62 THE ROYAL SOCIETY OF CANADA 
Histology of the Thyroid. 
The thyroid of the frog consists of a number of closed vesicles, the 
walls of which are lined with a single layer of small, low, cubicalepithelial 
cells. The vesicles are small as compared for example with those of some 
of the cartilaginous fishes, though individual vesicles vary considerably 
in size. The intervesicular material is to a large extent formed of 
fibrous connective tissue with scattered nuclei and blood-vessels, and 
has comparatively few cellular elements. 
Historical. 
As pointed out by Gaupp' the ventral branchial body has frequently 
been described as the thyroid. This mistake was first made by Carus? 
(1818) and by Huschke*® (1828). A similar view was put forward by 
Simon“ (1844) and Leydig® (1852). The latter author also placed the 
two parathyroids in the same category, though he observed that all 
these structures differed considerably from the typical thyroid of 
vertebrates. Fleischl® also described the ventral branchial body as the 
“so called thyroid of the frog.”’ Toldt? pointed out that none of these 
bodies could be correctly called thyroid and came to the conclusion that 
there was no true thyroid in batrachians. The true thyroid of the frog 
was apparently first seen and described by W. Müller (1871). Fuller 
descriptions were given by Baber* and Maurer.” 
Since this time the organ has been frequently described. 
Development. 
The development of the thyroid in Rana temporaria has been 
worked out by Miller" and confirmed by Gætte®? for Bombinator, by de 

1 Loc. cit. 
? Lehrbuch der Zootomie, Leipzig, 1818. 
3 Ueber die Umbildung des Darmeanals u. d. Kiemen der Frosch-quappen. 
Isis von Oken. Bd. 20, 1827. 
# Phil. Trans. R.S. of Lond., Pt. 2, 1844. 
5 Frorieps Tagesber ü. d. Fortschr. u. d. Natur. und Heilkunde, Abtheil f. Zool. 
u. Palaont. Bd. 2, 1852. 
8 Sitzungsber. d. K. Akad. d. Wissensch., Wien Math.-naturw. Cl., vol. 60, 
Sect. 2, 1869, 1870 (Wien). | 
7 Sitzungsber. d. K. Akad. d. Wissensch, Wien. Math. naturw. Cl., Bd. 58, 
Abth. 2, 1868. 
8 Jenaische Zeitschr. f. Med. u Naturw. Bd. 6, 1871 
® Phil. Trans. R.S. of Lond., Vol. 172, Pt. 3, 1882. 
10 Semon, Zoolog. Forschungsreisen, Bd. 3, 1899. 
4 Jenaische Zeitschr. f. Med. u. Naturw. Bd. 6, 1871 
12  Eingeweidelehre in Allgemeinen”’ N. 4. 

