EXTRAVASATION

is the escape of a fluid from the ve els which naturally contain it into the surrounding ti ues. When a blow is given with o blunt instrument, the smaller blood ve els beneath the skin are ruptured, and blood is then extravasated into the surrounding parts, hence the colour of a bruise or black eye. Rupture of the bladder causes extravasation of urine. EYE is the organ of vision placed in a socket in the skull known as the orbit. Between the orbit and the eye is a padding of fat and certain muscles for the movement of the eye the raising of the eyelid. The eye communicates with the brain by the Sap nerve which pa es through an oy aa in the bony wall of tho orbit behind the eye. The blood supply to the eye consists of the ophthalmic arte and veins. These ve els also pa from within the skull through apertures in the bony wall of the orbit to the eye. The eye consists of a transparent coat in front known as the cornea and of a tough opaque coat behind, the white of the eye or sclerotic. Dividing the eye into an anterior and a posterior chamber and attached just at the junction of the cornea and sclerotic is the onoe lens, which isa zererent double convex lens, that focu es light on to the back of the eye. Within the sclerotic are two inner coats, known respectively as the choroid and the retina. The choroid contains hlood-ve els and is black so that ee — that reaches it is not reflected. The retina con sensory organs which communicate with the optic nerve. The space botween the lens and the cornea, known as the anterior chamber, contains a watory fluid, the aqueous fluid, whilst the space between tho lens and the retina is ~ filled with a transparent jelly known as the vitreous, which eo the eye its shape and elastic consistency. In = of the lens is = pe muscular membrane—the or coloured part of the eye—presenting in ite centre 8 circular hole—the pupil—which looks black because the interior of the eye is visible Gro e it. To keep the cornea from becoming ue ust settling on it, it is continually washed by the tears nae by the eyolids, which het Aiea seconds and thus polish the cornea. Vision is effected by the following series of steps:— Light is focu ed in pa ing through the cornea, the aqueous fluid, the crystal lino lens and the vitreous, and finally is thrown on tho retina, where it forms an inverted picture of the object from which itcame. The retina is stimulated by the light, and its different i aro stimulated differently by tho Ce ee the pctare which is focu ed on it. Such erences are naferred, not as light, but as norve Sea along the optic nerve to that part of the brain w {is concerned with vision, and although the picture on the retina is inverted, the mental impre ion produced is erect. In focu ing light the cornea is the most erful agent. The use of the ust is to enable objects at different distances to be accurately focu ed. Such okay Beg the camera is done by altering the distance between the lens and the late without change Oe lens. In the eye the distance fren the lens and plate (retina) is constant and the lens is altered in rx, tears The nearer an object tho more convex the has to be. Such alteration is effected by a ring of little muscles placed round the edge of the lens, and the proce is termed ‘ accommodation.” A coom mod at i on for objects nearer to the eye than ten inches is effected with difficulty. Tho iris or coloured part of the eye oe rap the size of the hole in its centre through which light is admitted, and corresponds to the diaphragm of optical instruments. In strong light the iris contracts the pupil and shuts off light and vice verea in faint light; and in looking at a near object it also shuts of all light except that near the centre of the pupil, the purpose of which is to produce a more sharply focu ed image on tho retina. It is thus clear that the eye is an optical instrument very similar in principle to optical instruments of human invention, though infinitely more perfect in its power of rapid adaptation. The health of tho eye is often maintained when the general health is much disturbed; there are, however, ra abnormal conditions of the eye, the chief of which wo will now briefly Any fe body in th best dealt with by closing Any /oreign body in the oye is best dealt wi closi both ayaa and rubbing the normal one, a flow of, tears is thus induced, which often atte tice the foreign body. If this fails, the lower lid should be drawn down, and if the body can be seen, it should be touched with the tip of a clean handkerchief or piece of blotting paper. Eversion of the upper lid, that is =e it 5 4 expose the inner surface, requires practice and is t not attempted. Splinters of iron, grit, etc., embedded in the cornea, should not be touched till a doctor is obtaincd, but a drop of castor oil should be applied to the inside of the lower eyelid drawn down for the purpose, and the affected eye should be a ip up to prevent tho sufferer cor, damage by sea Be and in children tho hands should be secured also. Lime in the eye is best treated by riety don oo oil or weak vinegar and water. Water alone is treatment. Ulcer of the cornea is common, due either to injury or to constitutional causes. In healing, ulcers leave an opacity on the cornea, which often takes years to clear up. By perseverance, however, much can be done. Special spectacles are generally required. The treatment from the first must be in medical hands. The membrane which lines the inner side of the eye-lids and connects them with the eye is the conjunctiva, inflammation of which is conjunctivitis. Of this there are many forms, ©.g- (1) simple, (2) purulent, and (3) granular. (1) The simple form is ect up by ai causes, such as @ oreign body in the eye, a chill, eto. The symptoms produced are smarting in the eye as though something was in it, pain on looking at the light, discharge which gams the lids together daring the night, whilst the eye itself is bloodshot. The treatment is to syringe tho eye twice oy with warm boric lotion and to smear the oot of the lids with cold cream, the eyes should be protected from strong light, and in the severer cases small pads of lint or linen ed in iced water should be sae eens whilst all rubbing with the tn dese carefully avoided. (2) “ Parulent oph ia," or the ophthalmia of the new-born infant, causes many cases of blindne pray the poor. In such cases conjunctivitis begins within five days of birth. Tho whee halal Macey, the eyelids, » mattery discharge and burning pain; tho cornea may be destroyed by ulcoration endl blindne result, Until the [s. 362]