274 TUBERCULOSIS 



cell often shows signs of degeneration, such as hyaline change 

 and vacuolation, or it may be more granular than the rest of 

 the cell. The exact mode of formation of a tubercle follicle 

 varies, however, in different tissues. 



Though there has been a considerable amount of discussion as to the 

 mode of origin of the giant-cells, we think there can be little doubt that 

 in most cases they result from enlargement of single epithelioid cells, the 

 nucleus of which undergoes proliferation without the protoplasm dividing. 

 ■ These epithelioid cells may sometimes be the lining cells of capillaries. 

 Some consider that the giant-cells result from a fusion of the epithelioid 

 cells ; but, though there are occasionally appearances which indicate such 

 a mode of formation, it cannot be regarded as of common occurrence. In 

 some cases of acute tuberculosis, when the bacilli become lodged in a 

 capillary, the endothelial cells of its wall may proliferate, and thus a riDg 

 of nuclei may be seen round a small central thrombus. Such an occur- 

 rence gives rise to an appearance closely resembling a typical giant-cell. 

 There can be no doubt that the cell necrosis and subsequent caseation 

 depend upon the products of the bacilli, and are not due to the fact that 

 the tubercle nodule is non-vascular. This non-vascularity itself is to be 

 explained by the circumstance that young capillaries cannot grow into a 

 part where tubercle bacilli are active, and that the already existing 

 capillaries become thrombosed, owing to the action of the bacillary 

 products on 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 distribution 

 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 amyloid change in the organs 

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

 especially pyogenic, organisms, secondarily present in the 

 tubercular lesions. This matter, however, requires further 

 elucidation. 



Presence and Distribution of the 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. 

 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 



