LOCAL LESIONS 183 



extent, that of diphtheria. In other cases it depends entirely 

 upon the point of entrance, e.g., malignant pustule and the con- 

 ditions known as wound infections. In others again, there is a 

 special tendency for certain parts to be affected, as the upper 

 parts of the lungs in tubercle. In some cases the site has a 

 mechanical explanation. 



When organisms gain an entrance to the blood from a primary 

 lesion, the organs specially liable to be affected vary greatly in 

 different diseases. Pyogenic cocci show a special tendency to 

 settle in the capillaries of the kidneys and produce miliary 

 abseesses, whilst these lesions rarely occur in the spleen. On 

 the other hand, the nodules in disseminated tubercle or glanders 

 are much more numerous in the spleen than in the kidneys, 

 which in the latter disease are usually free from them. The 

 distribution of the lesions thus cannot be explained on a 

 mechanical basis. Even in the case of the lesions produced by 

 dead tubercle bacilli, a certain selective character is observed. 



Acute Local Lesions. — The local inflammatory reaction presents 

 different characters in different conditions. It may be accom- 

 panied by abundant fibrinous exudation, or by great catarrh (in 

 the case of an epithelial surface), or by haemorrhage, or by 

 oedema ; it may be localised or spreading in character ; it may 

 be followed by suppuration, and may lead up to necrosis of 

 the tissues of the part, a good example of the latter event 

 being found in a boil. Examples will be given in subsequent 

 chapters. The necrotic or degenerative changes affecting 

 especially the more highly developed elements of tissues are 

 chiefly produced by the direct action of the bacterial poisons, 

 though aided by the disturbances of nutrition involved in the 

 vascular phenomena. It may here be pointed out that a well- 

 marked inflammatory reaction is often found in animals which 

 occupy a medium position in the scale of susceptibility, and that 

 an 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 ; there is less vascular disturbance 

 and a greater preponderance of the proliferative processes, lead- 

 ing to new formation of connective tissue. This formation 

 may occur in foci here and there, so that nodules 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. 



