246 TUBERCULOSIS. 



their walls, and ultimately disappear. At the periphery of 

 tubercular lesions there may be considerable vascularity and 

 new formation of capillaries. 



The general symptoms of tuberculosis pyrexia, perspiration, 

 wasting, etc., are to be ascribed to the absorption and distribu- 

 tion throughout the system of the toxic products of the bacilli ; 

 in the case of phthisical cavities and like conditions where other 

 bacteria are present, the toxins of the latter also play an im- 

 portant part. The occurrence of waxy change in the organs is 

 believed by some to be chiefly due to the products of other, 

 especially pyogenic, organisms, secondarily present in the tuber- 

 cular lesions. This matter, however, requires further elucidation. 



Presence and Distribution of tJie Bacilli. A few facts may 

 be stated regarding the presence of bacilli, and the numbers in 

 which they are likely to be found in tubercular lesions. On the 

 one hand, they may be very few in number and difficult to find, 

 and on the other hand, they may be present in very large num- 

 bers, sometimes forming masses which are easily visible under 

 the low power of the microscope. 



They are usually very few in number in chronic lesions, 

 whether these are tubercle nodules with much connective tissue 

 formation or old caseous collections. In caseous material one 

 can sometimes see a few bacilli faintly stained, along with very 

 minute unequally stained granular points, some of which may 

 possibly be spores of the bacilli. Whether they are spores or 

 not, the important fact has been established that tubercular 

 material in which no bacilli can be found microscopically, may 

 be proved, on experimental inoculation into animals, to be still 

 virulent. In such cases the bacilli may be present in numbers 

 so small as to escape observation, or it may be that their spores 

 only are present. In subacute lesions, with well-formed tubercle 

 follicles and little caseation, the bacilli are generally scanty. 

 They are most numerous in acute lesions, especially where 

 caseation is rapidly spreading, for example, in such conditions 

 as caseous catarrhal pneumonia (Fig. 90), acute tuberculosis of 

 the spleen in children, which is often attended with a good deal 

 of rapid caseous change, etc. In acute miliary tuberculosis a 

 few bacilli can generally be found in the centre of the follicles ; 

 but here they are often much more scanty than one would ex- 

 pect The tubercle bacillus is one which not only has compara- 



