MORTIFICATION. 59 



The fiaal act in the separation of dead tissue is that of 

 ulceration of portions of living tissue, which are in immediate 

 contact -with the dead. A groove is formed by this ulceration, 

 which circumscribes and entrenches the dead part, and then, 

 gradually deepening and converging, undermines it, till, reach- 

 ing its centre, the separation is complete, 'and the slough falls 

 cfi", or is dislodged by the discharge of the ulcerated living 

 surface. Concomitant with tliis process of destruction, one of 

 repair is set up ; as the ulcerated groove deepens, so do granu- 

 lation cells rise from its surface, so that, as one miglit say, that 

 which was yesterday ulcerating is to-day graniilating ; and thusj 

 very soon after the slough has separated, the whole surface of 

 the living part, from which it \vas detached, is covered with 

 granulations, and proceeds like an ordinary ulcer towards healing. 

 There is one peculiarity in mortification, namely, mortijlcation 

 "by contact. Thus a spot of mortification of the size of a five- 

 shilling piece is discovered upon a portion of intestine, sur- 

 rounded by perfectly healthy structures, until^ the portion of 

 the intestine in immediate contact with the gangrenous spot 

 is examined. Tlu's will be found to be gangrenous also, 

 although, when divested of its convolutions, it may be several 

 feet from the originally mortified spot, the intervening lengtl^ 

 of gat being free from mortification. 



