Page:Encyclopædia Britannica, Ninth Edition, v. 18.djvu/417

395 vulsion is. It can hardly be doubted that in the repetition of a simple ague -paroxysm we are concerned, not with the nervous system as co-ordinating the two sides of the account in the produc tion and discharge of animal heat, but with an acquired habit of the nervous system, with a usurpation of the power committed to it for the purposes of control only. This acquired faculty of the heat-regulating centre to act quasi-autocratically is often exempli fied in those persons who, having suffered from malarial fever under its usual exciting circumstances, experience a return of it under widely different circumstances. Thus, a pronounced ague-shake has occurred to a person crossing an ice-slope 10,000 feet above the sea-level, the original ague having been contracted several years before in a malarious locality. We come next to the circumstances under which the heat-regu lating centre sutfers this disorganization, the memory of which may remain with it for long after. The circumstances of intermittent and remittent fevers have been already discussed in the article MALARIA, and it remains to give here only a brief epitome. Where- ever and Avhenever malarial fevers occur there are considerable degrees of solar heat and of moisture in the lowest stratum of the air, and a considerable drop of the temperature after sunset. So far as the individual is concerned, he incurs risk by working in the sun and resting or sleeping in the chill of the evening, by letting a wind such as the monsoon blow upon his fatigued body, by passing suddenly from the relaxing conditions of heat to the constricting conditions of cold, by arriving from cooler latitudes in the hot season, and by doing one or all of these things when his nervous power, as Cullen said, is enfeebled by such causes as anxiety, in temperance in drinking, "and other circumstances which evidently weaken the system." A high degree of moisture in the lowest stratum of the air is the most universal of the external factors within the malarious latitudes, and it may be produced either by the extreme dampness of the soil or by the extremely rapid cooling of a dry soil (even bare rocks) by radiation of heat after sunset, whereby a moderate degree of atmospheric moisture gives a fall of dew. On the other hand, wherever the atmosphere is exceptionally dry, as on the southern littoral of Australia, there is no malaria notwithstanding the great solar heat ; and wherever there are only a few degrees of difference between the day and night temperature and a very slight range throughout the year, as at sea within the tropics, or at such localities as Singapore and the Amazon valley under the line, malaria is far less active than the great solar heat and moisture might lead one to expect. Whatever in the telluric and atmospheric surroundings taxes the nervous mechanism which keeps the heat of the body always about 98 or 99 Fahr. is a cause of malarial fever. ( d fit The Cold Fit of Fever. The central point of interest in a par- c fever, oxysm of fever, the grand paradox of fever-pathology, is the rise of the heat of combustion, as shown by the clinical thermometer, and the simultaneous closing of the natural outlets of excessive heat, as shown by the shivering and the feeling of "goose-skin." The value of any pathological doctrine of intermittent and remit tent fever may be estimated by its success in dealing with this paradox. We may conveniently approach this subject through the following concrete instance, as given by Oldham. "At Jhansi, in June 1860, a young officer of the battery of artillery to which I belonged was exposed for some time to the sun at mid-day ; he then, in a profuse perspiration, came into the house, through which a hot wind was blowing, as all the woodwork had been burned by the rebels, and the tatties, which served for doors and windows, were almost dry ; in a few minutes he complained of being chilly, and in a few more he was in the cold stage of a sharp attack of intermittent. This officer had never previously suffered from fever ; when he went out a short time before he was in perfect health, and he had not, whilst away, been into any malarious locality ; in fact, at that season, the whole country round was parched and dry." This case illustrates an important point, antecedent exposure to great solar heat. Exer cise in the sun means active internal combustion in the muscles, liver, &c. , and the body warmed at the same time by the sun s rays ; the equalizing of the heat made and the heat lost is accord ingly a difficult task, which falls mostly on the skin (and lungs) to execute, and the heat - regulating centre to order and control. We may take it that both the regulating function of the nerve- centre and the executive function of the skin are strained to the utmost. In the case quoted, where there was no interval between the cause and the effect, the body in its glowing state is suddenly exposed to a slight abstraction of heat through the draught in the house ; the sudden loss of heat, however slight the amount, is the signal for the skin to close its pores so as to lose no more heat, and hence the passing feeling of chill. But the passing feeling of chill is in this case succeeded, at only a few minutes interval, by the prolonged state of con traction of the cutaneous vessels, sweat-glands, and other muscular structures which corresponds to the rigors and the cold fit of ague ; and, all the while that the skin is thus vigor ously adapting itself to prevent the escape of heat, the heat of the body is rising several degrees. The skin and the nervous centre, the executive and the central authority, are at cross purposes so far as the object is to keep the temperature at the level of 98 or 99 J Fahr. Now, the rise of temperature in this case can have had no other source than internal combustion (in the liver, muscles, brain, &c. ) ; but the combustion is an unnatural one, inasmuch as no proper physiological work has been got as its equivalent out of the muscles, brain, or liver, although there has been the due physio logical waste (carbonic acid and urea). A slight chill, or the sudden abstraction of a not very large amount of heat from the surface of the body, has excited the heat-regulating centre in such a way that it lets loose an extravagant amount of its " thermogenic " force. 1 The nervous centre has been called upon to equalize the slight abstraction of heat at a moment when it is still in the state of strain from its previous and well - sustained efforts to keep the balance, and it is upset by the sudden call. It answers by an altogether disproportionate discharge of its force, which is both ill adapted to the momentary needs of the body and continues in operation much beyond the occasion for it. Under ordinary circumstances of taking the ague there is usually an interval between the exposure to heat and the exposure to chill. Usually, also, the exposure to heat is more or less prolonged or habitual ; the heat-regulating centre is taxed over and over again, and it is taxed so much the more if there is moisture in the air along with solar heat, the dissipation of the body s heat by the insensible perspiration and by radiation being much more difficult in a damp atmosphere than in a dry. Whenever the chill comes, it finds the heat-regulating centre without that tone which would enable it to act according to the emergency, so that the abstraction of heat, even if it be slight, is the signal for an enormous stirring up of all the internal iires and a rapid combustion to meet a loss of heat which is not greater than the body endures under other circum stances with impunity. This phenomenal burst of heat-making is, so to speak, misunderstood by the motor nerves of the skin ; when ever, under the same circumstances of repose, there is the same thermogenic activity, it means that the heat is wanted to keep up the level of 98 or 99 Fahr., and all the muscular elements in the skin and in its vessels contract to keep the heat in, producing the feeling of external cold, or of shivering if the contraction be extreme. The same thing happens under the incoherent and extravagant action of the heat-regulating centre ; and hence the paradox of the body shivering all the while that its internal heat is rising to 5 or 6 Fahr. above the average of health. Another way of expressing the paradox is to employ Bernard s A long language of " thermic nerves " ; we should then say that stimula- cold lit tion of "calorific nerves " goes with a stimulation of " vaso-con- means a stricter" nerves in the skin, so that a violent discharge of force mild along the one path is associated with a violent discharge along the fever, other. Whether, as Traube has suggested, the extravagant action of the heat-regulating centre might be altogether counteracted by the usual heat -discharging mechanism but for the inopportune constriction in the cutaneous vessels and the surface of the body generally, is a curious question, but hardly a practical one. In that degree of shock to or disorganization of the nerve-centre which occurs in ordinary tertian or quartan intermittent the dura tion and degree of the shivering fit are the index of the mildness of the attack ; the more pronounced the cold stage, the more prompt is the crisis and the more certain the defervescence. But in the much more severe shock which brings a quotidian or a remittent, the cold stage is short and feeble, and the crisis and defervescence are proportionately undecided and uncertain. The remittent degree of climatic fever approximates, indeed, to the forms of continued fever in which the rigor is a mere survival of the great cold fit of intermittent ; the initial rigors even of pneumonia are little more than formal, and the hot stage of the process is practically the whole. It would thus appear that the vaso-motor constriction, upon which the phenomena of the cold fit depend, is the due accompaniment of a certain moderate degree of upset in the thermogenic nerve- mechanism ; the paradox of the body shivering while its internal heat is rising is after all a paradox, and not an antagonism. The severer types of climatic fever are those in which the primary shock has been most severe or least well sustained. " Degrees of fever," says Ferguson, "might be almost measured by degrees of solar heat, from the agues of Lincolnshire to the malignant remittents of the West Indies." The periodicity of agues is a reflex of the normal periodicities Period- of the bodily heat ; in health the temperature rises to its highest icity of point in the course of the afternoon and falls to its lowest a little agues, after midnight, and in a typical intermittent these are usually the 1 " There is no a priori reason," says Foster (Text-book of Physiology, p. 377), "positively contradicting the hypothesis that the metabolism of even muscular tissue might be influenced by nervous 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. If we were to permit ourselves to suppose that the contractile material whose meta bolism when resulting in a contraction gives rise to so much heat, could undergo the same amount of metabolism, in so far a different fashion that all the energy thereby set free took on the form of heat, variations in the temperature of the body, at present difficult to understand, would become readily intelligible."