The Pharyngeal Pouches in the Mammalia 239 



The median thyroid has moved backwards to a position immediately 

 in front of the trachea (Figs. 23, 25), Its lateral wings have grown 

 back over the outer side of the lateral thyroids, the latter thus being 

 partly embedded on their inner sides. 



An exceedingly fine duct still connects the lateral thyroid with the 

 pharynx. 



The dorsal process (Gl.T.) forms a small spheroid attached to the 

 remains of the duct. It is clearly composed — like the carotid gland — 

 of a close network of solid follicles, the interstices of which are traversed 

 by a system of capillaries (Fig. 54). 



A cat of 15 mm. (Pig. 65) shows each lateral thyroid embedded in a 

 depression on the inner side of the corresponding lateral wing of the 

 median thyroid. Its minute structure is easily distinguishable from that 

 of the latter organ by its solid lymphoid character. 



A "glandule thyroidienne" does not appear to be present. 



In a pig of 24 mm. the lateral thyroid is also largely surrounded by 

 and embedded in the lateral wing of the thyroid. Only its more dorsal 

 portion projects above the latter (Pig. 29, La.T.). 



The "glandule thyroidienne" is present, at least on the right side. I 

 found no clear trace of it on the opposite side. 



In a 25 mm. pig conditions are similar to those just described, but 

 both glands are present. That on the left, however, is much reduced, 

 being only about a fifth the size of that on the right. I may add that 

 the same difference in size between the glandules of the two sides was 

 noticed in an 18 mm. pig. 



In a 23.1 mm. cat the lateral thyroid bears the same relation to the 

 lateral wings of the thyroid as in the pig last described. I could, how- 

 ever, find no readily distinguishable traces of the "glandule thyroid- 

 ienne." 



In a 31 mm. cat such lateral thyroid is deeply embedded in a con- 

 cavity on the inner surface of the corresponding wing of the thyroid. 

 No part of it projects beyond the periphery of the latter at any point. 



Two minute bodies (Pig. 68) were observed, one on each side, close 

 to the lateral border of the oesophagus. They apparently correspond in 

 position with the glandules, but, as I could not readily determine their 

 minute structure in the specimen examined, I think it improbable that 

 they represent these. They are probably independent structures, lym- 

 phatic in origin. 



In a 21-day rabbit the lateral thyroid forms a solid, ovoidal mass 

 deeply embedded in a flask-shaped depression on the inner side of the 



