236 TUBERCULOSIS. 



be formed later in the cellular tissue at the periphery. 

 According to the view here stated, both the epithelioid 

 and the giant cells are of connective tissue origin ; and 

 we can see no sufficient evidence for the view held by 

 some observers, chiefly of the French school, that they 

 are formed from leucocytes which have emigrated from the 

 capillaries. 



Such are the usual changes which occur on the intro- 

 duction of the bacilli into connective tissue ; but the 

 tubercle nodule has not always the same mode of formation 

 and structure. In very acute tuberculosis of the spleen, 

 for example, a group of. bacilli may often be seen to have 

 caused cellular necrosis around them before any tissue 

 proliferation has taken place, and it may be only at the 

 margin of the larger and older follicles that epithelioid cells 

 are well seen. In acute cases, also, the commencement of 

 the tubercle nodule may sometimes be traced to a clump 

 of leucocytes surrounding bacilli in a capillary ; such an 

 appearance may sometimes be met with in the liver. The 

 great varieties in the appearance of tubercular lesions depend 

 upon the number of the bacilli and their manner of spread, 

 and accordingly on the proportion in which the proliferative 

 and degenerative changes occur. We thus find that cellular 

 proliferation is especially marked when the bacilli are few 

 in number. 



There can be no doubt, we think, from a careful study 

 of the tubercular lesions, that the cell necrosis and ulti- 

 mate 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, perspira- 



