1865.] Structure and Arrangement of Ganglion Cells. 267 



separated from it by non-conducting media ; so that, as I have before men- 

 tioned, it would seem probable that the varying degrees of muscular contrac- 

 tion are induced by the varying intensity of the current transmitted along 

 a continuous nerve-fibre. 



Arguments in favour of the existence of continuous nervous circuits founded 

 upon the structure and arrangement of ganglion-cells. 



In a paper already referred to, communicated to the Royal Society in 

 1864, and published in the 'Transactions,' I endeavoured to show that 

 certain ganglion-cells which had been considered to be apolar or unipolar 

 were invariably connected with at least two nerve-fibres, and that in many 

 cases one of these fibres was coiled spirally round the other, as is well 

 shown in this drawing. These two fibres often appear as one ; but not 

 only have I succeeded in demonstrating that they are derived from different 

 parts of the same cell, but that they pursue opposite directions in the 

 nerve-trunks. I have been led to conclude that all nerve-cells give origin 

 to more than one nerve-fibre, and that these fibres, although they run 

 parallel to one another for a short distance, diverge and pursue very 

 different and indeed opposite courses ; and I endeavoured to show that the 

 arrangements I had observed received a ready explanation upon the view 

 of the existence of complete nervous circuits. 



In another communication previously referred to, published in the 

 'Proceedings' of the Royal Society for 1864, entitled "Indications of the 

 paths taken by the nerve-currents as they traverse the caudate nerve-cells," 

 I showed that there existed in the caudate nerve-cells of the spinal cord and 

 medulla oblongata a remarkable series of lines, which passed from each 

 fibre connected with the cell across the body of the cell into every other 

 fibre which diverged from it. I regarded these as indications of the paths 

 taken by the nerve-currents which traversed these cells, and my observa- 

 tions led to the inference that every single cell was the seat of decussation, 

 and therefore formed part of the course, of a vast number of different 

 nervous circuits. Upon this view of the constitution of the highly complex 

 central organs of the nervous system, it is not difficult to account for the 

 marvellous number of distinct actions effected, or of the still more wonder- 

 ful combinations of actions which must occur in the great central organs 

 of the nervous system of man and the higher animals. The axis-cylinder 

 of each dark-bordered nerve-fibre probably forms the common route along 

 which nerve-currents pass from many different parts in the nerve-centre to 

 as many different points in the periphery. Fibres prolonged from several 

 different nerve- cells seem to combine to form one dark-bordered fibre ; but 

 these and other points will be readily understood by a cursory examination 

 of the diagrams to which I now direct attention, so that it is unnecessary 

 for me to describe them minutely. 



GENERAL CONCLUSIONS. 

 To sum up briefly the results of this prolonged inquiry. The first import- 



