Vascular System of the Thyroid Gland. 479 



face anastomoses were easily demonstrated. Landstroni also expresses 

 the conviction that anastomoses also occur within the gland, but did 

 not succeeded in demonstrating them. The method that Landstroni 

 employed was that of injecting the arteries with Woods' metal, and 

 then taking a Roentgen-ray picture of the gland. In my own 

 studies several glands were injected with celloidin, and then by di- 

 gesting with artificial gastric juice, corrosion specimens were ob- 

 tained in which the arterial tree could be followed from its trunk to 

 its termination in the individual follicles. In no case was it pos- 

 sible to find definite arterial anastomoses beneath the surface of the 

 gland. The arterial tree is so exceedingly complex that it is difficult 

 to decide this point absolutely. It is also easy to imagine what a com- 

 plex lucture would be obtained by Landstrom's method. In many 

 eases when from study under the microscope a definite anastomosis 

 appeared to exist, yet after carefully moving the blood-vessels with 

 a pair of fine needles it was seen that tlie two arteries did not really 

 anastomose, but ran out each to its termination, entirely independent 

 of the other. In many cases, large branches of the thyroid arteries 

 would turn and twist about in great confusion, without, however, 

 anastomosing. In the cat's thyroid, anastomoses occur as are seen in 

 Fig. 1. Gelatin injections of the dog's thyroid, show a few anasto- 

 moses, but they occur between branches of the same artery, and not 

 between branches of the superior and inferior thyroid arteries. At 

 any rate, if anastomoses are present in my specimens of human 

 thyroids they are of small size. 



The capsule of the thyroid gland, like similar tissues, has a very 

 scant blood sup})ly. The arteries upon entering the gland give off 

 small branches at various places which join each other to form a net- 

 work throughout the substance of the capsule dividing it into large 

 diamond-shaped areas. Each artery is accompanied, as a rule, by two 

 veins, which are connected at various places by bar-like veins which 

 rnn across the artery. The veins anastomose in the same manner as 

 the arteries, and empty at various places into the large veins that are 

 emerging from the interior of the gland. Occasionally a capsule 

 vein empties into a vein within the gland, but such anatomoses 

 are infrequent. The same general scheme of this circulation is ob- 



