170 



THYMUS 



is an absence of agreement among those who have worked at this difficult subject 

 as to the presence of this accessory element in man. 



parathyroid III. 



thymus 



mes. thyroid 



parathyroid IV. 



I at. thyroid 



pharynx 



-parathyroid III. 



t hymns 



parathyroid IV. 

 lat. thyroid 



FIG. 213. KECONSTBUCTION OF BRANCHIAL DERIVATIVES IN A HUMAN EMBRYO OF 14 MM. 

 (After Tourneux and Verdun.) 



c.a. j.v. 



parathyroid IV 

 lat. 



raid IV. 1F~*\ fe 

 . thyroid ~~W 



V 



mes. thyroid % 

 parathyroid III. 



lat. thyroid 

 parathyroid IV. 

 ~" mes. thyroid 

 -I parathyroid III. 



thymus ves. 

 thymus 



u 



thymus ves. 

 thymus 



FIG. 214. KECONSTRUCTION OF THE BRANCHIAL DERIVATIVES IN A HUMAN EMBRYO OF 16 MM. 

 (After Tourneux and Verdun.) 



c.a., carotid artery; j.v., jugular vein; thymus ves., vesicle of thymus. 



pyr. c.a. .;'.*> 



j.v. c.a 



par. IV 

 par. III. 



v.c.d. 



FIG. 215. KECONSTRUCTION OF THE THYROID AND THYMUS GLANDS WITH THE VEINS AND ARTERIES. 

 A, IN A HUMAN EMBRYO OF 26 MM. ; AND B, IN ONE OF 24 MM. (After Tourneux and Verdun.) 



In A the thymus lie in front, in B behind the left innominate vein. 



thyr., thyroid; thym., thymus; par. IV., parathyroid of fourth pouch; par. III., parathyroid 

 of third pouch; pyr., pyramidal lobe of thyroid; thyg., thyroglossal duct; c.a., carotid artery; 

 j.v., jugular vein ; v.c.d., vena cava dextra ; v.c.s., vena cava sinistra ; v.sc.d., vena subclavicularis 

 dextra ; v.sc.s., vena subclavicularis sinistra. 





