388 



USES OF THE LIVER DUCTLESS GLANDS 



The lobules 'are composed of rounded vesicles, ten to fifteen in number 

 and T J^ to Q of an inch (200 to 600 /i) in diameter. The walls of these 

 vesicles are thin, finely granular and fragile. The vesicles contain a 

 small quantity of an albuminous liquid, with cells and free nuclei. The 

 cells are small and transparent, and the nuclei are spherical, relatively 

 large, containing one to three nucleoli. The free nuclei are rounded 

 A B G 



Fig- 79- Thyroid and thymus glands (Sappey). 



A. i, right lobe of the thymus ; 2, left lobe ; 3, groove between the two lobes ; 4, lungs, the anterior 

 borders raised to show the thymus ; 5, terminal branch of the internal mammary vein ; 6, thyroid gland ; 

 7, median inferior thyroid veins; 8, lateral inferior thyroid veins; 9, common carotid artery; 10, in- 

 ternal jugular vein; n, pneumogastric nerve. B, right lobe of the thymus with the investing mem- 

 brane removed: i, upper extremity of the lobe; 2, lower extremity; 3, external border; 4, internal 

 border. C, arrangement of the lobules of the same lobe, around the central cord : I, upper extremity 

 of the lobe ; 2, lower extremity ; 3, 3, 3, lobules ; 4, 4, central cord. 



and contain several distinct nucleoli. Histologists describe a cortex 

 and a medullary portion. In the latter are small masses of imbricated 

 epithelium, known as the concentric corpuscles of Hassall (see Plate 

 IX, Fig. 5). 



The bloodvessels of the thymus are abundant, but their calibre is 

 small and the gland is not very vascular. They are derived chiefly 



