482 



Ralph H. Major. 



much larger number of branches before penetrating the gland. This 

 is illustrated in Fig. 2. The superior thyroid divides into two main 

 branches which course down the sides of the gland, each giving off a 

 large number of branches, some of which are branches of the second 

 order, others of which give off branches of the second order. The 

 total number of the branches given off by the two main divisions of 

 the superior thyroid artery in the specimen drawn is forty-one. The 

 arteries of the second order are distributed as in the dog and pass 

 between lobes of the gland. 



The course of the arteries in the human thyroid resembles some- 

 what that of the dog, but presents differences which are apparent at 



RIT 



LIT 



Fig. 3. — Gross urtei-ial blood supply of bumau tbyroid. 



R S T — Right superior thyroid artery. R I T — Right inferior thyroid artery. 

 L S T — Left superior thyroid artery. L I T — Left inferior thyroid artery. 



first sight. The human thyroid gland differs from that of the dog 

 in shape, in the presence of a well-defined isthmus and in the fact 

 that in man the inferior thyroid artery is as large or larger than the 

 superior thyroid. Variations in the gross blood-supply of the human 

 thyroid are common, but a general scheme seems to be present, with 

 differences in method of anastomoses. Such a general scheme is 

 shown in Fig. 3. Here we see the superior thyroid artery approach- 



