to remove something that is noxious, and which, by its continuance, would disturb the system or destroy it.

"This theory of fever amounts to no more than saying that there are certain states of the body which are combined together in a certain order of succession, and that, from this constant combination, they are to be considered as a series of causes and effects. This I assume as a fact, and I suppose that this connection is determined by a certain mechanism or organization of the body; but I do not pretend to explain the nature of this. I might offer conjectures upon this subject; but while they are only conjectures, I shall not trouble you with them, so shall go no farther. But the length we have gone, I hope we shall find it applicable to the practice, for I have only referred some part of the connection to a certain general law of the system, to the vis medicatrix naturæ or autocrateia, which, though it does not explain the connection, assists in establishing it."

That to trace the order in which the phenomena of the animal economy succeed to one another, and, from this succession of external phenomena, to attempt to infer, what is the succession of internal pathological conditions, or, in the language of some pathologists, to arrive at the ratio symptomatum-in each form of disease, was the object which Dr Cullen kept constantly in view in all his observations and speculations, and of which he proposed to exhibit an example in the composition of his First Lines of the Practice of Physic, may be presumed, not only from the rules which he laid down for himself, but also from the manner in which every part of that work has been executed. His main design in this respect, however, seems to have been but little if at all perceived or understood by many of his critics, who

have so often regarded and represented the generalizations to which he was led from observation, reading, and reflection, as merely hypothetical assumptions. Every re-perusal of Dr Cullen's First Lines of the Practice of Physic, and comparison of them with the other medical text-books at that time in existence, or which have since appeared, tends to confirm me in the belief that his work exhibits in the execution of all its parts, but particularly of that relating to fever, the most skilful and successful application of the principles of inductive philosophy, to the study and practice of physic, that has ever been made by any single physician; and notwithstanding all the advances which have since been made in the auxiliary and collateral branches of medical science, and particularly of pathological anatomy, I doubt whether it has yet been, or is likely soon to be, surpassed or equalled.

"It is not Dr Cullen's praise," as has been well observed by Dr Wilson Philip," that he invented an ingenious hypothesis, but that he new-modelled, if I may use the expression, the whole practice of medicine; that, in his Synopsis Nosologiæ Methodicæ, he defined and arranged diseases with an accuracy that is still unrivalled; and, in his First Lines, reduced their treatment to a degree of simplicity formerly unknown.”

The view which Dr Cullen took of the Remote Causes of Fever, must be acknowledged, even by those who may be disposed to question its accuracy, to have presented this subject under a much more simple aspect, and one more calculated for the elucidation of truth, than any in which it had ever previously been exhibited; and if its details cannot be conidered as having originated with him, he is certainly

entitled to the credit of having put them together in such a way as to constitute a general doctrine, capable of improvement according to the progress of knowledge.

Dr Cullen conceived that the remote causes of fever are chiefly of two kinds, viz. 1st, Effluvia from the Human body; and, 2d, Effluvia from other substances, and particularly from Marshes. The effluvia of the former description he regarded as the principal cause of Continued, and those of the latter as the principal, if not the only, cause of Intermittent fevers; and he conceived that, for general purposes, these two kinds of effluvia may be distinguished from one another by the names of Contagions and Miasmata. He was perfectly aware of the fact which has been adverted to by Dr Good, that the terms Miasma and Contagion do not, etymologically considered, justify the signification which he has attached to them; but the accurate definitions he has given of the sense in which he proposes to employ these terms, in the 78th and 84th paragraphs of his First Lines, and which a very slight modification would render perhaps unobjectionable, make this a matter of little importance. Dr Good says, that "no great benefit has resulted from endeavouring to draw a line of distinction between these two terms, and that hence it is a distinction which has been very little attended to of late years." It may be questioned, however, whether the reverse of Dr Good's proposition would not more correctly express the fact, that the little attention which has been paid to this distinction, has prevented the benefit which would otherwise have arisen from its observance.

The very curious and important investigation into the source and natural history of the Agent which produces Intermittent and Remittent Fevers,-commenced by Lancisi in Italy, and followed up by the excellent and accurate observations of Sir John Pringle, and Dr Lind, the three authorities upon which, conjointly with his own experience, Dr Cullen chiefly relied in his speculations upon this subject,*-has been continued to the present day by a succession of zealous and intelligent medical philosophers and practitioners in all the different regions of the globe. Many efforts have been made to demonstrate the physical existence, and to ascertain the chemical nature of this agent, the precise conditions of its origin, the laws of its dispersion through the atmosphere, and particularly the distance to which it may be conveyed, by atmospheric currents, from the seat of its production. But though intermittent and remittent fevers have been observed to occur chiefly in the neighbourhood of marshes, and the name of marsh poison has, from this circumstance, been generally applied to the agent to which their production is attributable, it is conceivable that the combination of conditions essential to its development, including peculiarities of soil, moisture, and heat, may occur in situations that cannot be strictly designated as marshes; and that intermittent and remittent fevers may consequently arise

* Torti, Werlhoff, and Cleghorn, were Dr Cullen's chief authorities on the varieties of Intermittent Fevers.

See particularly the writings of Sir Gilbert Blane, Monfalcon, and Dr Maculloch.

in such situations; and it is conceivable, also, that in situations which usually fall under the designation of marshes, the necessary combination of conditions may be wanting, so that the morbific agent shall not arise, and consequently intermittent and remittent fevers shall not be developed. On the whole, it seems probable that this morbific agent is always present and active in warm climates; but that in the temperate and colder, its generation being dependent on the simultaneous and alternate action of heat and moisture, it is chiefly at the stated periods of spring and autumn that its operation is rendered most manifest. For an excellent summary of the results of the observations and experiments that have been made on this important subject, I have much pleasure in referring to the chapter on Ague in the Elements of the Practice of Physic by my learned and intelligent friend Dr Craigie.

It is well known that in warm climates, not only are intermittent and remittent fevers convertible into one another, but they not unfrequently pass into fevers of a continued type; whilst those of a continued type pass, though perhaps less frequently, into intermittent and remittent fevers. It is equally well known that, in the British islands, and in every other country of Europe, there exist fevers of a continued type, which occur sporadically, and even sometimes prevail epidemically, without there being any reason to believe that they have had their origin in human effluvia, or that

* See the interesting observations of Dr W. Ferguson and Dr Wilson.