USES OF THE LIVER DUCTLESS GLANDS. 



and very fragile. The vesicles contain a small quantity of an albuminoid 

 fluid, with cells and free nuclei. The cells are small and transparent, and 



FIG. 141. Thyroid and thymus glands (Sappey). 



A. 1, right lobe of the thymus ; 2, left lobe ; 3, groove between the two lobes ; 4, lungs, the anterior bor- 

 ders 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, internal jugular vein ; 11, pneumogastric nerve. 



B. Right lobe of the thymus with the investing membrane removed. 1, 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. 1, upper extremity of the 



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



the nuclei are spherical, relatively large, and contain one to three nucleoli. 

 The free nuclei are also rounded and contain several distinct nucleoli. These 

 vesicles are easily ruptured, when their contents exude in the form of an 

 opalescent fluid, which is sometimes called the thymic juice. 



Anatomists are somewhat divided in their opinions with regard to the 

 structure of the central cord and the lobules. Some adopt the view advanced 

 by Astley Cooper, that the cord has a central canal connected with cavities 

 in the lobules ; while others believe that the cavities thus described are pro- 

 duced artificially by the processes employed in anatomical investigation. 

 The latter opinion is probably correct. 



The blood-vessels of the thymus are abundant, but their caliber is small 

 and the gland is not very vascular. They are derived chiefly from the in- 

 ternal mammary artery, a few coming from the inferior thyroid, with occa- 



