58 Veterinary Medicine. 



thsse parts fail to develop naturally and to build up good tissue ; 

 they become fatty, die, and together with the tissue in which 

 they lie, break down and pass off as a pulpy debris. Thus the 

 sore constantly deepens and widens, or at least refuses to contract 

 and heal. It is usually the result of bacterial infection. 



Gangrene or death of a part is another effect of inflammation. 

 It results usually from the cutting off of the blood-supply through 

 the obstruction of the blood-vessels ; by the pressure of excessive 

 exudation in unyielding structures, as in bone, or under the hoof ; 

 by implication of the inner coats of the blood-vessels in the in- 

 flammation, when the contained blood will clot and obstruct 

 them ; or by blocking with the blood-clots that have been formed 

 at a distance and washed on in the blood-current to be arrested 

 when they reach vessels too small to admit them. lyike suppura- 

 tion, gangrene is associated with and often caused by a bacterial 

 growth. The dead mass remains as an irritant, and is slowly 

 separated by the formation around it of embryonal tissue, granu- 

 lations and pus. A second form is molccnlar gangrene, in which 

 the cells and minute elements of the tissue die, and are cast off, 

 leading to phagedenic (eating, extending) sores, as noted above 

 under Ulceration. When gangrene occurs on an exposed surface, 

 that may be altered from the normal color into shades of yellow, 

 brown, green, red, or black, according to the amount of blood and 

 the stage of decomposition, and may be cut without pain, if the 

 subjacent parts are not pressed upon ; it may be soft, may pit on 

 pressure, may crackle under the hand from the evolved gases of 

 decomposition, and may be covered with blisters (^phlyctenai) with 

 red, grumous liquid contents {inoist gangrened ; again, it may be 

 white, as after freezing, or it may be dark-colored, dry, and 

 horny, as from ergoti.sm {dry gangrene^. 



