THYROID GLAND. 



[ 641 ] 



TINEA. 



THYROID GLAND.— The thyroid gland 

 is one of the vascular glands^ or glands with- 

 out ducts. 



It consists of rounded, closed, glandular 



Fig. 750. 





i;\ 



Glandular vesicles from the thyroid gland of a child. 

 a, intervening areolar tissue; b, basement membrane; 

 c, epithelium. 



Magnified 250 diameters. 



vesicles (fig. 750), surrounded by or imbedded 

 in a fibrous stroma (a), and aggregated into 



Fig. 751. 



Glandular vesicles with colloid matter. 

 Magnified 50 diameters. 



roundish, elongate, or somewhat polygonal 

 acini or minute lobules, these being grouped 

 in secondary lobules, which unite to form 

 lobes. The vesicles are from 1-600 to 1-240" 

 in diameter, the acini from 1-50 to 1-24". 

 The stroma is condensed around the lobules, 

 to form a fibrous coat. 



The stroma consists of ordinar}^ interlacing 

 bundles of areolar tissue, with fine elastic 

 fibres; at its outer surface containing fat- 

 cells. 



The vesicles consist of a basement-mem- 

 brane (fig. 750 b), lined by a single layer of 

 polygonal epithelial cells (c), and containing 

 a yellowish, tenacious, albuminous liquid. 



The capillaries form plexuses surrounding 

 the vesicles. 



In goitre, the vesicles become greatly en- 

 larged, and confluent, so as to form cysts 

 containing colloid matter, with fat-globules 

 and cr3stals of cholesterine. The same con- 

 ditions, in a minor degree, are so frequently 

 met with, that they can scarcely be regarded 

 as abnormal. The epithelium is also often 

 found loose in the vesicles (fig. 751). The 

 minute arteries and capillaries are often 

 found varicose. 



BiBL. Kolliker, MiJcrosJc. Anat. ii. 327 ; 

 Forster, Pathol. Anat. ii. 233. 



THYSANURA.— An order of Insects, to 

 which Lepisma and Podiira belong. 

 See Insects (p. 362). 

 TILLETIA, Tulasne.— A genus of Usti- 

 laginei (Coniomycetous Fungi), forming the 

 Bunt, a kind of blight of various corn grains, 

 in which the ears are attacked, and the in- 

 ternal substance of the grains is replaced by 

 a fcetid, black powder, consisting of the 

 spores of the fungus. T. Caries ( Uredo Ca- 

 ries, D.C.) attacks wheat and other grain. 

 The interior of the ovaries of the corn is at 

 first occupied by an interwoven mycelium, 

 from which the globular spores arise on 

 short stalks ; as the latter grow, the ears 

 become more or less deformed, the my- 

 celium disappears, and the spores are set 

 fi-ee as a pulverulent mass ; the spores have 

 a reticulated surface, and their pedicel is 

 often found attached. (See Ustilaginei.) 

 BiBL. Berk. Brit. Flor. ii. pt. 2. p. 375; 

 Tulasne, Ann. des Sc. nat. 3 ser. vii. p. 112. 

 pi. 5, 4 ser. ii. p. 161. 



TIMMIA, Hedw. — A genus of Mniaceous 

 mosses, containing one British species, 

 Timmia austriaca, Hedw. {megapolitana. 

 Hook, and Tayl.). 



TINEA, Fabr. — A genus of Lepidopterous 

 Insects, of the family Tineidse. 



2t 



