LOCAL LESIONS. 133 



organisms, whilst fibrinous inflammation in serous cavities 

 is produced by a great many different bacteria. The last 

 statement also applies to numerous suppurative and catar- 

 rhal conditions. The inflammatory change in a Peyer's 

 patch in typhoid fever, though fibrinous exudation is less 

 marked, is followed by necrosis, while in the malignant 

 pustule of man, necrotic change attended by considerable 

 haemorrhage is one of the chief features. The great variety 

 in local reaction is well illustrated in the case of skin lesions 

 produced by bacteria. The necrotic or degenerative changes 

 affecting especially the more highly developed elements are 

 chiefly produced by the direct action of the bacterial poisons, 

 though aided by the disturbances of nutrition involved in 

 the vascular phenomena. 



In many of the acute inflammatory conditions, if not 

 attended by a fatal result, the disease comes to a natural 

 termination after a certain time, e.g., in pneumonia, ery- 

 sipelas, etc. These facts, the explanation of which is not 

 yet fully understood, have an important relation to the 

 subject of immunity, and will be discussed later. It may 

 also be pointed out that a well-marked inflammatory re- 

 action is often found in animals which occupy a medium 

 position in the scale of susceptibility, and that a given 

 organism which causes a general infection in a certain 

 animal may produce only a local inflammation when its 

 virulence is lessened. 



Chronic Local Lesions. In a considerable number of 

 diseases produced by bacteria the local tissue reaction is 

 a more chronic process than those described. In other 

 words, the specific irritant is less intense, so that there are 

 less acute inflammatory changes and a greater preponderance 

 of the proliferative processes, leading to new formation of 

 tissue. This formation may occur in foci here and there, so 

 that nodules of greater or less consistence result, or it may 

 be more diffuse. Such changes especially occur in the 

 diseases often known as the infective granulomata, of 

 which tubercle, leprosy, glanders, actinomycosis, syphilis, 

 etc., are examples. A hard and fast line, however, cannot 



