604 
MR. E. C. BABER ON THE STRUCTURE OF THE THYROID GLAND. 
intervals between tliem, where the lymphatic is not separated from the epithelium by 
blood-vessels. Projections of the capillaries between the epithelial cells towards the 
cavity of the vesicles occur frequently in the Tortoise. In the Pigeon the inter- 
vesicular ramifications of the blood-vessels are not so complicated or minute as in 
other animals (Sheep, Tortoise) but resemble more the distribution of lymphatics 
in some Mammals. The veins, in the Pigeon, frequently surround either partially or 
entirely the arteries which they accompany. 
8. Bodies consisting of portions of the gland of which the development has proceeded 
no further than the stage of convoluted “ cylinders of cells ” described by W. Muller 
are frequently seen in the thyroid gland. The cylinders are composed of cubical or 
columnar cells, resembling epithelial cells, those on the surface of the cylinder being 
arranged at right angles to the capillaries, which ramify between the cylinders. In 
Dogs aged three months and upwards these “ undeveloped portions ” usually form dis¬ 
tinct bodies separated by layers of connective tissue from the rest of the gland. In 
young animals, such as the Kitten, they are often continuous with the ordinary 
gland-tissue into which they are evidently developing. 
In conclusion, I wish to offer my best thanks to Dr. Klein for his direction in this 
research, which has extended over a period of several years. 
Explanation oe the Plates. 
PLATE 68. 
Fig. 1. Transverse section of a portion of the neck of a moderate sized Frog, on a 
level immediately anterior to the convergence of the hyoglossus muscles. 
(Y erick’s obj. 0, oc. I. All the lenses employed in these drawings were 
Yerick’s, except an obj. F of Zeiss.) 
1. Hyoid cartilage. 
2 . 2 . Thyroid glands, situate directly on the ventral surface of the hyoid 
cartilage. 
3. Hyoglossus muscles seen in transverse section. 
Fig. 2. Outline of a branched vesicle from a longitudinal section of the thyroid 
gland of a Puppy (aged 5 weeks) hardened in alcohol. The section from 
which this was taken was purposely very thick, and the different portions 
of the vesicle, which are situate on different planes, can only be brought into 
view by repeatedly altering the focus. The epithelium is semi-diagrammatic. 
(Obj. F, oc. I.) 
Fig. 3. From a transverse section of the thyroid gland of a Dog (aged 3 months) 
hardened in alcohol. Showing the outline of a branched gland-vesicle. This 
body appears at first sight to be composed of three distinct vesicles, but on 
focussing the continuity of these three can be traced at i, i. (Obj. 6, oc. I.) 
