On the Pulsations of the Molluscan Heart. 



73 



ARTICLE VII. — ON THE PULSATIONS OF THE 

 MOLLUSCAN HEART. 



By Frank C. Baker, B. S., Chicago, Illinois. 



While dissecting snails for the radula, etc., my attention 

 was attracted by the pulsations of the heart, seen through the 

 thin shell, and the thought occurred to me to study this organ 

 and record my observations. The following notes are the re- 

 sult of such study. 



Before entering upon a detailed account of the pulsations of 

 the heart, it might be well to explain the position and charac- 

 ter of the molluscan heart. For the better understanding of 

 the matter, we will divide the subject into two parts — I. Pele- 

 cypoda ; II. Gastropoda. 



I. Peeecypoda. 



The heart is an oval, transparent body and consists of a cen- 

 tral ventricle and two lateral auricles, contained in the cavity 

 of the pericardium. The ventricle gives rise to a dorsal an- 

 terior aorta and a ventral posterior aorta, which lie above and 

 below the intestine, the latter running longitudinally through 

 the ventricle. The auricles receive the blood from the bases 

 of the gills and drive it into the ventricle, from which it is 

 driven through the arteries into spaces which diminish into 

 irregular lacunae as they reach the viscera. The general 

 course of the circulation is as follows : From the ventricle the 

 blood makes its way by the large veins into a venous sinus, 

 which is a long chamber lying on the middle line of the floor 

 of the pericardium, into which it opens by a single median 

 aperture near the anterior end ; on either side of the venous 

 sinus lie the renal organs (organs of Bojanus or nephridia) ; 

 the blood passes from the venous sinus, through the glandular 

 walls of the renal organs, right and left, into the lamellae of 



(Jour. Cin. Soc. Nat. Hist., Vol. XIX, No. 2.) I Printed March 24, 1897. 



