INTRODUCTION. 33 



part of the body it dies^ and chemical forces are enabled 

 to bring about its decomposition. Sometimes the blood is 

 not permitted entry into a part through obstruction of 

 the arteries of supply ; then dry gangrene may take 

 place, which consists in the drying up of the tissues, their 

 diminution in size, and complete loss of all vital pro- 

 perties. The dry, mummified mass remains as a foreign 

 body, perhaps becoming invested by a coating of lymph. 

 This has been observed in the case of pleuro-pneumonic 

 lung. When a part is the seat of moist gangrene, it be- 

 comes very dark in colour, pits on pressure, swells in con- 

 sequence of the liberation of gases by decomposition and 

 their accumulation beneath the epidermis/which they raise 

 in spots forming hlehs. A sanious discharge with foetid 

 odour takes place from the surface of the mass, which is 

 sodden with a similar material, and has lost all sensation 

 and other physiological processes, and is very cold. 

 Moist gangrene is more frequent than the dry form, 

 and depends on impeded return of blood. A part 

 which has thus undergone mortification is removed by 

 sloughing. Salutary inflammation sets in on the line of 

 junction of the dead with the living parts, and here con- 

 solidation by exudation takes place to prevent infiltration 

 of gangrenous material into healthy parts. Suppuration 

 of this consolidated layer occurs, and thus the dead mass 

 is thrown off. Molar death of bony tissue is termed 

 Necrosis, and the portion of removed material is a 

 Sequestrum. During this process of gangrene the con- 

 stitutional powers are much diminished, the pulse being 

 small and weak and frequent, and the strength rapidly 

 failing. The animal has a wild, apprehensive look, and is 

 very restless ; cold sweats bedew the skin, and there is a 

 gangrenous odour. Sudden cessation of pain often 

 announces this result of inflammation. The termination of 

 the case will be favorable or otherwise, according as the 

 strength of the body proves equal to removal of the slough 

 or the reverse. In old age senile gangrene may occur as a 

 result of deficiency of vital energy, affecting especially those 

 parts most remote from the central organ of circulation. 



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