1 82 



Necrosis. 



the surfaces of which' there is apparently always present a rich 

 variety of bacteria (pharynx, stomach and intestines). The 

 putrefactive germs may be carried from such situations by the 

 lymphatic and blood streams into the internal organs, where new 

 foci of the putrefying process result from embolism. Tissues the 

 seat of marked hsemorrhagic infiltration and those with large lymph 

 spaces, are especially likely to become gangrenous, the stagnating 

 blood and rich supply of moisture favoring the multiplication of 

 the putrefactive organisms. The discolored liquid of the decom- 

 posing part is known as putrid icJidr. 



Fig-. 20. 



Microscopic section through a necrotic area in liver of cow; tlie border of 

 the coagulated necrotic material close to the normal tissue sliowing a 

 zone of cellular infiltration. 



Microscopically, the principal change exhibited by necrosing tissues 

 is the disappearance of the nuclei, shown especially by their partial or 

 complete loss of the staining quality with the ordinary nuclear staining 

 reagents (hsematoxylin, carmine stains). Sections of normal tis.sues 

 present their cells and nuclei stained with clear definition and distinct 

 color; necrotic portions look as though they were without nuclei, and 

 either refuse to take the stain or only assume a faint diffuse coloration. 

 The nuclear changes may consist of a loss of a definite outline, accuinu- 



