THE THYROID AND PARATHYROIDS 275 



sends septa into the interior of the organ, which septa convey 

 bloodvessels and nerves destined for the supply of the gland 

 substance. 



The protoplasm of the cells often appears to be homogeneous ; 

 it does not stain well with eosin, and is vacuolated. The 

 nuclei are spherical and about 4 /m in diameter, and frequently 

 show a chromatic network. Permeating the whole glandule, 

 and even separating the individual cells in many places, is a 

 delicate network of fine fibres, which appear to be of a distinct 

 nature from ordinary connective tissue. It is stained by 

 eosin and faintly also by orcein. Near the periphery of the 

 organ the cells are smaller and lack this special sheath. 



bid. v. 



FIG. 78. Normal parathyroid of dog. (X 120). 

 .9.c.c., solid columns of cells ; bid. v., bloodvessel. 



In man and different mammals, Kohn distinguishes three 

 different arrangements of the epithelium cells which may be 

 met with : (1) A compact cell mass ; (2) a retiform tissue ; 

 and (3) a lobular conformation. These different arrangements 

 are not characteristic of any species or any age, but may be 

 found side by side in the same glandule. 



In the cat the internal parathyroid has a peripheral layer 

 of cylindrical cells, and there appear to be other differences 

 in structure between this body and the external parathyroid. 

 Thus the cells 'are not so closely packed in the internal as in 

 the external gland, and their outlines are more easily distin- 

 guished. Further, the cell nuclei of the internal parathyroid 

 (Jo not stain so deeply as those of the external body. This 



