CEPHALOPODA. 



541 



Fig. 226. 



Viscera of Poulp* 



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,fg. 225) are 

 appended to the roots of the gills : in the Octo- 

 poda they are simple pyriform muscular cavities 

 (k, k,fg. 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, 

 ^g. 225,) 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 



* From Mayer, Analecteu fur Vergleichende 

 Anatomic, tab. v. 



and decussating carneae 

 columntE ( k,fg. 226), 

 and where they com- 

 municate with the ve- 

 nous sinus two semi- 

 lunar valves (I) are 

 placed to prevent re- 

 gurgitation . Their func- 

 tion is to accelerate 

 the circulation through 

 the branchiae ; 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,fgs. 225, 226) 

 return, as in the Nauti- 

 lus,along the internal or 

 unattached side of the 

 commissure of thebran- 

 chial laminae ; and, as 

 they approach the sys- 

 temic ventricle, generally dilate into a sinus (n) 



Fig. 227. 



Systemic Ventricle, Onychoteuthis. 



