NO. l6 DUCTLESS GLANDS OF THE ALLIGATOR REESE 7 



granular. The close arrangement of the nuclei would indicate that 

 the cells are small. 



Throughout the trabeculae numerous groups of red blood corpus- 

 cles are seen ; usually, but not always, the endothelium of the capil- 

 laries in which they are contained may be seen. The trabeculae and 

 capsule are made up of a fairly dense mass of fibres (ct) among 

 which are scattered small, oval nuclei. The structure which has been 

 called the post-branchial body (pb) consists of a mass of cells whose 

 nuclei do not, perhaps, stain so deeply as those of the nearby para- 

 thyroid cells and are not so closely set. As in the parathyroid no cell 

 walls can be determined, but the cells are probably somewhat larger 

 than in the former organ. 



Numerous blood capillaries (fa) are to be seen and also certain 

 bodies (he) that resemble Hassall's corpuscles. The distinctness of 

 these bodies is exaggerated in the figure. No vesicles, with or without 

 colloid, are to be seen in this section. 



THYMUS GLAND 



The thymus gland is a very inconspicuous organ in the alligator. 

 It is very long and narrow and may easily be overlooked in dissecting 

 a small animal. In an alligator of 85 cm. length it is about 75 mm. 

 long and about 2 to 3 mm. wide, except at its extreme posterior end 

 where it may be somewhat enlarged. It lies against the muscles of 

 the neck, lateral and dorsal to the esophagus, with its enlarged pos- 

 terior end near the main blood vessels of the heart. It is so closely 

 associated with certain blood vessels of the neck that the latter may 

 be easily removed with the gland in dissection. It has the same 

 general color as the surrounding tissues, which adds to its incon- 

 spicuousness. 



A part of a transverse section of the gland as seen under a rather 

 low magnification is shown in plate 2, figure 10. The gland is sur- 

 rounded by a rather thick mass of connective tissue (c) almost too 

 diffuse to be called a capsule, which sends in numerous broad trabec- 

 ulae (/) that divide the gland into the characteristic lobules. 

 Numerous blood vessels (bv) are seen in the capsule and in the 

 trabeculae. 



The gland tissue proper shows but little difference between the 

 outer, cortical region (Cor) and the central or medullary region, such 

 as is seen in the higher vertebrates. In both regions, if any distinction 

 between them be made, numerous corpuscles of Hassall (he) may be 



