4 NECROSIS OF TISSUES. 



ism wliicli results from their genetic unity, and which we call 

 life, come to an end, than external influences assume a dominion 

 over the body similar to that which they exert over inorganic 

 substances ; in other words, the only force which still tends to 

 maintain the body in its previous form is the force of cohesion. 

 Owing, however, to the great proportion of water which enters 

 into the composition of the body, this force operates but feebly ; 

 hence death is closely followed by disintegration, which, though 

 at first gradual, proceeds at an accelerating rate until dissolution 

 is complete. So long as the body retains to some extent its out- 

 ward form, we continue to speak of it as " dead."* 



§ 8. In presence of somatic death the art of the physician is 

 powerless. We might spare ourselves the trouble of studying 

 the changes which accompany the death of the tissues, were it 

 not that single portions of the organism are liable to die, an 

 occurrence which we call necrosis, mortification, or gangrene. 



§ 9. The death of a part is not always followed by the same 

 series of anatomical changes. The variety of the causes which 

 may lead to necrosis, as well as the situation and individual 

 constitution of the necrosed parts, occasion very marked differ- 

 ences, particularly as regards the proportionate amount of blood 

 and water present, which have led to the recognition of two forms 

 of gangrene, the dry and the moist. In the ensuing sections 

 this distinction will be home in mind ; it will be shown, however, 

 that the distinction is based rather on the clinical characters and 

 coarser features of the process than on its finer anatomy. 



Note. — A large majority of the various forms of mortification may 

 be looked upon as due to a complete arrest of nutrition. Among the 

 chief conditions of undisturbed nutrition, a regular and continuous 

 supply of blood takes the foremost place. If, therefore, the quantity of 

 arterial blood which passes through any region of the body (thereby 

 becoming venous) in a unit of time should sink below the normal 

 standard, the nutrition of that region must needs suffer; should the 

 current entirely cease, nutrition must cease with it. The affected part 

 may nevertheless contain an excess of blood ; and this may be so great 



* Inorganic nature, into whose domain the constituents of the 

 organism now return, is also called "dead"; but here the term is used 

 metaphorically. In common language, the word "dead" implies that a 

 body, though still exhibiting the organic type of structure, is no longer 

 the seat of the organic functions. 



