In an inquiry of this kind, or indeed concerning any cause whatever, it is plain that the nature of the effect must be first understood. Fever then being an effect, we must begin with investigating its nature. But fever itself is only manifest by certain changes in the human body. Before we can investigate the nature of fever, therefore, we must investigate the human body, and that in a manner very different from what we did before. We must now consider the sources of life; in what manner the vital principle acts upon the body, and by what means its motions can be disturbed, or how they may be rectified when once disordered, &c. &c.
The systems of medicine before the time of Boerhaave are now so generally exploded, that it is needless to take any notice of them; and the reputation of Boerhaave himself in this way seems to be almost expiring. His doctrines, nevertheless, merit some attention, because he takes into account a principle overlooked by succeeding theorists, viz. the cohesion of the parts of the body. That he did so is evident, from his having written upon the diseases of a weak and lax fibre, and the diseases of a strong and rigid fibre. In other respects he followed in a great measure the mechanical physicians of the former century. He therefore took but little notice of the nervous system, as being less subject, or indeed to appearance not at all subject, to the known laws of mechanics. The blood was more manageable. The microscopical discoveries of Lewenhoeck furnished an excellent foundation for his system. This celebrated observer had discovered, or fancied he had discovered, that the red part of the blood is composed of globules. Inaccurate indeed these globules must have been, since each of them was composed of six; four touching one another in the middle, with one above, and one below, thus
. The serum was said to be composed of single globules, and by this attenuation it was supposed that the fluid, instead of red, appeared of a yellow colour. Still, however, this was insufficient. Each of the yellow globules was discovered (either by fancied observations or by conjecture, it matters not which) to be composed of six others, which, singly taken, might constitute the lymph or some other fluid; and thus, like the number of the Beast, we might go on by sixes to the end of the chapter, and solve all the phenomena of nature. In justice to the microscopists, however, it must be observed, that some of them have given a much less fanciful account of the structure of the blood than Lewenhoeck. Mr. Hewson found it composed of vesicles, or small bladder-like substances, with a black spot in the middle. These vesicles dissolved in pure water, but kept their original form, which he says was as flat as a shilling, when a small portion of neutral salt was added to the fluid. The solid particles he supposed to be produced by the lymphatic system; the black particles by the spleen.
The supposed observations of Lewenhoeck were of considerable use to Boerhaave in the forming of his system of medicine, though they seem not to have accorded very well with his doctrine of lentor or viscidity in the blood. But, let this be as it will, having laid it down as the foundation of his theory, that the diseases of the body proceeded from too great a laxity of the fibres, or from too great a rigidity of them, and a great many from this lentor, his practice was accordingly directed to such medicines as he imagined would remove these supposed causes of disease. As the lentor of the blood was one of his favourite suppositions, he was therefore perpetually at war with this imaginary enemy, and dealt very much in saponaceous medicines with a view to break it down. But here it is evident that this great man was mistaken, even though we should allow the existence of lentor as much as he pleased. The viscidity, lentor, or any other state of the blood, is an effect of something. It is part of that state into which the body is brought by the disease. The efforts of the physician therefore ought to be against that which produces the lentor; for, unless this be done, the cause of the disease must perpetually counteract the medicines by producing new lentor as fast as they destroy it; and besides, must have greatly the advantage of the physician, by being already in possession of the whole mass of blood, while the medicines can only enter it very gradually, and that by the stomach and lacteals, instead of being instantly mixed with it, and exerting their power immediately upon the fluid itself.
But besides this mistake, which is common to other systems, Boerhaave’s lentor has been denied, and that upon such strong grounds that it is now universally exploded. Another system quickly succeeded, in which every thing was managed by the nerves. This was introduced by Hoffman, adopted, and perhaps improved, by Dr. Cullen, under whose auspices it acquired such a degree of celebrity, that for a long time it was dangerous to write or speak against it; and the person who had the audacity to do so underwent a kind of medical proscription from the Edinburgh College and all its students. According to this celebrated theorist, the brain is that part of the body first formed in the embryo; it may be seen with nerves proceeding; from it long before the heart or any blood-vessel belonging to it is visible. Hence we are to conclude that this part is necessary to the existence of every other part of the body, though it doth not appear that they are essentially necessary to its existence. The superiority of the nerves to all other parts being thus established, the Doctor undertook to prove that all other parts of the body were formed from them; that the body is nourished immediately from them, and in short that the whole body is in such subjection to the nervous system, that, except for the mere purpose of distending the vessels, we can scarcely know for what end the blood exists; since the nerves can alter its consistence, or that of any of the fluids secreted from it, by a mere affection of that system, without any thing either added to or taken from the vital fluid.
Thus we were compelled to believe that all diseases at their first origin are affections of the nervous system, from whence they are propagated through the whole body. The Cullenian practice in acute diseases, of which the plague is the most violent, was built upon a maxim of Hoffman: “Atonia gigoit spasmos:” Atony produces spasms. In explaining the nature of typhus fever, therefore, with which he classes the plague, the Doctor supposed that the contagion acted first upon the nervous system, by producing therein a debility. The immediate effect of this debility is a spasm, or preternatural contraction of the capillary vessels, or extremely small arteries. Hence the blood finds some difficulty in circulating, and the patient is seized with shivering, and has a sense of cold. When this has continued for some time the system begins to re-act against its enemy; the spasm is resolved, and, the reaction of the system continuing, the action of the heart and arteries is augmented, and the body becomes warmer.
Thus the coldness, shivering, and consequent heat, which constitute the first attack of fever, are very plausibly explained; but in the mode of cure this learned physician fell into the same mistake with Dr. Boerhaave; for though spasm is undoubtedly, even according to himself, an effect, he directs his medicines entirely against it, as if it were a cause. Thus, forgetting what he had just before advanced, that the spasm is occasioned by debility, he recommended the most debilitating medicines and regimen to cure people already too much debilitated; and to such practice his enemies alledged that many fell victims. The theory and practice, however, still kept its ground; and as great numbers of students were every year bred up in the belief of it at Edinburgh College, who carried the principles of their teacher to all parts of the world, it bade fair for becoming universal. But, in the midst of this eclat, the whole system received such a rude shock from the doctrines of John Brown, though at that time not even M. D. as it hath not yet recovered.
Though the author of the new system contended, as much as Dr. Cullen, for the supremacy of the nerves, he did not upon that foundation attempt to establish his practice. He considered the living body as one machine, the whole of which might be acted upon, and always was acted upon by certain powers. It possesses a certain inexplicable property called excitability, capable of being augmented or diminished. Every power which augments the excitability he called a stimulus; the opposite would have been a sedative; but according to this system there is not any sedative, nor can there be one in nature. The reason is, that excitability itself has no existence but in consequence of the action of certain powers called stimulants. The total subduction of these reduces the excitability to nothing; of consequence no power can act against it in a state of non-existence. What other physicians call sedatives, therefore, according to the new system, are only weak stimulants. The fallacy of such reasoning is obvious; but as it does not affect the practice, we shall not spend any time in considering it further.
On the principles just now laid down, the Brunonian system divides all diseases to which the human body is liable into two great classes; the one produced by too much excitement, the other by too little. The former contains those diseases by other physicians called inflammatory; the latter such as are called nervous, putrid, or all in which the powers of life are too weak, and require to be supported. This last is supposed to be much more numerous than the former; and in the cure of these it was that the founder of the system appeared to greatest advantage. A most violent altercation took place between Dr. Brown and the Edinburgh College; yet, notwithstanding all the influence of the professors, and their unanimous opposition to the new doctrines, they found themselves ultimately unable to resist a single man unsupported either by wealth or reputation. The plausibility of his system, and its being obvious to every capacity, overcame every obstacle; so that even the practice of the Cullenians themselves underwent considerable alterations. It is not, however, to be denied that the system hath been considerably improved, or at least altered, by some of Dr. Brown’s pupils, who have had the advantage of extensive practice, and of visiting many different countries; which the Doctor himself never had. His materia medica was besides exceedingly confined; the only medicines he had any great opinion of, being laudanum and ardent spirits. The Peruvian bark he held in very little estimation, as being a weak stimulus. He seems to have been unacquainted with the virtues of mercury, except in the venereal disease, and most probably would have given laudanum in those cases of fever where mercury is found by others to be so efficacious. But this deficiency hath been abundantly supplied by some of his followers. In a work entitled “The Science of Life,” published by Dr. Yates and Mr. McLean, practitioners in the East Indies, we find mercury exhibited in prodigious doses. As a specimen we shall select their third case, which was a dysentery. On the first of September the patient took two grains of calomel and as much opium every two hours. This was continued for two days. On the third, the dose was given every hour; besides which, he had half an ounce of mercurial ointment with a drachm of calomel rubbed into his body. Next day the pills were continued, and the quantity of ointment tripled by thrice rubbing in. This was continued for three days, at which time, an eruption on the skin appearing, it was feared he could not be salivated; this eruption being a sign that no salivation could be produced. The same mode of treatment, however, was persisted in. September 7th the calomel in the pills was augmented to four grains; the warm bath was used, and the ointment continued; but at night twenty grains of calomel and six of opium were given every two hours. At the same time two ounces of ointment, with four of calomel, were ordered to be rubbed in. Next day, though his pulse was almost imperceptible, and his extremities cold, “the medicines were continued as far as circumstances would admit;” with what view it is not said, nor indeed is it easy to be discovered. At one in the morning, however, the patient died; an event not at all surprising. Our authors excuse themselves for this failure by saying that the viscera of the patient were diseased, as was evinced by the impossibility of exciting a salivation; and “that when a patient is evidently incurable by the common practice, it becomes the duty of the practitioner to depart from it.”