1878.] 



of the Thyroid Gland. 



57 



animals. In the tortoise a network of lymphatics can be injected, of 

 which the smaller ramifications run between almost all individual 

 vesicles. The homogeneous or granular material which I have de- 

 scribed in the lymphatics of the dog's thyroid, has been observed in 

 the same vessels in other thyroid glands, e.g., in those of horse, man, 

 sheep. It occurs in both injected and uninjected glands. The quan- 

 tity varies much in different glands of the same animal, it being 

 sometimes present in large quantities, and at other times appearing to 

 be entirely absent. These observations so far merely confirm the results 

 arrived at in the dog. In the thyroid gland of birds, however, a 

 different arrangement of parts takes place. On injecting the thyroid 

 gland of a pigeon by the method of puncture with Berlin blue, it be- 

 comes swollen, and the injection is seen running in the jugular vein, 

 with which the gland is in close apposition.* Examination of sections 

 of the gland shows that the injection has entered vessels containing 

 blood-corpuscles. The same vessels become filled on injecting in like 

 manner with nitrate-of-silver solution. To ascertain whether by the 

 puncture method the blood-vessels really become injected, another 

 gland was injected with Berlin blue from the lower part of the carotid 

 artery, the artery at the same time being secured above the gland. In 

 this case, in which the injection had entered the capillaries and veins, 

 it was evident that these were the same system of vessels which were 

 injected by the method of puncture. I may, therefore, state that on 

 repeated injections of the thyroid gland of the pigeon, both with Berlin 

 blue solution and with nitrate of silver by the method of puncture, I have 

 been unable to inject any system of lymphatic vessels, but have ahu ays found 

 the injection in the blood-vessels of the gland. In. the thyroid gland of 

 this bird the blood-vessels present the following characters : — The 

 capillaries, as usual, form a network running between the individual 

 gland- vesicles, but in proportion to the size of the vesicles (which in 

 this gland are as a rule small), they do not appear so minute, nor to 

 have such complicated ramifications as in the case of mammalia, but 

 resemble more the distribution of the lymphatics in some of those 

 animals. The veins frequently surround, either partially or entirely, 

 the arteries which they accompany. Immediately under the capsule of 

 the gland numerous large veins are seen, and in the fibrous capsule 

 itself, I have noticed layers of blood-corpuscles, which appear to be 

 contained in blood-vessels communicating with the veins of the interior. 

 Once or twice I have noticed in the large veins on the surface of the 

 gland (under the capsule), in addition to blood-corpuscles, and perhaps 

 coloured injection, a greater or less quantity of a material of homo- 

 geneous aspect, presenting an appearance similar to the material seen 



* It will be remembered that on injecting the dog's thyroid gland in a similar 

 manner, the injection was seen emerging from the gland in lymphatic vessels which 

 ran to neighbouring lymphatic glands. 



