" The subclavian artery in the Piked Whale, before it passes over the first rib, sends down into the chest arteries which assist in forming the plexus on the inside of the ribs ; I am not certain but the internal mammary arteries con tribute to form the anterior part of this plexus. The motion of the blood in such cases must be very slow ; the use of which we do not readily see. The descending aorta sends off the intercostals, which are very large, and gives branches to this plexus ; and when it has reached the abdomen it sends off, as in the quadruped, the different branches to the viscera and the lumbar arteries, which are likewise very large, for the supply of that vast mass of muscles which moves the tail.
" In our examination of particular parts, the size of which is generally regulated by that of the whole animal, if we have only been accustomed to see them in those which are small or middle-sized, we behold them with astonishment in animals so far exceeding the common bulk as the Whale. Thus the heart and aorta of the Spermaceti Whale ap peared prodigious, being too large_ to be con tained in a wide tub, the aorta measuring a foot in diameter. When we consider these as applied to the circulation, and figure to our selves that probably ten or fifteen gallons ,of blood are thrown out at one stroke, and moved with an immense velocity through a tube of a foot diameter, the whole idea fills the mind with wonder." '11 It is to be presumed, as has been done, that this singular complication of vessels is caused by the necessity in which the Cetaceans are often placed of suspending their respiration, and consequently the oxygenation of their blood, during a considerable time. These numeerous arteries form, therefore, a reservoir of oxyge nated blood, which, re-entering the circula tion, supports life throughout, where venous blood would only produce death. But how this blood is sent to this general system of arte ries, or what is the peculiar force which acts upon it to this effect, is a point on which we are still reduced to the most vague conjectures.
The disappearance of the posterior members bas occasioned that of the vessels which should nourish those members ; and as the tail has attained a considerable development, the arte ries and veins which belong to this last part of the trunk have been developed in the same proportion. The abdominal aorta does not send off any external iliacs, but is continued underneath the tail in the canal of the inferior processes, from whence its ramifications are dis tributed to the muscles which move this organ.
The modifications of the venous system are in many respects analogous to those of the arteries.
The quantity of blood contained in the vascu lar system appears to be proportionally much greater than in the other Mammalia.
[In the Porpesse the veins are almost univer sally devoid of valves, so that they can be as easily injected from trunks to branches, as in the reverse direction. The plexiform disposi tion which we have seen to characterize so many parts of the arterial system is still more strongly displayed in the venous. Thus in the system of the anterior vena cava, with the ex ception of the trunk of that vein itself, and the short jugular veins which join it, an internal and an external jugular branch, and a pair of large subcutaneous veins, all the other parts of tne system manifest the plexiforrn disposition. This is most remark able in the large venous sinuses surrounding the central axis of the nervous system, which receives the intercostal veins, and by means of which the system of the anterior cava is chiefly brought into com munication with that of the pos terior cava ; for, as V. Baer has observed, there is no intercommu nicating channel analogous to the vena azygos of the higher Mam - malia.
Of the venous plexuses belong ing to the system of the inferior cava, that which is found at the posterior parietes of the abdominal cavity extending from below the kidney to the lower boundary of the abdomen is the most remark able, and we have selected in illustration of this, the figure from Baer's excellent memoir on the vas cular system of the Cetacea.s In this figure (fig. 266) the anterior parietes of the abdomen are remo ved. The two immense lateral de pressor muscles of the tail are seen at A, A, and B shows their point of convergence to be iuserted into the inferior spinous processes, by which the cavity of the abdomen is contracted and defined posteriorly. Just anterior to this commissure is seen the termination of the rec tum H. C, C, are the two ischia. D, D, the posterior parietes of the chest projecting forwards over the abdomen. On the right side the kidney and the peritoneum are re moved; on the left side they are seen in situ, and also a part of the left cornu of the uterus G, with the oviduct and ovary K.