mental emotion; by bodily exertion or posture; by digestion in its several stages; by exposure to heat or cold, or other atmospheric changes; represent in degree, or for a time, almost all such as are considered morbid in kind, and often pass into the latter without any obvious interval between. This manner of viewing the subject, through the relation of disordered actions to those of health, is here, as in all other cases, the best; whether we look to the theory of disease, or to its treatment in daily practice. It is difficult, from the nature of the subject, to classify the various disturbances in the balance of circulation. The most general distinction might be that between inflammation, in the common sense of the term; and those irregularities, often much more extensive and sudden, but where none of the characteristic marks of inflammation are present. Here, however, besides many exceptions and doubtful cases, we come upon the wider question, whether there are any distinctive characters of inflammation, certain enough to warrant their being thus classed apart. This doubt reasonably arises as a result of all modern inquiry on the subject. Though it may be difficult to go with one eminent pathologist so far as to remove the term inflammation from medical use, yet it is certain that the gradation in all these states is such, as not to allow any fixed lines of demarcation to be drawn, without error in fact, and frequent injury in practice.* Still the pathological differences for each end of the scale are so strongly marked, as fully to justify their separate consideration; and though the notion of metastasis, as commonly received, applies to both classes of phenomena, there is convenience here also in keeping some such distinction in view. So much has been written upon inflammation that it is not easy to add either fact or opinion to those already before us. But the other inequalities of circulation, though more considered of late years, have not received the same minute attention. From the difference of the phenomena, research is here more difficult; and on many points we are limited at present to facts drawn from other parts of the animal economy. This very connexion, however, is matter of great interest to pathology; and in all points of view these unequal distributions of blood, which, without local inflammation, con All who have read on this subject, as well as studied it in actual practice, will be conscious of its many perplexities; and of the frequent impossibility of diagnosis between inflammation and simple congestion, or the more singular phenomena of turgescence. As an example of these difficulties, we might specify some of those curious instances, in which a state, having many of the received characters of inflammation, is actually brought on by causes of depletion, such as increase the proportion of serum to the coagulum of the blood; and is relieved by opposite treatOther anomalies might be named, familiar to every practitioner. Some of these may best be explained by looking less than is usually done to the mere vascular tissue of an inflamed part, and more to the state of the fluid within the vessels, as primarily affected by the causes of inflammation, and determining the changes which ensue, both in the part itself, and the system at large. An experimental memoir by Dr. Alison, read at the meeting of the British Association at Dublin (see Report of Sections, p. 88.), has great value in relation to this topic. ment. The opinion, advocated by Dr. Macartney, that inflammation can never be rightly considered a reparative process, is another proof of the uncertainty which still hangs over every part of this subject. stitute so many forms of active disorder, deserve the diligent attention of the physician. The most general manner of viewing the subject regards the causes and conditions under which the blood is thus unequally transferred from one place to another, producing local excess or deficiency, as the case may be. It is clear that there is a natural balance, or proportion, of blood to the several parts of the body respectively; certain, and often great, deviations from which are compatible with health, or even essential to the functions of life; while yet greater deviations, or such as affect particular organs, or occur too suddenly, fall strictly within the name and character of disease. What are the physical causes producing these changes? Why is it, that even in healthy actions, and more remarkably in those of disease, mutual exchange of blood should take place, by sudden determination, between the skin and internal membranes? or why those more vague and various translations of blood which occur among different organs, without apparent unity of cause; as the brain; the membranes lining the air-passages; the pleura and lungs; the peritoneum and membranes of the alimentary canal; the liver; the kidneys; the organs of generation; the mamma; the synovial membranes? &c. That there are parts of the body more closely connected than others as respects these translations, and that there is some relation here both to similarity of texture and community of function, is certain from observation. But even could we derive any direct explanation from this, the facts would call upon us to go beyond it; and to show cause for those sudden changes in the balance and direction of the blood, where the structure and function of the parts successively affected are wholly different in kind. Or it may be needful to enlarge the inquiry, to include the cases where, without actual increase or diminution in the quantity of blood in an organ, the rate of its motion is topically altered, so as to change for a time the condition of the part. It is not easy, indeed, to prove that such case exists. If it does (and perhaps the circulation through the brain furnishes the most probable instance), it comes within the scope of the subject, and receives illustration from the remarks which follow. Four conditions at least may be taken into question, as respects the rationale of these changes. First, the variations in the heart's action:- Secondly, the state of the capillaries of the parts to which the blood is for the time directed: - Thirdly, the quality or quantity of the blood itself:- Fourthly, the influence of the nervous power upon the circulation. These conditions are in many ways closely blended together; yet each is distinct enough to deserve separate consideration. The first is by no means the most important, though on superficial view it might seem to be so. By whatever influence the action of the heart is produced (and the question, as regards the nervous system, has scarcely yet been decided), its immediate effect in propelling the blood towards the extreme vessels is one mechanical in kind; nor have we any certain proof that the arteries aid in this transmission by any power which they themselves possess. The action of the heart may be excessive or deficient in force: it may be disordered in frequency, regularity, or other characters of pulse: but still these inequalities affect more or less all parts of the vascular system; depending chiefly on the greater or less power of propelling blood into the minute vessels. The general inference remains the same, whatever opinion we adopt upon the questions still perplexing physiologists in respect to the circulation whether there be other motive power than that of the heart? - whether the arteries or capillaries have - |
