NUCLEI. 



117 



The membranous wall of the nuclei is certainly an albuminous 

 compound, and probably but little, if at all, different from the 

 younger cell-membranes. Generally the granules within it are mere 

 globules of fat, like those floating in the cell. 



Nuclei are found in all cells of embryos, and in adults also while 

 the cells are still young ; though in some cases, as in the fat-cell, 

 they subsequently disappear. 



Generally but a single nucleus exists in each cell ; but when a 

 cell is multiplying, as many nuclei arise as there are new cells to be 

 formed. 



In some cases, however, several nuclei naturally exist ; four, ten, 

 twenty, or even more, nuclei being found in the same cell. This is 

 especially the case with cancerous and other rapidly developed ma- 

 lignant growths. 



Free nuclei also take part in the formation of certain tissues as 

 in the rust-colored layer of the cerebellum, and in the granular 

 layer of the retina. 



Thus a nucleus is, histologically, an embryo cell. 



Pathological Developments of Nuclei. 



1. The characteristic structure of tubercle tubercle-corpuscles 

 consists of mere nuclei inclosing nucleoli, there being no cells in this 

 deposit. The other element of tubercle is an amorphous, semi-solid 

 hyaline substance, which, in the opaque or yellow variety, but not 

 in the gray or transparent tubercle, contains granules also (p. 108). 



The nuclear bodies of tubercle are usually oblong, polyhedral, 

 averaging -ggVi f an i ncn l n gj an d 454? f an ^ ncn wide. They 

 consist (1) of a delicate transparent membrane, with (2) a transpa- 

 rent, colorless, or faintly ambreous fluid, containing (3) granules, and 



Fig. 56. 



Fig. 57. 



Fig. 58. 



fl 0\J w : ia 



&$ 



*<e;% 



o 



--0 



W 





Fig. 56. Tubercle-corpuscles from peritoneum. Those at the right show the effects of acetic acid. 

 Fig. 57. Tubercle-corpuscles and granular homogeneous substance from lung. Fig. 58. Tubercle- 

 corpuscles from mesenteric gland. Free oil-globules are seen at the right in Fig. 57. 



