590 



SPECIAL HISTOLOGY. 



elements of the true glands, approach nearest to them in size, but solid 

 bodies, which, towards the cavity of the lobules or its accessory cavities, 

 are intimately coherent, whilst on the outer side they are separated 



Fi-. 242 



243. 





^^^Mim^- 







from each other. Each lobule may also be regarded as a thick-M^alled 

 vesicle, with protrusions, whose inner surface is even and continuous, 

 whilst the outer is subdivided into the above-mentioned gland-granules, 

 by more or less deep fissures. 



In many cases, a condition different from that just described is met 

 with, inasmuch as, instead of a contracted canal, into which the cavities 

 of the gland-lobules open, each thymus contains a larger though con- 

 tracted cavity, i-1 inch wide, with which the gland-lobules communi- 

 cate by larger fissure-like openings. Many anatomists, and among the 

 more modern, particularly Sir A. Cooper, consider the existence of this 

 cavity as normal ; whilst others, at the head of whom is Simon, are dis- 

 posed to regard it as produced by the methods of investigation employed 



Fig. 242. — Portion of the thymus of a Calf, unfolded : a, main canal ; b, glandular lobules ; 

 c, isolated gland-granules, seated upon tlie main canal. Natural size. 



Fig. 243. — Half of the human thymus, with a large cavity in the inferior wide portion 

 and numerous orifices leading into the lobules. 



