THE DUCTLESS GLANDS. 193 



sinuses, corresponding to those in the lymphatic nodes, are present 

 in the thymus (Fig. 169). 



The function of the thymus is still a matter of doubt. It has 

 been regarded as one of the sites in which red blood-corpuscles are 

 formed, and also as a temporary lymphadenoid organ playing the 

 part of the lymph-nodes until these have become fully developed in 

 other parts of the body. 



The thymus is connected with the thyroid by a strand of thymus- 

 tissue, and isolated thymus-lobules are found embedded in the 

 edges of the thyroid, near the parathyroid body (see Fig. 159). 



The bloodvessels ramify in the septa of the organ and send 

 branches into the lymphoid follicles. The lymphatic vessels accom- 

 pany the bloodvessels and surround the lobules, but do not appear 



FIG. 170. 



I 



/ ''<* 



: ^ V ~ V;, V 



: 



-<*- ^ OF 



^ ? 



<e -s. 



Section of the carotid gland and carotid arteries near their origin. (Marchand.) ci, internal 

 carotid ; ce, external carotid ; glc, carotid gland ; I, I, groups of epithelial cells ; i, fibrous 

 tissue between the epithelial groups ; g, bloodvessel. Numerous vessels are also seen 

 within the gland. 



to penetrate into the lymphadenoid tissue. The nerves are small 

 and not numerous. They accompany the bloodvessels, but nervous 

 terminations have not been traced as distributed to the lymphade- 

 noid tissue. 



The involution of the gland appears to be accomplished through 



13 



