52 SURGICAL APPLIED ANATOMY. [Chap. iv. 



few parts of the body that may be the seat of mela- 

 notic growths. These growths are sarcomatous tumours 

 containing a large amount of pigment, and occur only 

 where pigment cells are found. In the choroid coat 

 pigment cells are very abundant. The iris is, from 

 its great vascularity, very easily inflamed. From its 

 relations to the cornea and sclerotic it happens that 

 inflammation in those tunics can spread without 

 difficulty to the iris. On the other hand, the vessels 

 of the iris and choroid are so intimately related that 

 inflammations set up in the iris itself have every in- 

 ducement to spread to the choroidal tuuic. When 

 the iris is inflamed its colour becomes altered, owing 

 to the congestion of the part and to the effusion of 

 lymph and serum that takes place in its substance. 

 The swelling to which it becomes subject, together 

 with the effusion, produce a blurring of its delicate 

 reticulated structure, as seen through the cornea. 

 Owing also to the swollen condition of the little mem- 

 brane, the pupil becomes encroached on, and appears 

 to be contracted, while the movements of the mem- 

 brane are necessarily rendered very sluggish. If it be 

 remembered that the greater part of the posterior 

 surface of the iris is in actual contact with the lens 

 capsule, it will be understood that inflammatory ad- 

 hesions may readily take place between the two parts 

 (Mg. 10). After iritis, therefore, it is common to find 

 the posterior surface of the iris (most often its 

 pupillary margin) adherent to the lens capsule by 

 bands of lymph, either entirely or in one or more 

 different points. Such adhesions constitute posterior 

 synechiae, the term anterior synechia? being applied to 

 adhesions between the iris and the cornea. In iritis 

 also the lens may become involved, and the condition 

 of secondary or inflammatory cataract be produced. 

 The iris is not very closely attached at its insertion. 

 Thus, in cases of injury to the eye, it may be torn 



