130 NORMAL HISTOLOGY AND ORGANOGRAPHY. 



invaded by connective tissue and fat, so that at the 

 age of puberty only a remnant of the original struc- 

 ture remains. 



In the child the thymus is a paired, elongated, 

 lobulated, ductless organ that lies partly in the neck 

 and partly in the thorax upon the large blood- 

 vessels. Structurally we recognize a capsule with 

 trabecul<z, pulp and the corpuscles of Hassal. 



1. Capsule and Trabeculcz. The capsule consists 

 of dense connective tissue, mostly nonelastic fibers 

 and cells. Processes or trabeculce pass into the or- 

 gan from the capsule and divide it up into distinct 

 angular lobules. Fibers from the trabeculae enter 

 the lobules where they interlace to form a supporting 

 reticulum. 



2. Pulp. This consists of lymphoid cells that fill 

 the intersticies of each lobule. The cells are more 

 densely packed along the periphery of each lobule, 

 so that an outer or cortical layer can be distin- 

 guished from a central portion, the medulla. 



3. Corpuscles of Hassal. 

 These are nests of epithelial 

 cells that lie in the medulla 



Ep ce!lf. ial and are remnants that show 

 the epithelial origin of the or- 



Fig. 94. Corpuscle of ^~ - . , 



Hassal surrounded by lym- gan. They stain red with eo- 



phoid cells from the me- sin an( J are f oun d in no Other 



organ. It is affirmed that 



these epithelial cells continue to grow after birth and 

 may be found late in life when only remnants of the 

 thymus is present. 



