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till the ground-that the poison-seeds which fall upon it, instead of springing up in rank and deadly luxuriance, as in the case of the fatal epidemics of scarlet fever and other contagious diseases, should only find just enough of appropriate nourishment to enable them to germinate, and having exhausted the adaptation of the system to the whole species, should die down, leaving their sign-manual like vaccination, as a free pass against the assaults of any of their tribe-when we achieve this, we shall be approaching the consummation of the art, not only of curative, but of preventive medicine.
The principal charm by which Cullen captivated the medical mind of Europe, was not the wisdom displayed in his writings, but the completeness and ingenuity of his system of therapeutics as deduced from his physiology. Cullen starts with the following account of his notion of what life is "There is, seemingly, diffused over the whole of nature a quantity of electric matter, which, however, in the ordinary state of most bodies, shows no disposition to a peculiar mobility in passing from one to another; so that, though it is present, it does not show any disposition to motion, but we can by certain artifices accumulate this electric matter in more considerable quantity upon the surface of certain bodies, in consequence of which it can be put in motion from one body to another, exhibiting the various phenomena of electricity; and it is agreed upon among philosophers to call this Excitement, and to say that electricity is excited, and that such bodies are excited electrics, and all bodies may be so either by being excited themselves, or by having such bodies applied to them as are. So, in our medullary fibre, there is a fluid which was present in the germ, but was not excited; and it is in the excited state of this that I suppose life to consist; and when it is no longer excited in any degree, we call it the state of death; and I can suppose, as in electricity, it may exist
in different degrees." Again: "From what is now said of the excitement and collapse of the brain, it will appear that we suppose LIFE, so far as it is corporeal, to consist in the excitement of the nervous system, and especially of the brain, which unites the different parts, and forms them into a whole."
Life consists, according to this view, of a force generated in the nervous system diffused through the animal frame, just as electricity pervades inorganic bodies; the quantity of this vital force varies according to certain conditions, and the knowledge of these conditions will enable us to explain, as well as to obviate, morbid actions. Thus, this vital force will act as a powerful stimulus to any part where it is in excess, and may produce a state of contraction of the extreme vessels, while, on the other hand, an insufficient supply will induce relaxation.
But, in addition to this assumption of a vital force permeating the frame, Cullen assumed another force, which he called the Vis Medicatrix Natura; and in the interaction of these two forces he found an easy explanation of the most difficult problems in pathology. His most famous application of this theory was to fevers, and we may take his treatment of them as an example and illustration of his whole system of pathology and therapeutics.
According to him, fevers are, for the most part, the result of some depressing agent, either external, as malaria-or internal, as grief, anxiety, and such like emotions. The first effect of these causes is, to produce an imperfect generation of vital force by the brain; less life pervades the frame; in consequence, the extreme blood-vessels of the surface of the body fall into a state of atony, collapse, or relaxation. This condition alarms the vigilant guardian-the vis medicatrix. She comes to the rescue, and excites a counteraction in 1 Cullen's Physiology and Nosology, Vol. I., p. 131. 2 Ibid., p. 135.
these vessels to remedy the danger; but, like many allies, she rather overdoes her part, and instead of simply restoring the lost balance and generously withdrawing, she excites a contraction or spasm of these formerly-relaxed vessels, which constitutes the cold stage of fevers. Having done good to a certain point, and harm beyond it, it is clear that unless something came to counteract this dangerous sanative power, the unfortunate patient would die of nature's doctoring; so the vital force hurries into the field, and turns the table on the vis medicatrix, by producing a flow of blood into the contracted vessels, which distends them; and instead of the cold, shrivelled, shivering surface, there comes the full, warm glow, passing into intense burning heat-turgescence-and all the well-known symptoms of what is commonly called fever. The indication for the cure of fever is in strict accordance with this theory of its cause: we must relax the spasm of the extreme vessels— cut short the cold stage as rapidly as possible; for, upon the duration of this depends the amount of subsequent reaction.
Thus Cullen explained the action of Peruvian bark. The passage in which he gives his explanation has considerable historical interest, and may be worth quoting:"As the foundation of the whole of my doctrine, I consider the Peruvian bark, which, like other writers, I shall simply speak of under the title of the Bark, to be a substance in which the principles of bitter and astringent are conjoined. These are sufficiently obvious, and seem to be universally allowed. It may also have somewhat of an aromatic quality; but this certainly is not considerable, and I shall not take any further notice of it. As a bitter and astringent conjoined, I consider the Bark as a powerful tonic. As we have before shown, these qualities in their separate state give tonic medicines, so it will be readily allowed that, conjoined together, they may give one still more powerful; and as such, we
are now to consider the Bark in its effects and virtues, according as these appear in the various cases of disease."1
That we may understand the exact sense in which Cullen uses the word Tonic, let us hear his own definition :
"We have already taken pains to show that the tone of the moving fibres may depend partly on the mechanism of these fibres, but probably also upon the inherent power or state of the nervous fluid, as particularly modified in these fibres. If this last position be well founded, it will follow, that whilst on different occasions the tone of the moving fibres may be stronger or weaker, that may depend upon the state of the nervous power in the moving fibre being for the time different; and as this power may be acted upon and variously changed by substances applied to the body, we may allow that there are substances which, applied to the moving fibres, may induce that state of the nervous power, upon which their tone depends."2 The gist of this uncommonly cautious-worded paragraph, seems to be, that there are substances which act on the nervous system in such a way as to produce a greater quantity of nerve-force in the muscles, so that these contract with more readiness and strength. Cullen does not make the assertion that there is such a quality as nervous tonicity, and such medicines as tonics,-he only says that it is highly probable. Let us continue our former quotation.
"The first (of the medicinal powers of Bark) to be taken notice of is, its operation on the stomach. In many cases dyspeptic symptoms manifestly arise from a loss of tone in the muscular fibres of the stomach; and in such cases, as other bitters are, so the Bark is a remedy, and one of the most powerful. Nobody doubts of its being a tonic with regard to the stomach; and it is equally well known that the state of the stomach is readily communicated to the rest of the system. It is in no instance, however, more 2 Ibid, p. 54.
1 Cullen's Materia Medica.
remarkable than in the case of intermittent fever. That the Bark in this case operates by a tonic power, exerted in the stomach, I have endeavoured to explain in my " First Lines of the Practice of Physic;" and have met with nothing in any writers to make me doubt of the truth of my doctrine. It may, indeed, have its imperfections, and may not sufficiently explain the whole variety of phenomena which may occur in such a diversified and complicated system as that of the human body; but in attempting any general doctrine, we must begin with it as adapted to the most general and ordinary course of things. This, I hope, is done in my doctrine respecting fevers, and of the operation of the Bark in the cure of intermittents."
"We proceed, therefore, upon the supposition that the Bark possesses a tonic power, and that the action of this power on the stomach sufficiently explains its operations in preventing the recurrence of the paroxysms of intermittent fevers; for I see no foundation for referring it to any mysterious and unexplained specific power; which, however, some writers seem still disposed to maintain."1
The book from which this extract is taken, was published in 1789. The celebrity of its author secured it a welcome reception, not only in England but on the Continent. A few years after its appearance, it was translated into German by Dr. Samuel Hahnemann, who was at that time distinguished for his general accomplishments, and especially known as a chemist. The explanation of the action of the Bark in curing ague-a disease with which Hahnemann, residing in Leipzic, was very familiar-seems not to have satisfied the mind of Cullen's translator. He was probably struck with the frequency of the occurrence of the conditional mood in the two passages above quoted. Cullen begins by assuming that there may be what he calls muscular tone,—something different from Haller's irritability; again,
1 Materia Medica, Vol. II., p. 91.