TUBERCLE. 141 



These cells are at first so sparingly produced that wide bridges 

 of protoplasm intervene between them ; this also may be seen in 

 fig. 43, 6. As they grow more plentiful, the bridges waste 

 away, the newly developed elements touch each other, and are 

 flattened to some extent by mutual contact. The quantitv of 

 residual protoplasm is very trifling. What there is goes to fill 

 that system of inter-communicating lacuna3 which is necessarily 

 left between a number of spherical structures when in apposition ; 

 it forms a delicate network in whose meshes the tubercle-cells 

 are embedded. Such a network is shown in fio^. 43, 4, the 



O 7 7 



cells having been partially removed by pencilling. It consists of 

 fine round threads, which widen out here and there to form small 

 three-cornered expansions. This always denotes that the con- 

 tact between two adjoining cells has been imperfect, so that a 

 wider film of protoplasm has been left between them. Even 

 nuclei may still be met with in some of the nodal points of the 

 reticulum. The entire structure therefore is in some respects 

 like the finer trabecular networks in the interior of lym2Dhatic 

 glands ; and on this ground alone I was formerly led to institute 

 a comparison between the tissue of tubercle and that of the 

 lymphatic glands ; and, in common with other anatomists 

 ( Virchoiv), to regard tubercle as being actually a lymphoid or 

 lymphomatous morbid growth. What mainly confirmed me in 

 this view however was the similarity between tubercle and 

 the formation of perivascular lymphatic sheaths; the latter 

 process being, in my opinion, the fundamental element in the 

 production of the substance of the ly m2:»hatic glands. Mean- 

 while, however, it was found that the growth of miliary tubercles 

 was inseparably connected, not indeed with the presence of a 

 blood-vessel as such, but only with that of an endothelium. 

 Specific irritation of the endothelia of the lymphatics, the serous 

 membranes, and the blood-vessels (ScJiiippel) is the essential 

 factor in the production of the miliary nodule ; and it is only 

 because the lymphatics run by preference in the immediate 

 neighbourhood, in the adventitia of the blood-vessels, that 

 miliary tubercles also exhibit a preference for that locality. (For 

 the development of tul)ercles on the serous membranes and in 

 the lungs, see special chapters on the morbid anatomy of those 

 organs.) 



