MR, E. C. BABER ON THE STRUCTURE OE THE THYROID GLAND. 
603 
pigment are sometimes seen, which, appear to be due to the absorption by the epithelial 
cells or reticulum of the colouring matter of the effused blood. Observations on the 
Dog lead to the inference that in this animal an escape of red blood-corpuscles is 
almost constantly taking place into a greater or less number of vesicles, and its occurrence 
in other animals also (Man, Tortoise, Conger Eel) renders it very probable that the 
passage of coloured blood-corpuscles into the vesicles is a normal occurrence in the 
thyroid gland. Further observations (Dog, Rook, Seal) also render it very probable 
that normally under certain circumstances an escape of red blood-corpuscles takes place 
into a large proportion of the vesicles of the thyroid gland. The blood thus effused 
contributes to a large extent to the formation of the “ colloid ” substance, and probably 
has an important bearing on the physiology and pathology of the organ. 
(c) Colourless bloocl-corpuscles are frequently found in the homogeneous material in 
the gland-vesicles of the Tortoise. A migration of colourless corpuscles into the vesicles 
is a normal occurrence in the Tortoise, but it may also take place in other animals. 
( d) Rounded masses, staining darkly with hematoxylin or of a bright yellow 
colour with picrocarminate of ammonia, are seen in the vesicles of many animals. 
Crystals sometimes occur in the gland vesicles (Tortoise and Rook) and brown 
pigment granules have been observed in the colloid material in the vesicles (Frog and 
Conger Eel). 
5. Parenchymatous cells, already described in the Dog, also occur in the glands of 
young Dogs and in less numbers in the Cat, in which animal they appear to migrate 
into the vesicles in the same manner as in the Dog. Large groups of round or oval- 
shaped cells, provided with a single nucleus, frequently occur in the thyroid gland of 
the Pigeon. 
6. A netwurk of lymphatics resembling in its general characters that previously 
described in the Dog, though differing apparently in the extent of its ramifications, is 
also seen in some other Mammals. The homogeneous or granular contents of the 
lymphatics in the Dog occur in both injected and in uninjected specimens and in very 
variable quantity ; the amount being apparently independent of the sex or age of the 
animal. 
In the thyroid gland of Birds (Pigeon) no system of lymphatics is injected by the 
method of puncture, but the injecting fluid enters the blood-vessels of the gland, 
escaping by the jugular vein. 
The thyroid gland of the Tortoise contains a network of lymphatics, of which the 
smaller ramifications run between almost all individual vesicles. The endothelium of 
these lymphatics presents well marked areas of irregular size and shape, stained darkly 
with nitrate of silver. In the thyroid gland of the Conger Eel no evidence of a system 
of lymphatics was obtained by injections. 
7. The arteries are ensheathed more or less completely in their accompanying 
lymphatics (Dog, Tortoise); the capillaries, on the contrary, run between the epithelium 
of the vesicles and the smallest ramifications of the lymphatics (Tortoise) leaving 
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