ON NERVINE SECRETION 83 



in this and previous studies, we shall first proceed to 

 discuss the nature of what we, by a use of "scientific 

 licence," may call the intra-neural circulation. 



The intra-neural circulation, if circulation it can truth- 

 fully be claimed to be, is, like the extra-neural circulation, 

 of a duplex character, and it consists of the necessarily 

 limited movements within more or less completely closed 



FIG. 18. TERMINATION OF A NERVE IN A MUSCULAR FIBRE OF THE 

 LIZARD (Lacerta viridis). (Ranvier. ) Very highly magnified. 



ft, outer sheath of the nerve-fibre (sheath of Henle, according to Ranvier) ; b, bifur- 

 cation of the fibre ; e, node ; m, short segment beyond the node ; r, terminal 

 ramifications of the axis-cylinder ; , nuclei on the branches of the axis-cylinder ; 

 ', nuclei in the granular substance of the end-plate. The granular substance 

 lies in the intervals between the branches of the axis-cylinder ; it is not seen in 

 this figure. 



vessels of plastic, or semi-fluid, substances as represented 

 by, in the first place, the " white substance of Schwann," 

 and, in the second place, by the substance of the " axis 

 cylinder" (Figs. 8, 9). 



The intra-neural, or axonal, circulation is necessarily, 

 therefore, entirely different from the extra-neural circulation, 

 inasmuch as it consists of the movement of that substance, 

 or those substances, which may be described as truly 

 nervine within the walls of the nerve cells and the lumina 

 of the nerve fibrils, which latter are bi-tubular and may be 



