CIRCULATION IN CEPHALOPODA. 



207 



extract from that fluid ; or, on the contrary, they may be 

 emunctories, by means of which the blood is purged of 

 some noxious principle. This last conjecture, he thinks, 



Fig. 39. 



is rendered more probable by the abundance of the yellowish 

 mucus poured out ; and it is certain that the communica- 

 tion between the interior of these bodies and the medium 

 in which the animals live, is very open ; for when air or an 

 injection is thrown into the vein, the air or the injection 

 passes very readily through the glands into the venous 

 cavity, and thence outwards ; or, on the contrary, if air is 

 blown by its external orifice into this cavity, it passes 

 thence very often into the veins.* "Were it practicable," 

 says Dr. Fleming, " to analyse the yellow mucus which 

 these glands contain, some light might be thrown on the 

 subject : indeed, it appears not improbable that this arrange- 

 ment is analogous in its functions to the urinary system in 

 the most perfect classes." "j- 



You will remark, that every use herein attributed to this 

 apparatus is entirely conjectural, and although the following, 

 thrown out by Mr. Owen, is of the same character, yet it 

 is distinguished by a greater ingenuity and likelihood. He 

 says, " In all the Cephalopods the follicles are appended 

 to that part of the vascular system which terminates the 

 greater, or commences the lesser circulation. But besides 

 their use as connected with the respiratory system, and 

 effecting changes in the blood itself, either by way of depu- 

 ration or addition, I am induced to believe, from the follow- 

 ing considerations, that they also perform a secondary func- 

 tion which has not hitherto been attributed to them. 



* Mem. sur les Mollusques, i, 18, 19. 



t Phil. Zool. ii. 426. 



