374 ULCERATION OF PEYER'S PATCHES 



changes formerly described, in a more characteristic manner. 

 As the elevation increases, a change begins to take place on 

 the elevated surface. This change may be partial that is to 

 say, it may take place sooner on some parts of the patch than 

 on others ; but generally it extends over the whole surface, and 

 is bounded by a line situated from a 10th to a 16th of an 

 inch from the edge of the patch. The change itself consists 

 in the surface beginning to alter in colour, becoming dirty- 

 yellow or grey, and assuming a peculiar undulating or con- 

 torted surface, like a bit of leather seared with a hot iron. 

 The villi have now in a great measure disappeared, but the 

 orifices, or rather the circular folds or pits, in which are 

 situated the vesicles, are still visible. At last the confines of 

 the changed portion of the patch are rendered evident by a 

 groove apparently produced by ulceration, which, appearing 

 here and there on these confines, at last extends all round, 

 and indicates some change about to take place in the whole 

 arrangement of the parts. 



In the third stage, the groove just described makes its way 

 into the tissues ; and as it does so, the healthy but elevated 

 mucous membrane on its external edge gradually everts 

 itself, as if by the upward pressure of the matter beneath it. 

 While this is going on, the edges and surface of the altered 

 portion become more rugged, and their former character 

 somewhat obscured. The altered portion, which now assumes 

 very much the appearance of a slough tinged with intestinal 

 matters, becomes more and more detached from the surface 

 to which it adheres. When the mass is gently raised under 

 water, it may be observed that its attached surface sends 

 processes down into the cellular membrane beneath ; and if 

 these processes be carefully drawn out, they will be found to 

 correspond each with one of the original vesicles of the patch. 

 When detached in this manner, they leave on the surface to 

 which they adhered, dimples, or rather pits, which may be 



