Page:Natural History Review (1861).djvu/491

Rh the intestine is placed. The venous radicles of the abdominal walls in the vicinity of the intestine might possibly absorb the chyle; but the anatomy of the parts shows nothing to warrant such an opinion.

After weighing this point with much care, I am forced to the conclusion, which must have been generally adopted when the macular system in the Mollusca was thought to be complete, that the absorption is effected through the instrumentality of the intestinal veins themselves, which are amply provided, and are every way suitable, for such a purpose. There are usually two or more such veins; and in the Loliginidæ they are placed symmetrically, on each side of the alimentary tube, and have the portions which lie within the renal chamber covered with glandular appendages, similar to those that garnish the venæ cavæ. They always open into the venæ cavæ, or into the great cephalic vein, close to the point where the latter gives origin to the former, and are richly provided with twigs.

Now, it would seem that it must be through the agency of the capillaries of these vessels that the chyle, or nutritive fluid, finds its way into the circulation. These capillaries probably penetrate to the folds of the mucous membrane that lines the intestinal tube, and there assuming the office of lacteals, in addition to that of veins, take up, by a species of endosmosis, the nutritive products of digestion. Or, it may be that, spreading out over the surface of this portion of the alimentary tube, they there meet with and absorb the exuded chylous fluid.

There is nothing that should startle us in the idea that these veins act in a double capacity, for everywhere throughout the animal kingdom we observe one and the same organ performing several functions, until the division of labour in organic life is fully consummated. And in the embryo of the higher animals the absorption of the nutritive matters is actually effected by the sole agency of the vascular system. Thus, in the embryo of the fowl, the yolk is absorbed by the blood-vessels of the germinal membrane; and the nourishment of the mammalian embryo is accomplished by the aid of the vascular tufts of the umbilical vessels, which likewise absorb the required oxygen from the blood of the parent. So that, in the latter case, these blood-vessels do not only act as lacteals, but also perform the function of lungs.

The chyle, then, in the Dibranchiate Cephalopoda appears to be absorbed in this way by the intestinal veins, and to be poured by them, mixed with the blood coming from the intestinal tube, into the venæ cavæ, and there commingled with the blood returning from all parts of the system, to be subjected, on its way through the branchial hearts to the aerating organs, to the action of the renal follicles.

These hearts are of a very peculiar appearance; so much so that their cardiac nature has been denied. Their walls are exceedingly thick, soft and spongy, and are composed, for the most part, of nucleated granular cells. On this account they are considered by