THE THYMUS GLAND. 



321 



Fia:. 2IO 



D.m. 



b. Minute structure (Fig-. 211). 



[The gland is surrounded by a connective capsule, which is 

 indented on the inner surface to form 

 a hilus through which blood-vessels 

 course into the organ. 



The capsule sends in numerous fine 

 trabeculae, which form a connective- 

 tissue skeleton such as is found in all 

 lymphatic glands. The corpuscles of 

 the trabeculae possess elongated nuclei 

 from 0'0I9 to 0*028 mm. in length, 

 and o-oio to 0-015 ^^^- in breadth 

 (Tolldt). The trabeculae support a 

 network of blood-vessels. 



The meshes of this sustentacular 

 tissue are filled with cells ; these are : 



(a) Lymphoid cells, rounded or oval, possessing a round nucleus 

 and nucleolus, and an extremely small amount of adhering proto- 

 plasm; the size of the nucleus is from o'Oii to 0"0i5 mm. 

 (Tolldt). 



Fie:. 211. 



Dissection to show relations of the 

 tliymus gland. 



De. M. deltoideus. 



D.m. M. depressor uiandibulae. 



L.d. M. latissimus dorsi. 



St M. sternocleidomastoldeus. 



Tf Tympanic membrane. 



Th Thymus gland. 





,jr6 v®j) 





IT 



fr^ 



From various sections from tlie thymus gland of Rana esciilenta. — G. H. 



I. Complete gland (Hartnack, Oc. I, Syst. 3). 

 a Pigment-cells. 

 II. Portion of a section (Hartnack, Oc. I, Syst. 7) showing small coi-puscles of Haj^sall. 



III. Portion of a section showing lohules with degenerating cells. 



a Capsule of lobe. 



6 Lobules. 



c Large corpuscle of Hassall, surrounded by normal tissue. 



IV. Xerve-ceU? (corjiuscle of Hassall), after Fleischl. 



(^) Corpuscles of Hassall (Fig. 211 II, III, and IV) are, as a 

 rule, large bodies, but are subject to much variation in size. Their 



