PHYSIOLOGY OF THE INVERTEBRATE HEART. 145 



lion. The nerve takes a posterior direction along the cephalic 

 aorta for a distance of about 3.5 cm., when it divides in two, one 

 branch continuing in the posterior direction along the posterior 

 aorta to the liver and the intestines, the other turning dorsally 

 towards the kidney. Here the nerve bifurcates, both branches 

 entering the kidney at its ventral side, a little to the right of the 

 exit of the aorta through that organ. By aid of a strong dis- 

 secting lens a filament from one of these renal nerves can be fol- 

 lowed on to the ventriculo-aortic junction. I was not able to 

 trace any nerve branch to the auricle, although stimulation of the 

 visceral nerve shows that nerve fibers enter the heart of this slug 

 both at the aortic and the auricular ends. The dissection reveals 

 no ganglion at the point on the visceral nerve where the reno- 

 cardiac nerve is given off, corresponding to that in Liina.v. 



The nervous system of Helix (PI. VII., Fig. 19) resembles that 

 of the slugs very closely. The pallial ganglion gives rise to four 

 nerves, the lateral pair (1,4) entering the pallial complex and 

 the mantle. The right member of the median pair (2) goes to 

 the pallial complex, but it cannot be traced to the auricle or the 

 kidney, and stimulation of the nerve does not affect the heart. 

 The left member (3) of the median pair is the visceral nerve 

 proper. On its posterior course it gives off a branch to the cop- 

 ulatory organs (5), and a little further posterior another small 

 branch which probably enters the lung (6). At the point of 

 origin of this branch there is a slight ganglionic swelling on the 

 nerve. At the level of the ventricle the nerve bifurcates, one 

 branch continuing in the posterior direction into the reproductive 

 gland (9). The other branch (7) turns to the right and before 

 entering the kidney gives off a filament (8) which takes a pos- 

 terior direction, probably reaching the stomach and the intestine. 

 The nerve can be followed into the kidney without any difficulty, 

 but I was not able to trace any of its branches through the kid- 

 ney and into the auricle, as Ransom has described and figured 

 it, although I have physiological evidence that such connection 

 is made. Before the nerve enters the kidney a small filament is 

 given off to the aorta and the pericardium, but I could not trace 

 it on to the ventricular musculature, although the physiological 

 evidence is conclusive that nerve fibers enter the ventricle at the 

 aortic end. 



