l68 RELATIONS OF BACTERIA TO DISEASE. 



diseases often known as the infective granuloniata, of which 

 tubercle, leprosy, glanders, actinomycosis, syphilis, etc., are 

 examples. A hard and fast line, however, cannot be drawn 

 between such conditions and those described above as acute. 

 In glanders, for example, especially in man, the lesion produced 

 by the glanders bacillus often approaches very nearly to an 

 acute suppurative change, and sometimes actually is of this 

 nature. Whilst in these diseases the fundamental change is 

 the same, viz., a reaction to an irritant of minor intensity, the 

 exact structural characters and arrangement vary in different 

 diseases. In some cases the disease may be identified by the 

 histological changes alone, but on the other hand this is often 

 impossible. These changes often include the occurrence of 

 degenerations or of actual necrosis in the newly formed tissue. 

 In the granulomata, infection of other parts from the primary 

 lesion takes place chiefly by the blood-vessels and lymphatics, 

 though sometimes along natural tubes such as the bronchi, 

 intestine, etc. The organs specially liable to be the site of 

 secondary lesions vary in different diseases, as already ex- 

 plained. 



(2) General Lesiojis produced by Toxins. — In the various 

 infective conditions produced by bacteria, changes commonly 

 occur in certain organs unassociated with the presence of the 

 bacteria ; these are produced by the action of bacterial products 

 circulating in the blood. Many such lesions can be produced 

 experimentally. The secreting cells of various organs, especially 

 the kidney and liver, are specially liable to change of this kind. 

 Cloudy swelling, which may be followed by fatty change or by 

 actual necrosis with granular disintegration, is common. Hya- 

 line change in the walls of arterioles may occur, and in certain 

 chronic conditions waxy change is brought about in a similar 

 manner. The latter has been produced in animals by the 

 repeated injection of the staphylococcus aureus. Capillary 

 haemorrhages are not uncommon, and are in many cases due to 

 an increased permeability of the vessel walls, aided by changes 

 in the blood plasma, as evidenced sometimes by diminished 

 coagulability. Similar haemorrhages may follow the injection of 

 some bacterial toxins, e.g. of diphtheria, and also of vegetable 

 poisons, e.g. ricin and abrin. Skin eruptions occurring in the 

 exanthemata are probably produced in the same way, though 



