Page:Natural History Review (1861).djvu/490

478 sufficient confidence; but as I have succeeded in injecting a minute network of vessels on the stomach in one instance, and that not under the most favourable circumstances, I cannot doubt that the peripheral portion of the vascular system is as complete as the central, and that I shall be able to demonstrate this so soon as I shall obtain suitable and fresh specimens. Neither must we forget that Kölliker (Entwickelungsgeschichte der Cephalopoden), states that he has observed capillary vessels in the embryo of Sepia, and that H. Müller describes them. We may therefore, I think, fairly assume, for the present, that the vascular system is throughout supplied with proper walls. And here the question naturally arises, How then does the chyle enter into the circulation?

From whatever point of view we look at this important question, we find it beset with difficulties. Supposing, for instance, that we adopt the opinion of Milne Edwards, that the great dorsal blood sinus is nothing more than a visceral chamber, more or less developed, forming an extensive hiatus in the continuity of the vascular system, it is not easy to see how the chyle could find its way into this reservoir, even were it devoid of walls. In those mollusks which have the intestine floating in the visceral chamber, the chyle may be supposed to exude through the walls of that tube, and thus at once pass into the circulation. But in the Cephalopoda the intestine is not so situated. On the contrary, it is placed on the ventral, or opposite side of the body, having the liver above it. It is not, however, in contact with that viscus, but is separated from it by a stout muscular membrane, which entirely cuts the intestine off from all communication with every portion of the so-called visceral chamber. In fact, in most of the Loliginidæ, the greater portion of the intestine is placed, along with the great cephalic vein and duct of the ink-bag, in a confined space, bounded above, by this membrane, below, by the external wall of the abdomen, and behind, by that of the renal chamber: in front, the space is closed by the coalescence of the said membrane and the abdominal wall. And here the intestine lies closely packed in juxta-position with the above-mentioned organs; the whole being bound together and firmly attached to the surrounding walls by areolar tissue. In the Octopodidæ, the intestine is also to a great extent similarly situated; but the convoluted portion is thrust further back between the wall of the renal chamber and that of the right side of the abdomen. How, then, the chyle is to find its way from the intestine to the so-called visceral chamber it is impossible to say. Milne Edwards does not explain how this is effected: on the contrary, his injections prove that the visceral chamber is bounded by a wall, and is entirely cut off from the space in which the intestine is placed.

The difficulty is not much lessened by assuming the absence of capillaries; for nearly all the viscera, whose veins might be supposed to take up the chyle mingled with the extravasated blood, are confined in chambers which are equally cut off from the space in which