180 SPECIAL HISTOLOGY. 



sur la structure intime du Poumon, Brux./ 1846 ; A. Adriani, 

 ' De subtiliori pulmonum structural Trajecti ad Rhen. 1847, 

 Diss. ; Kostlin, ' Zur normalem und patholog. Anatomie der 

 Lungen/ in Gries. 'Archiv/ 1848, Heft IV, p. 282, and 1849, 

 Heft II, p. 167 ; E. Schultz, ' Disquisitiones de structura et 

 textura canalium aeriferorum/ cum tab., Dorpati Liv. 1850. 

 Dissert.. 



OF THE THYROID GLAND. 

 § 180. 



The thyroid gland, or body (glandula thyroidea), is a so- 

 termed l ductless gland/ which in its external aspect much re- 

 sembles the racemose glands, seeing that its round, closed 

 gland-vesicles j ^ — ~" in size, are surrounded by a fibrous stroma 

 and subdivided into rounded or elongated, often slightly poly- 

 gonal lobules, i — J'" in size, — the gland-granules of authors ; — 

 and these again are associated into larger, though not com- 

 pletely separated, lobes, out of which the main divisions of the 

 organ are then constituted ; these have special, and indeed 

 thicker coats, with which, lastly, a fibrous membrane investing 

 the whole organ is conjoined. 



§ 181. 



With respect to its intimate structure, there is not much to 

 be said about the fibrous tissue or stroma of the thyroid gland, 

 inasmuch as it consists of common interlaced bundles of con- 

 nective tissue, intermixed with fine elastic fibres and also, on 

 the surface, contains a certain quantity of fat-cells. The gland 

 vesicles themselves, in Man, present such varied conditions of 

 structure, that it is not easy to say what is their normal state. 

 According to what I have observed in Man and also in ani- 

 mals, I must, with regard to this point, declare that, analogous 

 to the true gland vesicles, for instance, of the mucous glands, 

 they consist of a membrana propria, an epithelium, and 

 fluid contents. The membrane is quite homogeneous, trans- 

 parent, and delicate, 0-0008'" thick; and, like all membranes 

 of the sort, is rendered more distinct by caustic alkalies, 

 in which it swells up. On its inner surface lies a single 

 layer of epithelium, composed of polygonal, finely granular, 



