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E. V. COWDEY 



and nerves. The substance of the gland is divisible into cortical and 

 medullary portions. Small fragments of thyroid or parathyroid tissue 

 may be found within the thymus (as in the case illustrated in Fig. 2) ; 

 and conversely, masses of thymus IV in association with the thyroid 

 and parathyroids. 



Blood Supply. The thymus gland draws its blood supply, for the 

 most part, from the internal mammary arteries ; sometimes, in addition, 



Fig. 1. Thymus gland of full term fetus hardened by formalin injection in situ, 

 after Cunningham. 



from the inferior thyroid and pericardial arteries, but there is considerable 

 variation in this respect, A plexus is formed about the center of the 

 gland, from which branches radiate into the surrounding tissue. The 

 blood leaves the organ by numerous venules, which empty into the left 

 innominate vein and sometimes, also, into the internal mammary and 

 inferior thyroid veins. 



Lymphatics. Lymphatic plexuses enclose the lobules and accompany 

 the arteries. The details of their arrangement have been worked out by 

 Matsunaga. The lymphatic drainage from the thymus passes into the 



