466 SCHULTE, SEI WHALE. 



The lumbar segmental arteries are peculiar in that each pair arises by a single trunk from the 

 aorta. The ventral branches in the abdomen are the coeliac, superior mesenteric, and inferior 

 mesenteric. The first two arise in close proximity immediately below the diaphragm. The 

 coeliac divides into a hepatic and gastric, from which latter the small splenic branch is derived. 

 The inferior mesenteric is a very small vessel arising but a short distance above the hypogastrics. 

 Of the ventrolateral series, inferior phrenic, adrenals, renals and sex arteries were found. Of 

 the latter two pairs seemed to be present. The inferior were large and arose opposite the 

 inferior mesenteric, the superior were large and situated below the poles of the kidneys. Their 

 course carried them into the base of the folds on the dorsum of the ligamentum latum, which 

 ascend to the ovaries. The hypogastrics are of minute size and arch ventrad to the sides of the 

 bladder, where they ascend to the umbilicus, being invested and attached to the bladder by a 

 thick sheath, which Daudt finds to be muscular. From the arch of the hypogastric a large 

 trunk is given off, which entering the foramen in the rectus, divided into a large ascending branch 

 to the rectus muscle, deep epigastric, and a descending vessel which is distributed to the pelvic 

 viscera and muscles. 



The arteries are distinguished by the enormous thickness of their wall. In the ascending 

 and transverse aorta, the lumen is reduced to a mere slit between two longitudinal cushion- 

 like ridges, which ascend with a spiral curve from the region above the sinuses of Valsalva. Not 

 until it receives the ductus arteriorus does the aorta attain a circular lumen. The sinuses of 

 Valsalva are deep and narrow. They are not visible externally. 



The pulmonary artery is wide and short. Its wall, though very thick, is less than that 

 of the aorta, and its circular lumen appears more capacious. The right pulmonary artery has a 

 very oblique descending course, grooving the right atrium between the orifices of the cavse. 

 It gives off its apical branch as it crosses the primary bronchus. The left is nearly transverse 

 and much shorter than the right, and is distinctly diminished in diameter after giving off the 

 ductus arteriosus. 



Venous system. The systemic venous return to the right auricle is effected by a postcava 

 and a single precava. The arrangement of the great veins at the root of the neck and in the 

 upper mediastinum is of the common asymmetrical type resulting from the suppression of the 

 left precava and has no peculiarity of first importance save in the reduction and modifica- 

 tion of the azygos veins. The great vessels here considered have wide lumina and walls which 

 are thin but not excessively so; the internal jugular veins are especially capacious and stand in 

 marked contrast to the small subclavia. These trunks unite at the ventral margin of the scalene 

 to form the brachiocephalica, which are appreciably less in cross-section than the sum of the 

 cross-sections of the confluent vessels. The same is true in higher degree of the precava as com- 

 pared with the two brachiocephalicse. The left of these veins has a very oblique course within 

 the thorax resting upon the thyroid gland and the arch of the aorta and having the thymi on its 

 caudal aspect, from the interval between which it receives the large thymic vein. The right 

 brachiocephalica runs directly caudad. At the level of the dome of the pleura a large vessel 

 joins the brachiocephalic of each side. This accompanies the posterior thoracic artery, drain- 

 ing its plexus, but in addition by a large spinal tap affords an outlet to the intravertebral plexus. 

 The precava is very short and immediately enters the pericardium, within which it turns ventrad 

 and slightly to the left. The angle its ventral wall makes with the auricle is deepened to a 

 narrow cleft, which marks the rostral extremity of the sulcus terminalis. 



