Page:Handbook of Ophthalmology (3rd edition).djvu/309

Rh down to the lower margin of the cornea. But upon examination with focal illumination, it is impossible to say whether it lies before or behind the membrane. The structure of the deeper layers of the cornea is so loose, and their connection with the membrane of Descemet is so slight, that the wandering downward of the pus-cells, assisted by gravity, meets with but little obstruction. But when the pus has once reached the membrane of Descemet, it can easily pass through the openings of the ligamentum pectinatura into the anterior chamber. It is possible that the pus may settle in this manner, but the question is, does it actually do so? According to Horner's observations, this process takes place on the posterior surface of the membrane of Descemet. The pus-cells from the corneal ulcer penetrate the membrane of Descemet, accumulate upon its posterior surface, and finally sink downward. Evidently an accumulation of pus in the corneal substance could not immediately rise and discharge itself with the aqueous humor when a puncture is made in the cornea at some distance from it in the horizontal direction. At least the walls of the channels through which it had sunk would remain infiltrated and would show a distinct cloudiness. If now, after paracentesis of the cornea, nothing remain but the diffuse clouding of the anterior layers, we are forced to the conclusion that the appearances which seemed to be in the corneal substance, really were in the anterior chamber. Experiments upon the eyes of guinea-pigs and rabbits have furnished results which confirm this view.

Iritis is a complication which generally occurs quite early and is seldom absent. The change in the color of the iris, caused by it, cannot always be well seen, on account of the clouding of the cornea, but can generally be detected, at least at the margin of the pupil. The diagnosis is confirmed by the posterior synechiæ, which are made to appear by the action of atropine. Often there are, simultaneously, especially near the lower margin of the pupil, semi-transparent flakes floating in the aqueous humor, which present exactly the appearance of coagulated fibrin. Frequently, in consequence of the purulent infiltration, the tissue of the iris, as appears in the operation of iridectomy, is exceedingly weak and brittle.