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CLASS IV.

ORDER II.

Esthética.

affecting the

Sauvages, and after him Sagar and Cullen, have applied dysæsthesia to a morbid state of the corporeal senses generally; whence anesthesia should in their hands have Diseases expressed atony or total inactivity of these senses gene- sensation. rally. But while dysæsthesiæ extends to all the senses, Sauvages and Sagar. anææsthesia is by the same writers limited to the single sense of touch; with no small perplexity to the young student.

In the Physiological Proem to the present class we have taken so full a survey of the connexion which exists between the brain and the corporeal senses by means of the nerves, that it is not necessary to say more upon the subject at present: and I shall only therefore further observe in these preliminary remarks that where one of the senses is deficient, and especially where naturally deficient, the rest have very frequently been found in a more than ordinary degree of vigour and acuteness; as though the sensorial power were primarily derived from a common source, and the proportion belonging to the organ, whose outlet is invalid, were distributed among the other organs*.

a

The genera, under the order before us, are taken in regular series from the corporeal senses themselves in a state of morbid action, and are in number six of which the first five are derived from the five external senses, and the last from a diseased state of particular branches of the nerves distributed over the frame generally for the common and pleasureable feeling of health in the different organs through which they are dispersed.

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Where one sense de

ficient,

others often peculiarly

vigorous.

Order of the

ensuing

genera.

Trinckhusius, De Cæcis sapientiâ ac eruditione, claris mirisque cæcorum

quorundam actionibus. Geræ, 1762. Meckren. Observ. Med. Chir. cap. xx.

GEN. I. Origin of

GENUS I.

PAROPSIS.

Morbid Sight.

SENSE OF SIGHT VITIATED OR LOST.

PAROPSIS is literally "diseased or depraved vision," from the generic aga, male, and os, visus; as paracusis, "diseased or depraved hearing," from açà, and άxovń.

term.

Diseases of

the eyes unneces

sarily multiplied.

The ophthalmic monographists, by making every variety of affection a distinct disease, have most unmercifully enlarged the list under this genus*. To say nothing of Campiani, Taylor has in this manner mustered them at two hundred and forty three†, while Plenck has contrived to multiply them to nearly six hundred‡. Upon a comprehensive view of the subject, it will, I think, be found that this formidable number may be reduced to the twelve species following:

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Campiani, Raggionamenti sopra tutti i Mali degli Occhi descritti, &c.

Genoa, 1759.

+ Catalogue of two hundred and forty three diseases of the Eyes. Edin.

Vol. 1749.

Doctrina de Morbis Oculorum. Svo. Vienn. 2d Ed. 1783.

Most of these fall rather within the province of the ophthalmic surgeon than of the physician; but, as their general nature ought to be known to every practitioner, we shall proceed to give a glance at each of them in their order. The maladies of the eye dependant on inflammation, and constituting ophthalmy, have been already treated of in Class III, Order II, HEMATICA, PHLOGOTICA.

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SPECIES I.

PAROPSIS LUCIFUGA.

Night-Sight.

VISION PAINFULLY ACUTE IN A STRONG LIGHT; BUT

CLEAR AND PLEASANT IN A DEEP SHADE OR THE DUSK
OF THE EVENING.

GEN. I. SPEC. I. Specific name justi

fied, as being a new

term.

arising

names

nyctalopia

THE specific term lucifuga is so distinct as at once to point out the general nature of the affection while constituting a very prominent symptom. The author, however, has found a necessity for introducing this new name, not more from its own clearness than from the confusion which has taken place among earlier writers in distinguish- Confusion ing the disease by two directly opposite terms, nyctalopia from the and hemeralopia, according as these terms have been former used in a literal or a technical and implied sense. The Greeks called it by the former name, literally night-sight, and hemein consequence of the person labouring under it being ralopia. only able to see at night, or in a deep shade; while nyctalopia has been used by most modern writers in the opposite sense of night-sight-ache, agreeably to the technical or implied meaning of opia when employed patholologically; in which case it always imports diseased vision, as though a contraction of the term paropia or paropsis: whence nyctalopia has necessarily been made to import day-sight, instead of night-sight, or that imperfection of vision in which the eye can only see in the day or whenever there is a strong light. And hence hemeralopia, the

Illustrated.

GEN. I.

SPEC. I.

Paropsis

lucifuga.

Nightsight.

Luscitas of

Beer.
Exposure

to too

strong a light a cause: and why.

Perpetual nictitation.

Frequent

lian pea

sants.

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opposite to nyctalopia, has been used, with the same confusion and contradiction of signification; by the Greeks importing day-sight, being taken naturally or literally; by the moderns day-sight-ache, and consequently nightsight, being taken technically or by implication; and hence Sauvages," Græcis hemeralopia; neotericis nyctalopia." It is the luscitas of Beer *.

The disease is dependant upon a peculiar irritability of the retina, produced by two very different causes: a sudden exposure to a stronger light than the eye has been wont to sustain; and a deficiency of the black pigment which lines the choroid tunic. If the iris be weak and torpid it is enlarged; if strong and contractile, diminished.

From the first cause this disease is common to those who live almost constantly in dark caverns or chambers, as mines, dungeons or other prisons; or who have recently had a cataract depressed or extracted, the growth of which has still more effectually excluded the light from falling on the retina. And in all these cases we find it accompanied with a perpetual nictitation, from the sympathy which prevails between the retina and the orbicular muscles of the palpebræ.

Ramazzini asserts that this complaint is common to among Ita- the peasants of Italy who are employed in agriculture; but in whom he is able to trace no other peculiarity than a considerable enlargement of the pupilt. It is not Explained. difficult perhaps to assign a reason for such an affection among these people, though Ramazzini is silent upon the subject. The sky of Italy is peculiarly bright, its atmosphere peculiarly clear, and its temperature relaxingly The peasants of Italy, therefore, are exposed to the joint operation of almost every cause that can produce habitual debility in the iris, and irritability in the retina. And we find these causes acting with renewed power at the time when the disease chiefly makes its attack, which

Effects.

warm.

* Lahre von der Augenkrankheiten, als Leitfaden zu seinen öffentlichen Vorlesungen entworfen. Qwey Bande, 8vo. Wien. 1817.

+ De Morbis Artificum, &c.

GEN. I.
SPEC. I.

Paropsis

moved.

we are told is on the return of spring, or rather at the vernal equinox, when a double flood of day breaks on them. And such is the dimness it produces that the lucifuga. Nightpeasants lose their way in the fields in the glare of noon; sight. but on the approach of night, they are again able to see distinctly. It is hence necessary for them to keep for How resome weeks in the shade or in comparative darkness, till the eyes recover their proper tone: and the weakness, and consequently the disease, subsides. And hence Ramazzini tells us that in the course of the succeeding month, or, in other words, after they have taken due care of themselves, the peasants recover their sight. The glare of the Produced by sun, in tropical regions, and especially where reflected an intense glare. from bright chalk-hills, has often produced the same effect

pigment

a cause:

mon to Al

binoes.

A deficiency of the black pigment is occasionally found Deficiency in persons of a fair complexion and light hair; and, as the of black retina is hereby deprived of the natural shade that softens the light in its descent upon this very sensible membrane, and why. its morbid irritability is not to be wondered at. Albinoes, Hence comwho are without the common pigment that lies between the cuticle and cutis in other persons, are always deficient in this also; and hence are peculiarly subject to the present disease. In old persons the same deficiency is sometimes traced, but without painful vision: for at this time of life the optic nerve is become more obtuse. In horses this want of pigment constitutes what is called a wall-eye. The disease is occasionally found as a symptom in ophthalmy, various other irritations of the optic nerve, and hydrops capitis; and sometimes terminates in amaurosis*.

Acuteness of night-vision is natural to various animals that prowl in the dark; as cats, lynxes, lions, and perhaps, all the feline genus; which save their eyes from the pain produced by broad day-light, by a closer contraction of their irids than mankind are able to effect; expanding them gradually as the night shuts in, till by

Piso, De Med. Brasil, Lib. II.

Sometimes

found in

old age. Constitutes the wall

eye in Found as a symptom

horses.

in various diseases.

Natural to quadrupeds that prowl at night.

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