MR. E. C. BABER ON" THE STRUCTURE OE THE THYROID GLAND. 
589 
lymphatics, and on this are observed fine wavy striae, which are evidently due to a 
delicate layer of connective tissue interposed between the endothelium and epithelium 
in which the capillary blood-vessels ramify (see Plate 68, fig. 7). Judgingfrom the 
appearance presented by this layer of connective tissue when examined from the 
surface, it is probable that it forms a continuous layer even at points where the 
lymphatics are not separated from the epithelium by capillaries, although in vertical 
sections I have not been able to trace this layer at these points. I have not observed 
any other form of basement membrane, nor have I been able to detect by maceration 
in Muller’s fluid, any basement membrane resembling the “ Driisenkorbe ” described 
by Boll. 
III. Contents of Vesicles. 
Literature. — Frey and Peremeschko describe the contents of the vesicles in the 
embryo as consisting of a finely granular substance in which cells and nuclei are 
embedded. Peremeschko figures these cells and says that they differ from the 
epithelial cells by their round shape and smaller nuclei. He finds that in larger 
embryos vesicles filled with colloid masses are met with here and there. In young 
animals the greater part of the vesicles are filled with this mass, and finally in adult 
animals it is very rare to meet with vesicles without colloid. 
Kolliker speaks of the contents of the vesicles in the healthy human thyroid gland 
as a clear, yellowish, somewhat tenacious fluid containing a large amount of albumen. 
Boechat alludes to the cavities as being first partly filled with a fluid of viscid 
appearance in which float granules in more or less abundance. Zeiss describes the 
small vesicles as being first filled with a clear fluid, soluble in water, which is related 
to albuminous substances in its chemical behaviour, and considers that it is not 
essentially different from the colloid masses, which often accompany, and subsequently 
replace it entirely. Numerous ill-defined, granular disintegrating cells, remains of 
protoplasm and nuclei, are present in it, also fat granules, cholesterine and octohedral 
crystals of oxalate of lime. 
Almost all observers allude to these contents of the vesicles being subsequently 
replaced partly or entirely by a substance to which the term of colloid is applied. 
Colloid substance. —With slight variations this body is described as a homogeneous, 
transparent, more or less yellow substance (Virchow, Frey, Kolliker, Boechat), 
viscid in character (Virchow, Kolliker, Boechat), and completely filling the 
vesicles in the adult state (Frey). Peremeschko finds that it usually fills the whole 
vesicle, but that in other cases it appears as smaller or larger transparent drops 
adhering to the wall of the vesicle ; in still other cases it appears as smaller or 
larger transparent granules (sago-grains, Ecker) suspended in a finely granular mass. 
Amongst these granules (according to Peremeschko) are found occasionally, even in 
adult animals, the above-named cells, and stanes of transformation of these into the 
transparent colloid granules may be observed. 
