ARRANGEMENT OF STRUCTURAL ELEMENTS. 223 



laterally from the neuron just after its origin from the 

 cell-body, are taken into consideration the case is quite 

 altered. These branches are numerous, and probably 

 some of them become medullated, and hence within the 

 central system the idea of a one-to-one relationship 

 between cell-bodies and neurons breaks down entirely. 

 The relation, however, which Gaule sought to establish 

 was between the number of root fibres and the number 

 of medullated fibres in the cross-section of the cord. 

 The figures bearing on this would a few years hence 

 have been interpreted to mean that the medullated 

 fibres within the cord each stood for a single cell, and 

 though at present that is not warranted, it is the inter- 

 pretation of Gaule's facts, and not the facts themselves, 

 which are thereby affected. 



The many branches of the cell-body form channels by 

 which it becomes associated with other cells, hence the 

 manner in which cell elements are related by means of 

 their outgrowths is thus brought to our attention. The 

 older histologists held that the nerve cells and nerve fibres 

 of different origin were often structurally continuous, so 

 that one fibre might have similar connections with two 

 cell-bodies. Cells joined to one another by broad com- 

 missural outgrowths were often pictured, and the con- 

 ception of the nervous system was that of a very 

 extensive network, in which at least large numbers of 

 the elements, and perhaps all, were involved. According 

 to the modern view, based on embryology, a neuroblast 

 gives rise not only to the cell-body, but to all its 

 numerous prolongations. These can be followed into 

 the neighbourhood of other cell-bodies and prolonga- 

 tions, but as a rule continuity between two structural 

 units is not described. In the spinal cord of some of 

 the electric fishes (Fritsch) the cell-bodies, united by 

 broad protoplasmic bands, can be seen, but the develop- 



