1888.] 



On the Electric Organ of Raia circularis. 



213 



least of the inhibitory fibres of the vagus go, there to come into 

 intimate relation with the cardiac mechanism. 



Effect of Stimulation of Ostial Parts of Great Veins in certain Abnormal 



Conditions. 



At certain stages of the process of asphyxia, and in the dying heart, 

 there is often seen a very remarkable alteration in the behaviour of 

 the ostial parts of the great veins towards direct stimulation with 

 interrupted currents. In such circumstances, an inhibition of the 

 spontaneous rhythmic action of these parts may often be seen as a 

 result of direct stimulation, whereas in the normal state such a stimu- 

 lation is productive of immediate and striking acceleration. 



VI. " On the Structure of the Electric Organ of Raia circularis." 

 By J. C. Ewart, M.D., Regius Professor of Natural History, 

 University of Edinburgh. Communicated by Professor J. 

 Buedon Sanderson, F.R.S. Received April 30, 1888. 



(Abstract.) 



This paper gives an account of the structure of the cup-shaped 

 bodies, which, as mentioned in a previous paper read 26th April, 

 1888, make up the electric organs of certain members of the skate 

 family. The structure of these electric cups has been already 

 studied in three species of skate, viz. : Raia fullonia, R. radiata, 

 and R. circularis. The present paper only deals with the electric 

 organ of R. circularis. It shows that the cups in this species 

 are large, well-defined bodies, each resembling somewhat the cup of 

 the familiar "cup and ball." The cup proper, like the disks of 

 R. batis, consists of three distinct layers, (1) the lining, which is 

 almost identical with the electric plate of R. batis ; (2) a thick 

 median striated layer ; and (3) an outer or cortical layer. The lining 

 or electric plate is inseparably connected with the terminal branches 

 of the numerous nerve-fibres, which, entering by the wide mouth in 

 front, all but fill the entire cavity of the cup, and ramify over its 

 inner surface, the intervening spaces being occupied by gelatinous 

 tissue. This electric layer, which is richly nucleated, presents nearly 

 as large a surface for the terminations of the electric nerves as the 

 electric plate which covers the disk in R. batis and R. clavata. The 

 striated layer, as in R. batis, consists of numerous lamella?, which 

 have an extremely contorted appearance, but it differs from the cor- 

 responding layer in R. batis, in retaining a few corpuscles. The 

 cortical layer very decidedly differs in appearance from the alveolar 

 layer in R. batis. It is of considerable thickness, contains large nuclei, 



Q 2 



