560 



THE DUCTLESS GLANDS ENDOCKIN GLANDS 



of the interfollicular stroma. Colloid material, similar to that within the 

 follicles, has been repeatedly found within the lymphatic vessels (Baber, 

 Langendorf, Hiirthle) and may be readily demonstrated in most sections 



of the thyroid. Un- 

 doubtedly this does 

 not, however, repre- 

 sent the entire 'inter- 

 nal secretion' of the 

 gland. 



Blood Supply. 

 The arteries form a 

 rich plexus in and 

 about the capsule of 

 the thyroid, from 

 >rt/) y which numerous 

 branches penetrate the 

 organ, lying in the 

 connective tissue trab- 

 eculas between the lo- 

 bules; they are dis- 

 tributed to all parts 

 of the gland. They 

 supply a rich capillary 

 plexus in the walls of 

 the follicles. The 

 veins retrace the 

 course of the arteries. 

 The walls of the 

 smaller venules consist 

 only of endothelium, 

 with a very thin coat 

 of fibre-elastic connec- 

 tive tissue. 



Ly mphatics . Th e 



FIG. 484. DIAGRAM OF PHARYNX OF HUMAN EMBRYO, 

 SHOWING THE ORIGINS OF THE ANLAGES OF THE 

 THYMUS, THYROID AND PARATHYROIDS (EPITHELIAL 

 BODIES). 



Thy 1 , earliest position of thyroid anlage; Thy 2 , sec- 

 ondary position of thyroid anlage; Tgd, thyroglossal 

 duct; Fc, foramen cecurn; LThy, lateral thyroid an- 

 lages; Pihy, parathyroid bodies; pb, postbranchial 

 body; T, tonsil; I, II, III, IV, V, pharyngeal pouches; 

 a, b, first and second branchial grooves ('gill clefts'); 

 1, 2, 3, first, second and third aortic arches in the 

 cores of the branchial arches. The complete wall of 

 the pharynx is only shown at the right, above. (Adapt- 

 ed from Kohn.) 



thyroid is very abun- 

 dantly supplied with lymphatic vessels. These form a plexus of 

 very broad lacunar capillaries in the interfollicular connective tissue, 

 where they stand in intimate relation with the follicular epithelium. 

 From this plexus vessels pass to the interlobular connective tissue, 'in 

 which they form a second plexus, whence lymphatic vessels pass out of 



