Imatges de pÓgina
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Mountain, which is three thousand six hundred feet high, and the upper part of which rises perpendicularly at the distance of about a mile from Cape Town, every noise made in the town, and even the word of command on the parade, may be distinctly heard. Shakspeare therefore is probably more correct when he describes the crows and cloughs from Dover cliff to shew scarce so gross as beetles,' than when he says

the murmuring surge
That on th' unnumbered idle pebbles chafe,

Can scarce be heard so high.' The volume concludes with some account of the attempts at working the gold and silver mines of the Caraccas, which were soon abandoned from the slender indications of these metals, and the high price of labour; but M. de Humboldt thinks that the question whether the province of Venezuela possesses mines worthy of being worked is by no means decided ; and that although in countries where labour is dearer, the cultivation of the soil demands unquestionably the first care of government, the example of New Spain sufficiently proves that the working of metals does not always injure the progress of agricultural industry. The highest cultivated plains of Mexico, (he says,) those which recal to the recollection of travellers the most beautiful fields of France and the south of Germany, extend from Silao towards the Villa de Leon : they border on the mines of Guanaxuato, which alone produce the sixth part of all the silver of the New World.'

We have been copious in our extracts, in order more fully to exhibit M. de Humboldt's manner of treating his subjects. Being less scientific than the former part of the narrative, this volume is better adapted for the general reader; and, as M. de Humboldt knows so well to communicate an interest to every subject which comes under his view, we have very little doubt that his remaining volumes, which will conduct his readers along the Oronoco, the Cordilleras of the Andes, and the elevated plains of Mexico, will rise in interest with the importance and grandeur of his subjecct.

ART. VII. A practical Inquiry into the Causes of the frequent

Failure of the Operations of Depression, and of the Extraction of the Cataract, as usually performed; with the Description of å Series of new and improved Operations, by the practice of which most of these Causes of Failure may be avoided. Illustruted by Tables of the compurative success of the new and old

modes of practice. By Sir William Adams, &c. London. 1817. THERE is less of the art of composition in this book than we

usually meet with in the present day. The title-page has in no inconsiderable degree run away with the preface--and the dedication with the subject and the supplement. The periods are,

in many instances, out of joint; the manner is too diffuse and desultory, and the propoun of the first person somewhat more frequent in its appearance than is customary in the polished reserve of modern times. With all this, however, the work has a peculiar claim to attention, and we have read it with considerable interest. Its subject is highly important; its questionable points are discussed with great candour; it is enriched with the opinions and practice of the best and most skilful authorities of every country, not ostentatiously paraded, but fairly brought forward and compared, for the purpose of stating their respective merits and defects, and of showing the necessity of some improvement in the best modes of operating for the cataract which have hitherto been devised; and it is rendered still more valuable by the author's ingenuous disclosure of the practice which he is well known to have applied with success to the blind pensioners of Greenwich Hospital, as well as in the private course of his professional engagements.

The definition of the disease called Cataract is thus given in the opening paragraph of the work:

• The term cataract is of Greek derivation, and signifies an opacity either of the crystalline lens, its capsule, or the interstitial fluid contained between the lens and capsule, which is called the Humour Morgagni, (Humor Morgagni) it having been first discovered by the eminent anatomist of that name. Cataract may exist in any of these parts separately, or they may all be at the same time opaque.' To which the author adds, (p. 4.) ' the capsule and lens are, however, much more frequently occupied by disease than the humour morgagni.'

We suspect that a simple cataract of Morgagni's interstitial fluid is rather a speculative than an actual disease; one that possibly may exist, rather than one that has been actually detected and described. Richter, so far as we are acquainted, is the only writer before Sir William Adams, who has ever noticed this species or variety; for at present we know not how to arrange it. The notice occurs, as in the volume before us, in the initiatory account of the disease, and is never touched upon or referred to afterwards. Nor do we recollect a sivgle case of the kind described as an actual occurrence in any author whatever: and hence Plenck, who has made a very free use of Richter, and followed up the diseases of the eye through little less than six hundred distinct species, (to say nothing of the numerous varieties into which each of these species is still further divided,) and who may therefore be conceived to have given all that is needful, has omitted the interstitial cataract altogether. *

It His definition being as follows.— Cataracta-est cæcitas, quæ ab opacitate lentis crystallina, vel ejus capsulæ, provenit.-Respectû sedis, quam opacitas tenet, dividitur

cataracta,

It is singular that the term cataract, though, as our author observes, of Greek derivation, and certainly of considerable antiquity, is not to be found eitber among the Greek or Roman writers; the first of whom called the disease apochysis (tóx"615) or hypochysis (úzóx1015) —and the latter suffusio, which is the name employed by Celsus. Cataracta, however, is in frequent use among the Arabian authors, and is generally supposed to have been invented by Avicenna. That we derived it from the splendid caliphat of Bagdad there can be little doubt. The term cataract, however, does not exactly signify an opucity, as is stated in the definition before us, nor disturbance or confusion of the sense of vision, as is its comnion interpretation. Cataractes, or catarrhactes, (καταράκτης Or καταρράκτης,) whence the Latin cataracta, is a genuine Greek term, importing a gate or door, or the bar which fastens it and proves an impediment to its being opened ; and, as the eyes were called by the Greek philosophers the portals or windows of the mind,

Dicere porro oculos nullam rem cernere posse,
Sed per eos aniinum ut foribus spectare reclusis,

Difficile est---
the elegant fancy of the Arabians applied the term cataracta to the
disease before us, as forming a bar or shutter to those windows
by which the mind obtains a view of external objects, or an external
world.

One of the most difficult species of cataract to detect is that of the lenticular membrane or capsule, (the second of Plenck and of Sir William Adams,) when confined to its posterior part, or that immediately behind the lens itself, and which is hence, in a very considerable degree, concealed by it. From the depth of the opacity, covered by the healthy appearance and natural brilliancy of the lens, it is not surprizing that it should have puzzled many ophthalmists of considerable practice, and been mistaken by others for an ainaurosis or gutta serena, and consequently, while admitting of cure, been abandoned as an intractable disease.

• The opacity of the anterior part of the capsule can at all times be easily distinguished; but the posterior opacity is not easily detected, and has been known to elude the careful examination of several very experienced oculists, by whom it has been mistaken for gutta serena ; and, although this species of cataract is mentioned by authors, it may be doubted whether they were, in reality, practically, aware of its existence. Indeed, without the assistance of the belladonna, or some other application capable of dilating the pupil, which class of applicacataracta, 1. In crystallinan, si ipsa lens crystallina est opaca. 2. In capsularem, quam alii membranaceam vocant, si capsulæ crystallinæ lamina anterior, vel posterior, vel utraque, opaca redditur. 3. In crystallino-capsularem, si lens crystallinia et ejus capsula sinjul opacantur.'

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tions were known to the ancient writers, but have been revived only within these few years, it is difficult, and sometimes iinpossible, lo distinguish it. Richter, Wenzel, and Scarpa, who have written so largely upon cataract, and have published cases of its varieties on which they have operated, have not recorded any instance of this remarkable species : in which the posterior part of the capsule is alone affected with opacity, while the anterior part of that membrane, and the crystalline lens, remain perfectly transparent. In this country, at least, ihere is reason to believe, that it was practically very little known previous to the publication of my work on Cataract, &c. in 1812, in which a case of this kind is detailed at length, in a gentleman who had been blind eighteen years, seven of which he had been under the care of an eminent and experienced oculist, who considered and treated the disease as Gutta Serena.'-pp. 6-8,

We have no doubt of the correctness of this statement, so far as relates to our own country, and concede to Sir William Adams the merit of having first practically called the attention of the English profession to this peculiar species of cataract, though the quotation we have just made from Plenck is a sufficient proof that the disease had been long known, and its seat distinctly laid down by writers on the continent.

It was formerly supposed, by one or two writers, that the crystalline humour has no proper capsule, and that the only membrane which invests it is a duplicature, or anterior and posterior extension of the membrane which incloses the vitreous humour, and which is commonly described by the name of tunica aranea, or membrana hyaloidea ; but it had altogether escaped our attention that this anatomical mistake, as we must still venture to call it, had been unaccountably revived within the last five years by a distinguished surgeon of this metropolis, in a passage copied by the present writer, and plausibly asserted to be little more than a transcript from Anthony Maitre-Jan's Traité des Maladies de l'Oeil. It is not necessary to enter into the subject : the anatomy of the eye is too well known in the present day to render the point for a moment questionable ; and if it were not, the cloud of authorities brought forward by Sir William Adams, in proof that the lens has a tunica propria, and that the species of cataract before us is seated in the posterior part of that tunic, would impel us to banish all hesitation whatever.

But we mention the fact for two reasons. First, because an error upon this subject is of great importance in a practical point of view ; and secondly, if the position could be sustained for a moment, that the investing membrane of the lens is nothing more than an extension of the investing membrane of the vitreous humour, no writer has bitherto explained the proper meaning of the term cataract, as technically employed, or the real nature and extent of VOL. XVIII. NO. XXXV.

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the disease it indicates; since, instead of being limited, as we believe it has been by every one, to an opacity of the lenticular chamber, or its delicate walls, it would run indefinitely into the walls and chamber of another and very distinct portion of the eye-ball, and, consequently, confound diseases that have bitherto been beld altogether discrepant and dissociate.

The cause of cataract-we mean that of the crystalline lens-bas never hitherto been satisfactorily explained. It was at one time supposed to be most frequently a result of inflammation. Our author abandons this principle upon every occasion, and adopts its opposite—that of debility of the minute vessels of the lens : in other words, we are now to read atony instead of entony as its origin.

• Indeed, it is a matter of doubt with me, whether the body of the lens is, under any circumstance, capable of taking on inflammation, although, both from disease and accident, the capsule is susceptible of it in a high degree: and I think it more probable, when opacity of the lens results from a blow upon the eye, without the capsule being ruptured, that it originates from the derangement produced in the minute vessels of the lens, which occasions the want of a sufficient supply of blood, rather than an excess of it.

* This hypothesis (for such it must be considered) seems strengthcned, by the manner in which cataract is supposed to occur in old persons, in whom the minute order of vessels, in common with those of every other part of the system, becoming obliterated, probably produces an opacity of the lens, from the want of nourishment, which, in consequence, being no longer influenced by the circulation of the blood, Joses its vitality, and becomes opake.'--p. 29.

This explanation is ingenious; yet as a cataract of the capsule produced avowedly by inflammation, in many instances extends to the body of the lens, it does not account for the means by which such extension is produced. In this case, the action seems to be one and the same-simple and continuous. But upon the hypothesis before us we are to suppose two opposite actions-excess of irritability operating on the capsule, and deficiency of irritability upon the lens ; to contemplate the one as the cause of the other, and both these opposite actions as productive of a common result.

The progress of the disease is accurately sketched in the follow

ing passage:

The first symptom of the approach of cataract is marked by a slight obscurity of vision, as if the patient was looking through a cloud, light smoke, or dirty glass, which is frequently accompanied with the appearance of black specks, cobwebs, flies, &c. flitting before his eye. At first, there is so small a change in the appearance of the crystalline lens, that no person, by examining that body, would be led to suspect the approach of cataract, as the dullness of vision perceived by the patient, I believe generally, if not always, precedes any observable change in the transparency of the lens, which frequently renders it

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