_Entropion_, or inversion, consists in the turning in of the tarsal margins of the lids, and generally takes place during inflammation and swelling of the conjunctival lining of the lid. During violent inflammation of the lid the conjunctiva and integuments are much swollen, and bulge out externally; by the projection the margin is forced mechanically towards the ball, and entropion takes place. But in this state of matters, should the lid be by any chance everted, and not replaced, then the bulging is from the conjunctival surface, and prevents the margin from regaining its former site, and permanent eversion or ectropion occurs. In fact, inversion and eversion, like phymosis and paraphymosis, exist from the same parts being put in different relation to each other. More permanent entropion is caused by the contraction which follows removal of tumours from the under surface of the lids, or destruction of large portions of the conjunctiva. The disease is most frequently met with in the upper lid. _Trichiasis_ consists in a vicious bend of the eyelashes, or in a supernumerary growth in the rows or numbers of individual cilia, whereby they are inverted, and sweep the surface of the conjunctiva covering the cornea; thus great distress is caused by the friction of the hairs and edge of the lid on the sensible surface of the eyeball, and inflammation is frequently kindled and kept up by the continued irritation; it is accompanied by its usual distressing symptoms when seated in that organ, and too often followed by a greater or less number of untoward consequences. Sometimes only one or two hairs are at fault; in other instances, the half of the eyelash grows inwards; and sometimes there is a double row of cilia; one set being in the usual position, while the other projects against the eyeball. If proper means are not taken to remedy the evil, and moderate the irritation which it produces, the cornea becomes thickened and changed in structure; and vision, at first impaired and indistinct, may be entirely lost. The symptoms may be for a time palliated by plucking out the faulty hairs, abstracting blood from the loaded vessels, and subsequently using ointments or collyria,—the best of which, perhaps, is the solution of nitrate of silver. In some cases it may be necessary to employ counter-irritation, as blistering the nape of the neck; and in all the general health must be strictly attended to. Other means may be required, and will be mentioned when treating of chronic ophthalmia. The permanent cure of the disease is effected either by removal or by destruction of the roots of the cilia. The whole edge of the eyelid, or the offending part of it, is removed with a sharp narrow bistoury, the operator steadying the parts by laying hold of the cilia with the fingers of his left hand. It is necessary to remove the mere edge only, the cilia and their roots, and not the whole of the tarsal cartilage, as has been proposed.