GENERAL LESIONS. 151 



leading to caseation is produced by the bacilli, whereas in 

 leprosy the latter does not occur, though there may be a 

 certain amount of degeneration and vacuolation of cells. 

 In tubercle, giant-cells of somewhat characteristic appearance 

 are found ; in leprosy, large rounded cells often called 

 " lepra-cells " occur in large numbers ; in actinomycosis 

 bovis, there is an extensive growth of spindle-celled granula- 

 tion tissue which may form large masses, and so on. 

 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, intes- 

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

 secondary lesions vary in different diseases, as already 

 explained. 



(2) General Lesions produced by Toxines. In the various 

 infective conditions produced by bacteria, changes com- 

 monly 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. 

 Hyaline 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 

 toxines, e.g., of diphtheria, and also of vegetable poisons, 

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

 anthemata are probably produced in the same way, though in 

 many of these diseases the causal organism has not yet been 

 isolated. We have, however, the important fact that corre- 



