In Loligopsis the venous follicles are in distinct groups, as in Nautilus ; and Rathke describes them as presenting a laminated and glandular structure.
With respect to the function of these bodies nothing is as yet definitely known. They are well supplied with blood from the neighbouring arteries, and are undoubtedly glandular ; but the matter which they secrete has not yet been subjected to chemical analysis. If the spongy coats of the vena cava of a Calamary be pressed, a whitish fluid escapes, which is al ways thicker and more turbid than the blood which circulates in the vein. The elongated cells of the Poulp yield in like manner an opake and yellow mucus. Some physiologists suppose that the secreted matter is not expelled by the orifices of the sacs into the veins to be mixed with the current of blood, but that the venous blood passes into the cells by those apertures, and that the matter secreted from it exudes from the parietes of the cells or follicles into the great serous cavity surrounding them. Mayer, considering that the urine is secreted from venous blood in the lower vertebrate animals, regards these venous appendages as the renal organs of the Cephalopods; the serous sacs (h, fig. 226), therefore, which Cuvier calls the great venous cavities,' and which we have termed the pericardium,' the German Physi ologist calls the urinary bladder;' and the papillary orifices (0 leading into the branchial or excrementory chamber, which we have com pared with the orifices leading from the peri cardium of the Ray and Sturgeon into the peritoneal cavity of the abdomen,t Mayer calls the urethrw. It must be observed, however, that this Physiologist does not advance any proof from chemical analysis in support of his theory. Cuvier, on the other hand, believing that the water of the branchial chamber might have access by the orifices to the cavities containing the appendages in question, supposes that they may serve as accessory respiratory organs. The valvular structure of the orifices is opposed, however, to this view; while it supports the doctrine of their being excretory outlets.
The venous follicles may, therefore, serve as emunctories, by means of *which the blood is freed of some principle that escapes from their external pores ; or they may alter the blood by adding something thereto ; or, like the spleen, they may assist in converting arterial to venous blood. As a secondary function they may
serve as temporary reservoirs of the venous blood whenever it accumulates in the vessels either from a general expansion, or from a partial impediment in its course through the respi ratory organs ; and thus the cells or follicles, which- are endowed with a motion of systole and diastole, like the auricles of the heart, may serve to regulate the quantity of blood trans mitted to the gills.
The branchial ventricles (d, d, fig. 225) are appended to the roots of the gills : in the Octo poda they are simple pyriform muscular cavities (k, k, fig. 226,) generally of a blackish grey co lour ; in the Decapoda they are elliptical or trans versely oblong, of a light grey or pale red co lour, and have a white fleshy appendage (e, e, fig. 2250 hanging to their lower surface or their external side. The connecting pedicle is hollow, and communicates with a small cavity in the substance of the appendix. Internally these ventricles are deeply impressed with cells and decussating carnew columnT (k, fig. 226), and where they com municate with the ve nous sinus two semi lunar valves (/) are placed to prevent re gurgitation. Their func tion is to accelerate the circulation throUgh the branchiw ; and by this simple addition to the respiratory appa ratus, the two gills of the Dibranchiata are rendered equal to the office of preparing the blood to maintain the increased muscular ex ertions, and repair all the corresponding waste which the vital economy of this highly organized group of Molluscous animals occasions.
The branchial veins (m, m, figs. 225, 226) return, as in the lus,along the internal or unattached side of the commissure of chial laminw ; and, as they approach the temic ventricle, generally dilate into a sinus (n) on each side ; these sinuses are relatively larger in the Sepia than the Octopus. In both species the branchial vein resumes its ordinary dimen sions before terminating in the ventricle; but in the Cuttlefish the sinus is placed closer to the ventricle.