134 RELATIONS OF BACTERIA TO DISEASE. 



be drawn between such conditions and those described 

 above as acute. In glanders, for example, the lesion 

 produced by the glanders bacillus often approaches very 

 nearly to an acute suppurative change, and sometimes actu- 

 ally is of this nature. In all these diseases the fundamental 

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

 intensity. The exact structural characters and arrange- 

 ment, however, vary in different diseases, so that in some 

 cases the disease may be identified by the histological 

 changes alone, without a bacterial examination, but on the 

 other hand, this is often impossible. In tubercle, for 

 example, in addition to the proliferative change, a cellular 

 necrosis is produced by the bacilli, leading ultimately to 

 caseation, whereas the latter does not occur in leprosy, 

 though a certain amount of degeneration and vacuolation 

 of cells may be found. In tubercle, giant-cells of some- 

 what 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 granulation 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, intestine, 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 commonly 

 occur in certain organs unassociated with the presence of the 

 bacteria, and these are no doubt produced by the action on 

 the tissues 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 often seen. 

 Hyaline change in the walls of arterioles may occur, and in 

 certain chronic conditions waxy change is probably brought 



