420 MONTGOMERY. [Vol. XIII. 



V. Dotted Substance of the Fibrous Core. 



The fibrous core (Figs. 25, 30, 35 a-c, 40, F. C.) of the brain 

 and lateral chords is composed of the so-called "dotted sub- 

 stance " (" Punktsubstanz " of Leydig), and is divided from the 

 outer ganglion-cell layer by the inner neurilemma (i. Neur). 

 The only cells occurring within the fibrous core are the branched 

 cells {Ngl. C.) of the inner neuroglia tissue, and these are sit- 

 uated mostly peripherally, just beneath the inner neurilemma, 

 though a small number penetrate also into the dotted substance. 



The fibrous core is composed of: (i) fibres of the cells of 

 the inner neuroglia, which compose its greater part, (2) nerve 

 tubules and their sheaths, (3) irregular spaces containing body 

 fluid. Apparently no fibres or strands of the inner neurilemma 

 penetrate for any considerable distance into it. It cannot be 

 too strongly emphasized, that in order to arrive at a clear under- 

 standing of this much-discussed portion of the central nervous 

 system, comparisons must be made between preparations fixed 

 in different fluids (especially Hermann's fluid and sublimate 

 solutions), and between those differentiated by different stains. 

 Since the structure of the fibrous core differs somewhat in 

 Lmeus and Cerebratulus, it may be described separately for 

 these two genera. 



A. Linens. 



In this genus there is a proportionately larger number of 

 inner neuroglia cells around the fibrous core than in Cerebratulus, 

 and their fibres are also coarser and hence more easily followed. 

 These fibres, as well as the cell bodies, are of a dense, granular 

 structure, and stain intensely with eosin; and though they 

 branch excessively, I have never found anastomoses between 

 the fibres of adjacent cells. ^ The fibres of the peripheral inner 

 neuroglia cells radiate into the fibrous core, producing the 

 fibrillar, staining substance of the latter. A single neuroglia 

 fibre with its branches may often be traced for a considerable 



1 If it were necessary to be precise in our terminology, the term Jibre could be 

 restricted to the branch of the cell, 2.-ndL fibril employed for secondary branches of 

 these fibres ; but these distinctions are of doubtful value, and need not be employed 

 here. 



