THYROID GLANDS IN THE CETACEA. 323 
The close connection which I have now shown to exist between the thymus 
and thyroid glands in these porpoises, strongly indicates that they most probably 
have originated in a common structure. This view of the common origin of 
these elands was prominently announced by Professor Goopsir, in a paper in 
the Philosophical Transactions,* published many years ago. His investigations 
were conducted on the embryoes of sheep. He describes these glands as, together 
with the supra-renal bodies, developed from the remains of the blastodermic 
membrane extending along each side of the spine, from the Wolffian bodies to the 
base of the cranium,—a separation taking place between them in the process of 
development. 
The porpoise is not, however, the only mammal in which, in the non-foetal 
state, a connection may be seen to exist between the thymus and thyroid 
bodies. 
In a fine specimen of an adult male Hartebeest (Bubalus caama), in which I 
dissected some time ago these glands, I found the lateral lobes of the thyroid 
entirely separated from each other, and lying on the sides of the upper end 
of the trachea. Connected with the lower part of each of these lobes was a 
long slender process of gland substance, which descended 
along the sides and front of the trachea, until it reached the 
fourteenth ring, when the processes from each side became 
connected together. At this spot they united with another 
slender process of a similar structure, which descended from 
the sides of the larynx. The common gland-mass, formed 
by the union of these processes, now passed down the front 
of the trachea, and beneath the sternum, into the anterior 
mediastinum, undergoing, immediately above the sternum, a 
considerable augmentation in size. That portion of the struc- 
ture which was situated at the upper part of the trachea 
received its supply of blood from the arteries which supplied 
the thyroid gland. On examining this glandular substance 
microscopically, | found it to correspond in structure with 
the thymus gland, for it was essentially composed of numer- 
ous small circular corpuscles. Its structure and position 
warrant us in regarding it as a persistent thymus, and its 
close relation to the thyroid points to the conclusion that it | 
has been developed along with it. et coe Re 
In a dissection which I recently made of the thymus and 2 the Thyroid and of the 
slender processes of the 
thyroid in the Nylghau (Antilope picta), 1 obtained several pertinence hee 
very interesting facts connected with these glands. The _ size. 
animal which I examined was presented to the Anatomical Museum of the 
* On the Supra-renal, Thymus, and Thyroid bodies, 1846. 
VOL. XXII. PART II. 40 
Fig. 2. 

