DR. J. MURIE ON THE ANATOMY OF THE WALRUS. 431 
apart at the fundus, a short distance behind the neck. A ridge of membrane is con- 
tinued from each, which join at the ejaculatory ducts. 
VY. VASCULAR AND RESPIRATORY SYSTEMS. 
1. The Heart.—Such a careful and accurate description of the heart has already been 
given by Owen', that repetition on my part is unnecessary; but I may mention the 
appearances of this organ after having been fully distended with plaster of Paris by my 
former colleague and friend Dr. J. Bell Pettigrew*. The preparation made by him is 
now exhibited in the Gallery of Physiology, in the Hunterian Museum. Altogether 
the heart is of immense size. The base of the ventricles is quite a foot across, the 
length from root to apex 8 inches high, and 13 or 14 inches if measured to the summit 
of the arch of the aorta. ‘The tip of the right auricle, as Owen remarks, comes 
forward; but the rest of the auricular cavity is rather thrust backward. The post- 
caval or descending vena cava is double in this specimen, though found single in the 
animal cut up by Owen. 
The coronary or great cardiac vein is very large, and follows the mesial ventricular 
furrow obliquely towards the apex. 
2. Arterial Distribution—The aortic arch and vessels springing therefrom verify 
Owen’s observations. The arch has a capacious thick-walled dilatation opposite the 
obliterated ductus arteriosus, where it diminishes very rapidly in calibre, as it forms the 
descending aorta. The innominate artery, the right and left common carotid, and the 
left subclavian vessels are derived separately from the summit of the arch. The innomi- 
nate artery is wide, and about 14 inch long. The internal mammary branch and the 
vertebral artery are sent off nearly opposite each other; the former, from the lower 
border, descends into the thorax outside the inferior vena cava; the latter, starting from 
the upper border, rather behind, proceeds obliquely outwards and upwards, crossed by 
the pneumogastric nerve as it goes to the chest. 
Immediately beyond the vertebral a large suprascapular artery comes off from the 
upper border of the innominate, and, crossing the lower cervical plexus, trends outwards 
and upwards to supply the muscles of the neck and the back of the scapula. The con- 
tinuation of the innominata is by a wide subclavian. The right carotid, starting rather 
in front of the right subclavian, obliquely curves over the root of the trachea, and runs 
forward in the neck; the left, which springs almost adherent and, if any thing, behind 
the right, goes up the neck in a nearly straight direction. 
The left subclavian, half an inch apart from the last, nearly equals the innominata 
in diameter as well as in length. The left internal mammary and the vertebral arteries 
start contrariwise from the parent trunk, almost in the same manner and position as on 
' P. Z. 8. 1853, p. 104. 
2 Tate first Assistant in the Hunterian Museum, now Pathologist to the Edinb. Roy. Infirmary, and Con- 
servator Roy. Coll, Surg. Edinb, 
