PATHOLOGY 397 the air-cell no longer containing air, but a solid coagulum consist ing of numerous threads of fibrin, with a homogeneous plasma as the basis, and a few red blood - disks and white blood - corpuscles (fig. 5o). The whole of this is an escape from the overloaded blood-capillaries. The lung is just one of those organs where such an escape from the blood is possible ; the engorged vessels are dis tributed as a plexus over the thin walls of air-filled spaces, and the fluid part of the blood, together with a certain proportion of its solid particles, passes through the walls of the vessels into the air space. If the lung be examined from a case of pneumonia fatal a day or two later, or in the third stage, it is still solid, but the redness is mottled with grey, or has become uniformly grey. The number of round nuclear cells in the air -vesicles has increased enormously, usurp ing the place of the fibrin and plasma (fig. 56). There is no good reason to suppose that this enormous accumulation of cells is due to successive additions of colourless cor puscles from the blood ; they are now, many of them, much larger than the blood -cells, and we may take it that they are the product either of sub division of the few original blood -cells or of the epithe lium of the air-vesicles. The solidity now begins to give way, the contents of the air- Fl ?- M ;-^ eum( ; nic I""? , ste ?e of grey
- . i , . hepatization ; alveoli filled with cells.
vesicles undergoing a mucoid or other disintegration, and they are gradually removed for the most part by expectoration. In ten days from the onset the lung may have returned to its normal condition. We have now to consider briefly this disease as an error in the heat-regulating mechanism, in which the strain falls upon an im portant peripheral or executive part. Hepatitis may be taken to be this kind of effect where the chill is a slight abstraction of the body s heat under tropical conditions ; pneumonia is this kind of effect where the chill is caught under the vicissitudes of the weather in spring, or in changeable weather generally, within the temperate zone. Why should the liver be the organ of choice in the one case and the lung in the other? It may be said at least that each organ, in the respective circumstances, is the locus mino- ris rcsistentiae. A sudden abstraction of heat is a strain or shock to the heat-regulating centre, and, if the incidence is to be on the executive, it will fall on that member of the executive whose function had been, under the circumstances, most taxed. It is to be remarked that such cases of so-called peripheral incidence are associated with individual predisposition ; hence these diseases are generally sporadic. Something in the antecedents of the individual has determined the local character of the effects of chill, whereas the great climatic fevers more uniformly befall those who expose themselves. Rheumatic Fever. Eheumatic fever is universally admitted to be an effect of chill. " I know of no other exciting cause of acute rheumatism," says Watson, "than exposure to cold, and especially cold combined with moisture. " The conditions, both external and predisposing in the individual, which constitute the peculiar lia bility to rheumatic fever are nowhere found more distinctively than in the variable climate of the British Islands, and in the habit of body of the people. It is especially a disease of early manhood and womanhood, and of the working class ; when it occurs before puberty it is associated in a remarkable way with the liability to chorea. The onset of the fever is preceded for a few days by general ill health, chilliness, furred tongue, " break- bone " pains, flying pains in the joints, some quinsy, and disturbed sleep. If these symptoms proceed no farther, the patient would be judged to have had a chill, a catarrhal attack, a quinsy, or the like. When the initial upset has been more considerable the pains "settle" in one or more of the larger joints, often the ankles at first, the knees subsequently, or the wrists, elbows, and shoulders. The patient lies flat on his back, not daring to move, and following the objects around with his eyes only. Profuse sweats break out from time to time, having a peculiar acrid smell, by which rheumatic fever can even be diagnosed. The joints where the acute pain is seated for the time being are swollen, tender, and often red and hot, the swelling being either in the fibrous structures around the joint or in its synovial cavity. The locale both of pain and swelling shifts from joint to joint ; the disease often "flies to the heart" (pericardium and endocardium), more rarely it "flies to the brain " (membranes). The urine is scanty, high-coloured, depositing brick -red urates, and with an excess of urea on analysis ; it is, in fact, the urine of disordered heat -regulation. The temperature is 100 or 101 up to 104 or 105, and in some exceptional cases (of "hyperpyrexia") rising to 109 Fahr. There is an afternoon rise of 1 or more, and a corresponding fall in the night. The severity of the case apart from its danger, which really depends on the pericardial or endocardial part of the disease, or on complications with pneu monia and the like is measured by the height of the tempera ture, with which, again, the intensity of the pain in the joints goes hand in hand. The outbreaks of sweat do not follow any obvious law, and they are not "critical," as in intcrmittents ; but they seem to give the patient relief for the time, even if they leave weakness behind. Nine days is considered an average time for such an attack to run its course if the patient be well cared for ; but defervescence is gradual, and complete restoration to health is often slow, much weakness and anaemia remaining to be made good. Warren, a physician of a former generation, when asked what was the best remedy for rheumatic fever, answered "Six weeks." Relapse is not uncommon, a very slight chill or sudden abstraction of heat sufficing to bring the fever back. Now if we assume that the occasion of an attack of rheumatic fever is chill that is to say, a sudden shock or injury to, or dis organization of, the nervous centre which presides over the uniform body -temperature we enter upon a profoundly interesting prob lem in following out the constitutional manifestations. Every thing points to the mechanisms of locomotion, to the structures and surfaces where muscular work is applied ; even the heart, as Watson remarks, is in its perpetual to-and-fro movement comparable to " one of the large joints." There is heat of combustion from some source or another to account for the rise of temperature, which is sometimes enormous ; but it is not the heat of work done. We are again confronted with that most fundamental of all the questions relating to fever, the question, as stated by Foster, whether the " metabolism of even muscular tissue might be influenced by nerv ous or by other agency in such a way that a large decomposition of the muscular substance, productive of much heat, might take place without any contraction being necessarily caused ... in such a way that all the energy set free would take on the form of heat." Is rheumatic fever one of those cases where disorder of the heat- regulating mechanism falls on an important member of the exe cutive, namely, the muscular system, just as it falls on the liver in tropical abscess, and on the lungs in pneumonia ? Certainly we know of no muscle but the heart itself which The shows appreciable structural changes in rheumatic fever ; the heart articular is liable to " myocarditis," as well as to endocarditis and pericarditis, nerves, but, for all other muscles, the changes are in the tendons, liga ments, and synovial membranes only, or, in fact, in those structures by which the work of muscles is applied. These structures have nerves, some of them large enough to be looked for in the dis secting-room, although less is made of them in physiology. The function of the nerves of the joints is not sensory in the ordinary use of the term, but it may be said to be to convey to the centres the sense of effect of the work done by muscles. When there is intense metabolism of the muscular substance, but no work done, the same nerves, having no sense of effect to convey, convey an acute sense of pain. The pain of rheumatic fever is altogether more acute than in inflammations. In tropical abscess pain is subordinate, and its place is taken by a vague feeling of trouble, or tightness, or weight, or heat in the hypochondrium, and tho same substitution is sometimes made for the pain in pneumonia ; but in rheumatic fever pain may be said always to be the grand symptom, and a measure of the very remarkable power of recovery. Reversing the maxim which applies to tropical abscess and to the worst cases of pneumonia, we may say of rheumatic fever : " Affert plus doloris quam periculi. " Sweating is the other grand symptom of rheumatic fever. It can hardly be said to be critical for the disease as a whole, because the temperature does not fall ; but the joints affected for the time being are relieved by it, and it is critical to that extent. We may, indeed, say that the temperature does not fall because the heat goes on being generated in some other group or groups of muscles in whose joint or joints the pain is next felt. We may regard, then, the sequence of events in rheumatic fever somewhat as follows. There is an upset of the heat-regulating centre by chill, owing to which an extravagant amount of heat- generating nerve-influence is sent out ; this falls, for some reason of the body s habit (inherited or proper to the individual s occupa tion, or otherwise special), upon the muscular system, whose meta bolism produces heat without work ; the articular nerves which are ordinarily employed to convey the sense of effect of woik done, from the surfaces where the movement is applied, convey, under the changed circumstances of the muscles activity, a sense of pain. One set of muscles after another generates heat without work, so that one joint becomes painful after another ; and, although there are perspirations by which the heat of the body is parted with, other sets of muscles take up the work of combustion in their turn, so that the excessive temperature is maintained. Among other muscles the heart is affected; and, just as in the voluntary- muscles the structural effects are in the synovial membranes, ligaments,
