206 PRACTICAL HISTOLOGY [XXVI 



In the dog the cell-cylinders of the outer zone of the cortex 

 join in curves at the surface ; the cells are flattened with their 

 long axis across the axis of the cylinder. 



In the supra-renal gland of birds, hardened in chromic 

 acid '2 p.c. and cut frozen, the cells between the anastomosing 

 epithelial cords are stained brown somewhat like those of the 

 medulla of the mammal ; the cells of the epithelial cords may 

 contain fat globules. 



Thymus. 



The corpuscles of Hassall are fairly numerous in the thymus 

 of man and cat, fewer in the rabbit and guinea-pig, and still 

 fewer in the rat. In the adult, the thymus is chiefly formed of 

 fibrous connective tissue and fat. 



A small piece of thymus tissue is present in the thyroid of 

 the cat, generally close to the parathyroid. 



