222 Journal of Comparative Neurology. 



Two of the figures^ accompanying the text mentioned give 

 a partly diagrammatic representation of the relations of the right 

 crural and sciatic nerves as seen when the skin of the thigh is 

 removed, and the more superficial muscles are severed. 



In Figure I, drawn from a dissection of the riglit plexus 

 lumbo-sacralis of Rana virescens, we here present in some de- 

 tail, the ramifications of the crural and sciatic nerves, and show 

 the relative size of the branches, their lengths and points of 

 ramification, but not their exact anatomical relations, as the 

 branches have been severed from their muscle terminations and 

 extended in a single plane. 



1. Variations appearing in successive dissections of Rana 



virescens. 



The order of branching in the plexus lumbo-sacralis of 

 Rana virescens remains nearly constant, although the points at 

 which the branches leave the trunks are subject to some dis- 

 placement. In ten dissections, no two specimens were found 

 to be exactly alike, even when the right and left plexuses of 

 the same individual were compared. Figure I shows the con- 

 ditions which were most frequently found present. 



2. Differences between Rana virescens and the standard fur- 



nished by Rana esculenta. 



Using Table I, derived from Gaupp, as a standard, the 

 innervation of Rana virescens differs in the following particulars: 



Crural Nerve. In Rana virescens the trunk of the crural 

 nerve usually divides dichotomously. One of the resulting 

 branches, dividing into two or three coordinate branches, sup- 

 plies cutaneous areas, the second subdivides to furnish muscular 

 branches. 



In other instances the cutaneous branches are given off 

 from the trunk in two or three distinct bundles, the trunk finally 

 cleaving to furnish branches to the muscles. 



Sciatic Netve. a. In Rana virescens, the branch to the 

 plexus ischio-coccygeus (S i) has its origin from the IXth spinal 



Figures 55 and 56, Gaupp's edition, Part II, pp. 194 and 195. 



