THE HEART. 



221 



tissue. In the latter part the spiral valve is wholly formed of 

 this tissue. 



Fig. 141 . 



Small group of nerve-cells from the auricular septum. Stained with picrocarmine and silver 

 nitrate, after DogieL 



E Endc'thelium (endocardium). 



G Xerve-cefla, 



M Muacle-fibrea. 



-V Xncleua. 



.V Xudeolus. 



The whole of the inner surface is lined with endothelium 



Fig. 141 b. 



IF 



C 



Isolated nerve-cells from frog's heart. I. Usual form of nerve-cell. II. Twin-cell.' 



C Capsule. 



-V Xuclena. 



.V Xncleohw. 



P Process. 



