280 



Mr. E. C. Baber. 



[Jan. 6, 



observed has been a delicate layer of connective tissue between the 

 epithelium and the endothelium of the lymphatics, in which the 

 capillaries ramify. 



(3.) Contents of Vesicles. — The following are the chief constituents 

 of these which have been observed in the microscopical examination 

 of specimens hardened in alcohol : — 



(a.) Homogeneous or granular material (" colloid substance " of 

 authors) has been observed with slight variations, in all classes of 

 the vertebrata, and is undoubtedly a normal product of the organ. 



(b.) Bed Blood-corpuscles are frequently found in the vesicles in 

 greater or less number, and in various stages of disintegration and 

 decolorisation. In the epithelial wall of vesicles containing red blood- 

 corpuscles granules of yellow pigment are sometimes seen which 

 appear to be due to the absorption, by the epithelial cells or inter- 

 cellular 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 pas- 

 sage of red blood- corpuscles into the vesicles is a normal occurrence in 

 the thyroid gland. Further observations (dog, rook, seal) also make 

 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, the 

 author considers, 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 blood-corpuscles (large round cells, with granular 

 cell-substance and single round or oval-shaped nucleus) are frequently 

 seen in the homogeneous material in the gland-vesicles of the tortoise. 

 The migration of these cells into the vesicles is a normal occurrence in 

 this animal. It may also take place in other animals. 



(c2.) Bounded masses staining darkly with haematoxylin, or of a 

 bright yellow colour with picro-carminate of ammonia, are seen in the 

 vesicles of many animals. Crystals sometimes occur in the gland- 

 vesicles (tortoise, rook), and finally brown pigment granules have been 

 observed in the colloid material contained in the vesicles (frog, 

 conger-eel). 



(4.) Parenchyma. — The parenchymatous cells already described in 

 the adult dog have been observed in the glands of dogs a few weeks 

 old. In the cat parenchymatous cells have been seen in less numbers, 

 and they appear to migrate into the vesicles in the same manner as in 

 the dog. In the pigeon large groups of round or oval-shaped cells, 

 provided with a single nucleus, are frequently seen, but there is no 

 evidence to show that they migrate into the vesicles. 



