the elements, as it were, of others; and, 3d, how many diseases are compounded of these, has sketched what may perhaps be regarded as the outlines of an arrangement of diseases, under these two heads, of Simple or Primary and Compound. He establishes his differences of diseases on the division of the parts of the body into similar and organic, or, in the language of the moderns, those of textures and organs, and endeavours to accommodate it to either the methodic doctrine of dilatation and constriction of the passages, or to the Democritic doctrine of the four elements. Galen has not, however, attempted an enumeration of the diseases referable to each of the divisions of which he has thus sketched the plan.

The Arabian physicians and their successors, as Sennertus has remarked, passing over the general methods of arrangement pursued by the Greeks, considered diseases, with their causes, signs, and cures, in the order of the parts of the body in which they occur, as those of the head, of the chest, of the abdomen, &c.; and this arrangement Sennertus, in designating it the customary order of practical physicians, himself adopted in his Medicina Practica, published in successive parts between 1628 and 1635.

To Felix Plater is attributed the merit of having first proposed, in his Medicina Practica, published in 1602, an arrangement of diseases into classes, founded on the more remarkable analogies of their phenomena or symptoms, or, in his own words, "according to those manifest affections which fall under the senses, or which are perceived by the senses of the sick, or of the bystanders, and concerning which patients first complain

to their physicians." The highest genera or first heads established by Plater, in conformity with this view, were, 1st, The lesions of the functions, comprehending those of Sense and Motion; 2d, Pains or Uneasy Sensations; and 3d, Those morbid affections which have been termed Vitia, and which may be considered as corresponding with structural alterations.

But, as has already been observed in speaking of the definitions of diseases, it is to Sauvages that medicine is indebted for the first system of Nosological Classification, executed in conformity with those logical principles which had been applied to the classification of the several subjects of natural history; a classification having for its purpose, by a succession of divisions and subdivisions, to each of which is attached a definition expressive of certain determinate and obvious characters common to all the lower genera comprehended under it, to enable the practitioner gradually to circumscribe the number of objects of comparison, and thus arrive at length at the precise species to which the particular individual case under his observation is referable.

The principal advantage calculated to result from the institution of nosological classes and orders, appeared to Dr Cullen to be the necessity which every such attempt imposes on those who engage in it, of marking very accurately the characteristic phenomena of particular diseases.

"In natural history," says he, "it is the attempts towards a system that have produced the knowledge of particulars; and though these are, in their turn, necessary to render the system perfect, it has, however, been especially every new ef

fort in system that has excited a new industry in completing and rendering more accurate the knowledge of particulars. The system of Tournefort, for example, led to a more exact observation of the form of flowers; that of Rivinus directed attention to the number and disposition of the leaves; a slight attempt by Vaillant and Boerhaave led to the studying of stamens and pistils: and the system of Linnæus has carried the same much farther. In short, I think every body acquainted with the progress of natural history must know that the attempts in system and the study of particulars have mutually promoted and supported each other."-" It is certainly the same with regard to diseases. If a system-a nosologia methodica-cannot just now be rendered tolerably perfect, it is a certain proof that the particulars of which it should be formed are at present neither accurate nor complete; and it is equally probable that they cannot be rendered so till our attempts in system have been repeated, and have made some farther progress. Our attempts in system are necessary to enlarge our stock of facts. The formation even of classes and orders may, in many cases, contribute to a fuller and more exact distinction of the species. For though we cannot at all times obtain a certain and accurate arrangement of this kind, yet the very attempts to obtain it must be of great use, by leading every now and then to useful discussions both in pathology and in the history of diseases. Diseases must be distinguished both by the symptoms peculiar to each, and by those common to each with some others; which is nothing else than to distinguish diseases as all other things in nature should be distinguished,—by species and genera, and a distinction of this kind necessarily requires the noting both of the lower and of the higher genera."

Dr Cullen never set a high value either on his own labours or on those of other nosologists, so far as these

had merely for their object the arrangement or classification of diseases.

"Those who have applied to this study before us," he remarks, "have, as it appears to me, gone improperly about the matter; for, paying little attention to the species, they have been occupied in constituting classes, orders, and genera. But by nature, species only are given the formation of genera is the production of the human mind, and must be fallacious and uncertain till all the species are well known and distinguished; and our labour in constituting genera, unless we always have regard to the species, will be vain and futile.”—“I am so far from thinking that we ought to enter anxiously into the general systematic arrangement, that, in my Prolegomena, I have insinuated a contrary notion. Because I think there is use in the attempt, I have, with others, endeavoured to form classes and orders; but for the accuracy of these, I would by no means vouch. I have many difficulties still with regard to them, and I think I could still point out considerable improvements; but my labour is to study genera in the first place, and, when I can arrive at them more certainly, species. If I can distinguish these with tolerable accuracy, I am not concerned with my distribution into classes and orders being more or less exact. is from our accuracy with respect to the species that all the rest of the divisions can be properly established; and in nosology, indeed, we are very much relieved, by the smallness of the number of the objects to be arranged, from a more particular attention to classes and orders."

It

"When the things to be distinguished are very numerous, it seems to be very useful and necessary, both for the investigation and remembrance of them, that they should be referred to some higher genera; but when the species of these things are not very numerous, and it does not exceed the powers of most men's memories to remember them, there

scarcely seems any necessity of referring them, with great solicitude, to classes and orders."

With Dr Cullen's recorded statement of the slight degree of importance which he himself attached to the portion of his nosological labours relating to systematic arrangement, it seems superfluous to enter on any lengthened consideration of the various criticisms to which this part of his work has been subjected; the more so that a large share of these criticisms were anticipated and discussed by himself, either in the Prolegomena or in the Notes to his Nosological System, though his remarks respecting them have seldom, if ever, been recognised or adverted to by his critics, who have brought forth their objections as if they were entirely original, and as if they afforded so many proofs of their own superior discrimination and knowledge of the subject. A few remarks, however, on some of the more prominent of these criticisms will best serve to shew how far they should be considered as detracting from the general merit of Dr Cullen's Nosological System.

Dr Cullen, as is well known, arranged diseases in that system, under four primary divisions or classes, viz. Pyrexiæ, Neuroses, Cachexia, and Locales. Dr Mason Good has objected to this division, on the ground that "the class Locales has no scientific relation to the other three classes, no parallel or apposition with them. To have brought it into any such kind of bearing, the whole of the three first classes should," he alleges, "have been denominated conjunctively Universales, as has been done by Dr Macbride. But this," he adds, "would have destroyed the general casting of the ar