204 PRACTICAL HISTOLOGY [XXVI 



The cells of the cortex, especially those of the outer part of the 

 cell-columns, contain usually a number of small fat globules ; in 

 the section they may have been dissolved ; if so the cells under 

 a high power will appear to have a very distinct network. 



6. Tease out a piece of fresh supra-renal (a) from the cortex, 

 (6) from the medulla. Note that the cells of the cortex are 

 granular or contain fat globules, those of the medulla are trans- 

 parent ; irrigate with potassium bichromate 1 to 2 p. c., the cortex 

 cells become yellow, the medulla cells become reddish- brown. 



7. Section of a lobule of the thymus of a new- 

 born animal (cat). (Mercuric chloride; picrocarmine.) 



a. Note under a low power 



The connective tissue sending in trabeculae and 

 dividing the cortex into alveoli. The alveoli are 

 crowded with leucocytes. 



The central mass or medulla of the lobule staining 

 less than the cortex. 'In it are some small bodies 

 concentrically striated, the corpuscles of Hassall. 



6. Note under a high power 



In the alveoli of the cortex there is no indication of 

 a lymph channel (cp. p. 146). 



In the medulla, small leucocytes are relatively less 

 frequent than in the cortex ; connective tissue cells 

 with membranous processes and giant-cells may be 

 seen ; the striation of the corpuscles of Hassall is due 

 to layers of flattened cells. 



DEMONSTRATION. 



Section of thymus with blood vessels injected. 

 Note that in the cortex the capillaries run, broadly 

 speaking, in loops between the periphery and the 

 centre of the alveoli. (Cp. with lymphatic gland, 

 p. 147.) 



