ANATOMY OP BALDEN OPTEEA EOSTEATA. 
245 
The aorta, after its origin from the left ventricle, was directed upwards and forwards, 
and at the sinus of Morgagni, which was well marked, it measured 3 inches in diameter ; 
its coats were a line and a half in thickness and highly elastic. The entire length of 
the arch was 8 inches ; it curved to the left side, immediately beneath the thymus gland 
and in front of the trachea. The arteria innominata arose from its first curve, corre- 
sponding to the upper border of the sinus of Morgagni ; it then ran forwards, outwards, 
and towards the right side, being crossed in front by the left vena innominata just as it 
was about to terminate by dividing into the right carotid and right subclavian arteries ; 
its entire length was 4 inches, and its diameter nearly 14 inch ; its point of division was 
situated about 4 inches above the first rib. The left carotid arose about 5 inches to the 
left of the arteria innominata ; it then ran upwards by the side of the thyroid body, 
where it measured about 1 inch in diameter, and continuing its course forwards for 
about 5 inches, terminated in the usual manner by dividing into the external and deep- 
seated branches. 14 inch still further to the left of the carotid the subclavian arose* 
and after a course of f of an inch it gave off three branches, viz. first, the vertebral, 
which ran directly forwards and outwards to the transverse process of the seventh cer- 
vical vertebra; second, the transversalis colli, which passed forwards and outwards; and 
third, the axillary, a small branch that passed outwards to supply the rudimentary 
anterior extremity. 
The descending aorta passed backwards into the posterior mediastinum, where it 
measured only 1 inch in diameter and gave off intercostal branches, twenty-two in 
number ; it then passed through the diaphragm into the abdomen, in which cavity it 
was continued backwards, finally terminating as caudal by being distributed to the 
muscles in this region. In this part of its course its branches presented no variation 
from the ordinary arrangement, with the exception that the superior mesenteric arose 
from the cseliac axis, a variety occasionally met with in the human subject. 
The main trunk of the pulmonary artery was 2f inches in diameter, its coats being 
about \ of an inch thick ; it passed to the left of the aorta, and after getting behind 
that vessel divided into the right and left branches. The large cord-like ligamentous 
remains of the ductus arteriosus was crossed by a cardiac branch of the pneumogastric 
nerve, which passed downwards in front of the aorta, between it and the pulmonary 
artery, to join the cardiac plexus. 
, Digestive Apparatus. 
No distinct superior pharyngeal constrictor was visible ; but a few scattered muscular 
fibres seemed to be substituted for it, having no very determinate course or attachment. 
In other Cetaceans, however, this muscle is present, as, for example, we found it in 
Globiocephalus Svineval. 
The middle constrictor was a flat fan-shaped expanded muscle ; it arose fleshy from 
the entire length of the posterior border of the great cornu of the os hyoides ; the fibres 
ran in a radiating manner, the anterior forwards and inwards, the middle directly 
inwards and the posterior backwards, all being inserted into the median raphe on the 
