Vascular System of the Thyroid Gland. 477 



form of a delicate membrane which supports the epithelial cells. 

 The sections examined in the course of my own studies indicate 

 a division of the gland by septa into lobes and lobules, and as will be 

 shown in this paper, definite vascular units can be dissected out, 

 which correspond to these structural units. Streif (13), by use of 

 the Born wax model method, has shown that the glandular structure of 

 the thyroid consists of closed follicles which are separated from each 

 other by fine connective tissue. He also showed that a system of 

 canals is not present and that the follicles do not communicate with 

 each other. 



There seems to be no extensive literature upon the microscopic 

 blood-supply of the thyroid. Kohlrausch (17) in 1853 drew atten- 

 tion to the fact that the follicles are surrounded by a rich capillary net- 

 work. This fact, as well as the presence of many lymphatic spaces 

 surrounding the follicles, is mentioned in the textbooks of anatomy 

 and histology. Wolfler devotes some space to the consideration of the 

 blood-vessels. He studied them principally from the embryological 

 standpoint, in their relation to the developing gland. He observed 

 a network of capillaries surrounding each follicle and twigs from 

 the blood-vessels to the follicles, but does not seem to have studied 

 them further and no drawings illustrating these points are found 

 in his monograph. Streckeisen (18) has made a very careful study 

 of the gross distribution of the arteries supplying the thyroid gland. 

 Landstrom (19) studied the gross distribution of the arteries and paid 

 especial attention to the subject of the arterial anastomoses, 

 article gives a resume of the work done upon this subject with a com 

 plete bibliography. 



In my own studies the injection method was used practically 

 altogether. Specimens were injected with various injection masses — 

 India ink and carmine, ultramarine blue, vermillion (mercuric sul- 

 phide) granules in various per cent, gelatine solutions. In some cases 

 single injections were made either into the arteries or veins, in 

 other cases double injections were made, filling both arteries and 

 veins. India ink and carmine both give very good injections of the 

 follicular blood-supply, as the masses on account of the small size of 

 their granules easily penetrate the capillary bed. Some very good 



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