HISTOLOGY 



lOI 



positions as well as the number of lobes is variable. Usually they are sit- 

 uated at the caudal end of each of the two lateral lobes of the thyroid. The 

 gland consists of densely arranged groups or cords of polygonal cells. In 

 some of these cells the nuclei are round and contain fine chromatin granules; 



Thyroid fDllicle 

 with colloid 



Parathyroid 



.^_ -.-»,»_ Blood vessel 



Fig. 42. — Thyroid and parathyroid glands. (X200.) 



in others the nuclei are elongated and contain a single large nucleolus. 

 According to Larionow (67), in young mice the former predominate, and in 

 old mice the latter, while mice of middle age occupy an intermediate posi- 

 tion. The supporting framework consists of reticular fibers and a network 

 of capillaries. 



The adrenal glands. — The adrenal glands are situated immediately 

 anterior to the kidneys. Each gland has a thin connective tissue capsule 

 which projects into the parenchyma and forms supporting trabeculae. A 

 cross section shows a central medulla and a peripheral cortex. Dependent 



