GENERAL PATHOLOGY. 21 



Such inflammations are 

 termed gangrenous or necrotic. 



Dij)htlierltic is a special variety of necrotic inflammation. 

 It afi'ects the surfaces of mucous membranes and wounds. 



In this form the mucous membrane is covered by a 

 false membrane, composed of a network of fibrin, con- 

 taining here and there leucocytes in the meshes. 



The epithelium is quite destroyed, with more or less of 

 the subjacent tissue. This form of inflammation charac- 

 terizes the disease called ' diphtheria/ but a similar patho- 

 logical change may occur on any mucous membrane, e.g., 

 that of the intestine (dysentery). 



3. New Growths. — Inflammations ending in new growths 

 are the so-called productive inflammations already con- 

 sidered. 



ETIOLOaY OF INFLAMMATION. 



Etiologically, inflammations are divided into simple or 

 traumatic, and cryptogenetic. 



1. Simple or Traumatic Inflammations. — Are due to 

 some injurious agency, such as mechanical violence, action 

 of chemicals, excess of heat or cold, or to prolonged local 

 anaemia. Inflammation from these causes has no tendency to 

 spread beyond the part originally injured, or to pass on to 

 more advanced stages, after the causes have ceased to act. 

 Under this heading come inflammations due to wet or 

 cold, * rheumatic' and 'reflex' influences. 



Excessive functional activity is said by some to be a 

 direct cause of inflammation. 



Nervous influence is also regarded as a direct cause. 



2. Cryptogenetic Inflammations. — In very many of the 

 inflammations there has been no obvious chemical or 

 mechanical injury. Many of these have been shown to be 

 due to the action of various vegetable fungi, and evidence 



