260 H. E JORDAN 



veins follow the same course through the trabecula as the arteries. 

 Thus cross sections of the coarsest trabeculae show a pair of vascu- 

 lar comites. The artery has much the thicker wall, containing 

 a small amount of smooth muscle, and the smaller calibre. The 

 tips of some of the larger trabeculae contain capillary plexuses 

 which end in open spaces in the centre of follicular collections of 

 cells. The finer trabeculae and septa contain progressively more 

 delicate blood-vessels. In many cases a loop of capillaries forms 

 the centre of a follicle. Another conspicuous feature in connection 

 with the vascular trabeculae is the wide space which exists be- 

 tween them and the surrounding parenchyma. This is spanned 

 bj^ a delicate network of connective tissue fibers which color blue 

 in Mallory's stain, in contrast to the brown or black outlying 

 neuroglia fibers. The meshes are filled with a coagulum. These 

 spaces appear similarly pronounced in pineal bodies treated with 

 any of the above mentioned fixing fluids; also in those of the foetal 

 stages after half term. They can accordingly not be interpreted 

 as fixation artefacts, but are more probably lymph-spaces. 



The common cytologic characteristics of the several morpho- 

 logic types of parenchymal cells (oval, flattened, stellate, and 

 fusiform) are as follows: absence of cell membrane; vesicular 

 nucleus with a plasmosome, and many scattered chromatic gran- 

 ules; occasional presence of melanic granules; otherwise homoge- 

 neous or very finely reticular character of the cytoplasm. Atypi- 

 cally, some of the ' oval' cells may have short processes, these re- 

 sembling stellate cells lying in the meshes of the network formed 

 by the latter; or very rarely a cell (more usually a fusiform type) 

 may have a chromatic nucleus, a condition more probably indic- 

 ative of preparation for mitosis. In general the nuclei of neurog- 

 lia cells are darker than those of the inter-neuroglia cells — and 

 the more highly differentiate types of the former (i.e., with coarse 

 neuroglia fibers and flattened bodies) are frequently very chro- 

 matic (fig. 8). 



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