THYROID GLANDS IN THE CETACEA. 321 
bone of the sternum, and immediately in front of the upper end of the peri- 
eardium. Their apices projected above the sternum into the lower part of the 
neck, lying in front of the trachea, and extending upwards almost as far as the 
lower margin of the median portion of the thyroid gland, from which they were 
separated by the innominate vein. From each of these lobes a long process of 

The Thyroid and Thymus Glands of the well-grown male porpoise, About one-third the natural size. 
The relation of these glands to the wind-pipe, the pericardium, and to each other, is represented. 
glandular tissue extended deeply between the structures situated at the root of 
the neck. That from the right lobe passed in front of the trachea, being in close 
contact with the anterior surface of that tube, to the left side, where it became 
connected to the deep process from the left lateral lobe. This transverse com- 
municating portion extended behind the arch of the aorta, so that this vessel, 
with its ascending carotid branches, was situated between the deeper and more 
superficial parts of the gland. Connected with the upper margin of the deep 
process from each lateral lobe was an elongated portion, which extended upwards 
on each side of the neck as far as the thyroid cartilage, being in close relation 
with the carotid vessels. These ascending prolongations of the thymus were thus 
brought into intimate relation with the lateral portions of the thyroid, so that 
at first it appeared as if they formed a common glandular mass with them. On 
a closer examination, it was found that they were not continuous, but intimately 
connected together by a little cellular tissue, on dividing which, the two glands 
could be separated from each other, without effecting any injury to their proper 
structure. 
On referring to that part of Mr Sron’s essay,* which treats of the com- 
* Physiological Essay on the Thymus Gland, 1845. 
