HISTOLOGY OF TUBERCULAR NODULES. 217 



of its wall may proliferate, and thus a ring of nuclei be 

 formed round a small central thrombus. Such an occurrence 

 gives rise to an appearance closely resembling a typical 

 giant cell. 



Giant cells are found especially when the caseous change 

 is relatively not very active that is, in circumstances where 

 the formative processes have time to come into play. If 

 the centre of the nodule becomes caseous, giant cells may 

 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 very acute tuberculosis, also, the com- 

 mencement 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 the 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 



