THE PHYSICAL LAW OF MATTER 165 



basal, organised texture, and is extracted from that 

 situation by the dendrons of the nerve cells, or neurons, 

 and conveyed to the substance of the nerve structures 

 proper of these neurons, viz. to the cell body with its 

 proper plasmic contents, the nucleus with its special 

 contents, and the innermost neuronal structure, and the 

 nucleolus with its most special contents. The nerve cell 

 contents and the nuclear substance being continuous, 

 respectively, with the white substance of Schwann, and 

 the axis cylinder substance of the nerve fibre, initiate 

 and continue other two circulations, represented by these 

 two substances, along each axonal process, or axon ; the 

 two substances being fluid, or plastic, enough, to allow 

 of more or less freedom of onward movement, or 

 circulation. 



These two central circulations are carried on through, 



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or along, continuous sheaths, or cases, enclosed in a 

 neurilemma composed of layer after layer of dense 

 fibrous tissue containing, within well-defined limits, 

 inter-spaces occupied by cerebro-spinal, or neural, lymph, 

 as distinguished from haemal lymph. These inter- 

 neurilemmar spaces, with their neural lymph contents, 

 represent at least other two circulations, continuous with, 

 and from, the sub-arachnoid and sub-dural spaces, respec- 

 tively. Thus, along every afferent, and efferent, nerve 

 fibre, from its origin to its terminal distribution, we have 

 a series of at least four separate and individual circu- 

 lations simultaneously in operation and requiring for 

 their maintenance an unbroken continuity of tubes and 

 an unfailing supply of fluids, and colloid materials, of 

 appropriate consistence, and physiological quality. An 

 axonal nerve fibre is, thus, a compound of at least four 

 tubes circulating fluids and substances of different 

 consistence, and qualities, along its intra-spaces, each 

 circulation differing from the other according to the 

 consistence of its material and the freedom from 

 obstacles to its onward progress, the two inner being 

 necessarily slow, but the two outer necessarily relatively 

 quick. 



The circulations here outlined are carried on mainly 

 towards a free terminal surface, with the exception of 



