336 HOW TO WORK 



and even this leaves many points worthy of more extended investiga- 

 tion unsettled. 



The fine fibres resulting from the subdivision of the dark -bordered 

 fibres soon divide into numerous branches, which form a highly 

 complex plexus, the subdivisions of which are connected here and 

 there with numerous nuclei, as represented in the upper part of the 

 papilla, fig. 389. It is impossible to follow these, but in fig. 391 is 

 a diagram representing the probable arrangement. Each papilla 

 seems to be connected with the nerve centre by special fibres and 

 with neighbouring papillas by commissural .fibres, fig. 403, pi. LXVI. 

 This arrangement, familiar to anatomists in the optic commissure, 

 exists here and in all other nerve organs, pi. LXIII, fig. 394. 

 The general arrangement of the vessels, muscular fibres, and other 

 tissues, will be understood if the drawings in pi. LXIII be carefully 

 studied. 



392. Of the Cells of Nerve Centres, Caudate Nerve Cells. The 

 caudate nerve cells, of the spinal cord and brain have long been 

 objects of attentive study. They are without doubt intimately 

 concerned in the production of the highest nerve phenomena. The 

 structure of these cells is very peculiar. Certain granules, lines, and 

 inequalities in their substance, particularly upon the surface, have 

 long been familiar to observers; but in 1864 I found some cells 

 in which the arrangement of lines at different depths was very 

 distinct. These lines could be traced, as is well represented in 

 fig. 395, and shown diagrammatically in fig. 396. They clearly passed 

 from each of the fibres across the cell into every other fibre proceed- 

 ing from it. I could not but conclude that these lines marked the 



O 



paths taken by the different nerve currents which traversed the 

 cell. 



The fibres proceeding from the cell consist of the same material 

 as that of which the cell itself is composed, and are, as it were, 

 drawn off from it. 



Fine fibres resulting from subdivisions of the larger fibres leaving 

 the cell, unite together to form single fibres, as represented in 

 fig. 397. Thus is formed a dark-bordered nerve fibre. Every one 

 of these fibres again divides and subdivides as it approaches its 

 peripheral distribution. The manner in which this occurs will be 

 understood by reference to figs. 399, 401, 402, pis. LXV and LXVI. 

 See also figs. 193, 194, pi. XXX. 



393. Of Spherical and Oval Nerve Cells. In the ganglia con- 

 nected with the sympathetic nerves of the abdominal and thoracic 

 cavities, in those on the posterior roots of the nerves, in the ganglia 

 connected with the nerves of the heart and of many of the vessels of the 



