CATAPULTA, 



CATARACT. 



663 



applied cold and generally contain a preparation of lead ; for the latter 

 they are of different degrees of temperature. When it is intended to 

 hasten the progress of inflammation so as to lead to suppuration, 

 poultices should be of as high a temperature as the part will bear, but 

 of a lower temperature when they are used as mere emollients. The 

 material of which the poultice is made influences its action, but those 

 are best which have the power of retaining heat and moisture for the 

 greatest length of time. The meal of linseed, especially if the oil has 

 not been expressed previous to reducing the seeds to powder, is the 

 best for all common purposes ; but John Hunter complained that this, 

 and all poultices, were generally made too thin. For application to a 

 limited space, such as the lip or eyelid, a roasted apple or fig is best ; 

 and a roasted onion is the most suitable application to a boil. Poultices 

 are seldom changed with sufficient frequency. A fresh poultice should 

 always be applied before the one before it has become cold, when the 

 object in to expedite the maturation of a swelling and bring about 

 suppuration. When the surface is broken and suppuration going on, 

 it is not necessary to change the poultice so frequently, as it is desira- 

 ble to exclude the air as much as possible. To cleanse ulcers, the 

 carrot poultice is a good application, and when there is much irritability 

 or foetor, the yeast poultice, or one containing charcoal finely powdered 

 are good, but chloride of soda or zinc is better than either. Manga- 

 nate of potash is also good. [DISINFECTANTS.] The face of a poultice 

 is often coated with oil, and sometimes powdered camphor or red bark 

 may be sprinkled on it, according to the object in view. 



CATAPULTA. [ARTILLERY.] 



CATARACT (Gr. <raTo$</cT>)j, in its most common sense, " a fall of 

 wter over steep rocks," also, " a door that shuts to," " a bolt, barrier, 

 or obstruction," from KaTaip^-fdiy-vo/u, to break down or interrupt), is 

 an opacity of the crystalline lens or its capsule, which obstructs the 

 transmission of light to the retina, and, according to its degree, impairs 

 or destroys the sight. 



To understand its nature, and the means adopted for its cure, the 

 following anatomical facts must be borne in mind. The cornea or front 

 of the eyeball is a tough, transparent, and slightly protuberant shell, 

 firmly united to the sclerotic coat or white part of the eye. Immedi- 

 ately behind the cornea is a space filled by a watery fluid, the aqueous 

 humour, in which the coloured ait is suspended like a screen. This 

 membrane, attached by its outer edge to the sclerotic near its junction 

 with the cornea, has the power of contraction and expansion, so as to 

 limit the admission of light through its central opening called the 

 pupil to the amount best adapted for vision. Behind the iris and 

 nearly touching it is the crystalline lens, inclosed in a transparent 

 membranous capsule, which is attached to what are called the ciliary 

 processes behind the external border of the iris. The narrow interval 

 between the lens and urea or posterior surface of the iris is called the 

 posterior chamber ; the more ample space which separates the iris from 

 the corned is called the anterior chamber. The crystalline is a trans- 

 parent sticky substance of high refracting power, firmer towards the 

 centre or nucleus, more soft as it approaches the capsule, to which it 

 very slightly adheres. It is nearly flat in front, and swells out behind 

 into a considerable convexity imbedded in a corresponding hollow of 

 the ritreout humour. This fluid fills up the remaining space in the 

 globe ; it is inclosed in a pellucid membrane termed the hyaloid, and 

 seems to consist of water contained in the interstices of a fine cellular 

 structure, which, dividing it into separate portions, gives it a semi- 

 gelatinous consistence. The delicate expansion of the optic nerve 

 called the retina is placed, like a cup with the concavity forwards, 

 immediately behind the hyaloid, the edges advancing as far as the 

 attachment of the capsule of the lens ; it consequently incloses the 

 whole of the vitreous humour. 



The disease we are now in a condition to describe is divided into 

 true and tpnrioui cataract. The latter term is applied to an obstruction 

 which arises from an opaque film of purulent lymph thrown out by 

 inflammation between the uvea and the capsule, often producing ad- 

 hesion between these parts, and passing like a gauze blind across the 

 pupil. The usual means which control inflammation in other cases 

 may be used in this, and sometimes effect a cure, but no operation is 

 applicable to it ; it may arise from injury, and occurs occasionally in 

 gout and rheumatism, and in some forms of secondary syphilis. The 

 ancients appear to have considered all cataracts to be of this nature. 



True cataract is of three kinds : lenticular, when the opacity is con- 

 fined to the lens ; captular, when the capsule only is affected ; and 

 niji/mlo-lentieular, when both structures participate in the disease. 

 The term, when used simply, is to be understood of the lens itself. 



Lenticular cataract. An important practical division of this com- 

 plaint is into the hard and soft kinds. The former is the most fre- 

 quent, and is the variety visually met with in advancing age. Though 

 called hard for the purpose of distinction, it may have any consistence, 

 from that which is natural to the part, or less, to the tenacity of wax. 

 The opacity generally begins in the nucleus behind the centre of the 

 pupil, and is at first of a bluish white colour, like milk and water. 

 This gradually spreads towards the circumference, the nucleus in the 

 mean time assuming an amber-coloured or brownish hue, which some- 

 times becomes as dark as mahogany, and may extend through the 

 whole lens. The firmness of the cataract is found to bear a close 

 relation to the depth of the tint. Both eyes may be affected at once, 

 V.'it hard cataract more commonly begins in one eye; and after a 



certain time, from a few months to several years, the other becomes 

 affected in the same manner, and all useful vision is thus eventually 

 destroyed. lu this kind of cataract the lens is almost always diminished 

 in bulk, so that upon examination it may be seen to lie at some 

 distance behind the pupil, the movements of which remain free and 

 unembarrassed. 



Soft cataract is more frequently single, and prevails in childhood, 

 and the middle period of life. In this form of the complaint the lens, 

 instead of shrinking, commonly enlarges, so as to obliterate the pos- 

 terior chamber, and press the iris forward towards the cornea. Its 

 texture is everywhere changed and softened : it may be converted into 

 a turbid fluid, in which case the more opaque particles are sometimes 

 observed to subside during rest ; or it may have the consistence of 

 soft cheese. The opacity, often streaked and mottled at first, is also 

 general from the commencement, and is found to occupy the whole 

 pupil, even when dilated to the utmost by artificial means. The dis- 

 coloration varies in shade from a mere cloud to the whiteness of milk ; 

 and in the latter case the light is more completely intercepted than by 

 the darkest hard cataract, which always retains a degree of horny 

 transparency, admitting, for instance, the distinction of shade from 

 sunshine ; whereas, in the most opaque soft cataract light can barely 

 be distinguished from darkness. 



There is a kind of central opacity more allied to the soft thau the 

 hard species, in which the affection is confined to the nucleus, and 

 sometimes circumscribed to a mere speck in its centre, the rest of the 

 lens remaining transparent. This affection is most frequently met 

 with in infancy, if it be not absolutely confined to that age. 



Capsular or membranous cataract commonly appears in specks or 

 streaks of a pearly or chalk-white colour, without the bluish tint 

 which prevails iu the early stages of both the former kinds, and more 

 frequently affects the anterior layer of the capsule thau the posterior. 

 In the former situation it is close to the pupil, and is plainly convex ; 

 in the latter it is concave, but it is not so readily distinguished, as it 

 lies deeper and is seen through the lens, itself usually opaque at the 

 same time : indeed some have doubted the separate existence of 

 opacity in the posterior layer of the capsule, and it is certainly by no 

 means so frequent as in the anterior layer. 



Capaulo-lentifular cataract, or that in which both structures are im- 

 plicated, is much more common. In such cases the lens is usually iu 

 the softened state already described. Congenital cataracts are gene- 

 rally of this nature ; the opacity, if not central, being uniformly 

 diffused, and the consistence never greater, and usually much less 

 than hi the healthy state. It frequently prevails among members of 

 the same family ; and has a peculiarity which renders an early per- 

 formance of the operation of essential importance. This consists in a 

 constant rolling and unsteady motion of the eye-ball, which may 

 become habitual, and preclude the patient from ever acquiring the 

 power of directing the eyes at will towards an object. The capsular 

 varieties, especially those which commence in the .anterior layer, are 

 more frequently the result of injury, and complicated with inflamma- 

 tory conditions of the constitution or of the eye itself, than those in 

 which the opacity is confined to the lens. These last, especially the 

 hard cataracts of advanced life, are often strictly local affections, and 

 can neither be classed with inflammatory disorders, nor ^traced to any 

 constitutional cause. 



The symptoms experienced by a person affected with cataract may 

 readily be imagined. The symptom first perceived is a dim haziness 

 of sight, as if a mist or a thin veil were interposed between the object 

 and the eye. The obscurity is greatest in direct vision; in hard 

 cataract, because the opacity is originally central ; in soft, because the 

 direct rays pass through the thickest part of the lens, while those 

 which enter laterally are transmitted nearer to the edge, which is com- 

 paratively thin. The sight is better, for the same reason, in weak 

 light, and with the back turned to the window, than in strong light : 

 for the pupil in the latter case is contracted, and permits the passage 

 of the rays only through the middle of the lens. Hence also the 

 advantage derived in all coses from dropping the juice of the bella- 

 donna or deadly nightshade into the eye, which with some other 

 sedative vegetable poisons, has the remarkable property of dilating the 

 pupil by some specific action on the iris independently of the retina. 

 It is a curious circumstance that this effect is not impaired by repeated 

 applications. 



None of the varieties of true cataract are subject to the influence of 

 any known medicinal remedy, whatever may have been put forward to 

 the contrary to serve interested purposes : nor is it at all likely that 

 any remedy exists with powers capable of acting upon parts so obscurely 

 organised, and so completely out of the course of the circulation. No 

 vessels have ever been discovered in the lens under any condition of 

 that part ; and it is probably as little endowed with vitality as the 

 hair and nails. Consequently, all the palliation the case admits of is 

 limited to the local application of belladonna, attention to the general 

 state of the health, and care in removing the inflammatory symptoms, 

 with which, as we have seen, it is sometimes complicated. A radical 

 cure can only be brought about by the actual removal of the cataract. 



Much difference of opinion has existed as to the most eligible way of 

 effecting this object ; but it is now well understood that each of the 

 methods proposed may be the best in its turn, and that the point can 

 only be determined by the circumstances of the particular case. 



