THYROID GLAND OF MAMMALIA. 565 



scapula and humerus, covered by the panniculus carnosus and 

 the trapezius, present a reddish colour, a lobulated structure, and 

 pretty firm texture, and seem to represent the thyroids. These 

 are in more constant relation to the windpipe, in Marsupials : 

 they are two disunited bodies in the Dasyures ; each presenting 

 the size of a horse-bean in the Das. macrurus. They were of the 

 same size in a Phalangista fuliginosa, but were united by a fila- 

 mentary strip passing between their lower extremity, across the 

 first tracheal ring. In the AVombat I found two elongated thyroid 

 bodies of a dark colour reaching from the thyroid cartilage to the 

 seventh tracheal rinar on each side. In the Koala they were 



o ' 



situated lower down, extending from the fourth to the ninth or 

 tenth tracheal ring. 



The thyroid is relatively small in the Kangaroo. It presents 

 more normal proportions in Rodents, but is connected by very 

 lax areolar tissue to the trachea. Each bodv is elongate and 



/ O 



almost cylindrical, but expanding at the lower end, where they 

 are joined by a thin band, in the Hare and Rabbit. The uniting 

 band is thicker and rounded in Rats and Marmots ; but appears 

 to be wanting in Geomys and Batkycryus. The thyroid bodies 

 are commonly ununited in Cheiroptera. They lie, similarly de- 

 tached, but low down, opposite the sixth and seventh tracheal 

 rings, in the Elephant. They are also separate and more remote 

 from the larynx in Delphinidce. Cuvier notes them as rounded 

 and separate in the Hyrax. 1 In the Rhinoceros I found them 

 joined together by a very thin and narrow strip continued be- 

 tween their hinder ends, obliquely across the trachea. Each 

 body was elongate, subtriangular, extending from the sides of the 

 larynx to the fourth tracheal ring, and diminishing as they 

 descended: a small compact yellow body was attached to the 

 thyroid at the point of emergence of the vein. In the Horse, 

 also, I find the thyroids connected by a slender band crossing the 

 second tracheal ring: 2 each body is egg-shaped and united about 

 one-third from the lower end. The thyroids are relatively smaller 

 in the Ass, but are similarly united to each other. 



In the Llamas (Auchenia) the thyroids are oval, with the great 

 end downward, extending from the side of the thyroid cartilage 

 to the third tracheal ring, where they are connected together 

 by a filamentary band : this band is relatively broader in the 

 true Ruminants, in most of which the thyroids have a more 



1 I regret that I omitted to note the condition of the thyroid in CLIII". 



2 Cuvier describes them as ' entitlement separes, et situes bien au-dessous du 

 larynx.' xii. torn. viii. p. 677. 



