18 



The Endocrine Organs 



which mainly take the form of sinus-like capillaries. There is a capsule of 

 areolar tissue sending in processes to join the interstitial tissue of the organ : 



v; : . 



Fig. 10. — Section of parathyroid and adjacent thyroid tissue (rat). Magnified 50 diameters. 

 The vesicles of the thyroid are filled with colloid. The parathyroid is of the reticular 

 type, consisting of loosely arranged trabeculse. 



^ 



Fig. 11. — The same, from another preparation. The thyroid vesicles are 

 empty and their cells columnar. 



plain muscle cells have been described in this ; it may also contain fat-cells.. 

 Besides the ordinary or principal cells of the gland — which are small and 



