ON THE NEURONS, GENERALLY 331 



ing, and conveying, the needful nourishment for their 

 maintenance, and insulating them from contact with the 

 surrounding neuroglial structures, and capillary blood- 

 vessel mechanism. 



Being thus protected, insulated, and nourished, the 

 nuclei, with their contained nucleoli, become subservient 

 to, and perform the functions of producing, receiving, 

 conserving, and distributing, of nerve force, the former, 

 the nucleus with its continuation, the axis-cylinder, acting 

 the part of conveyancer, the other parts of this compli- 

 cated work being performed by the latter, the nucleolus, 

 the only " independent " structure, in the hierarchy of the 

 higher nerve elements, or bodies. 



The axis-cylinder of the nerve fibrils, may be regarded 

 as continuous with the intra-nuclear substance, in its 

 inmost, or most intimate, molecular aspect, and the 

 " white substance of Schwann," or medullary substance, 

 as continuous with the contents of the cell body proper. 

 The nucleoli must, thus, transmit, or convey, their con- 

 tained, and produced, energy, directly into the substance 

 of the axis cylinder of the fibrils, while the " white sub- 

 stance of Schwann," encased in its primitive sheath, and 

 lined by the axilemma, performs the functions of, insula- 

 tion, and protection. 



The various structural elements of the neuron, are 

 formed, or secreted, and circulated, although in a very 

 different manner from the cerebro-spinal fluid, and are 

 excreted, or exuded, in a likewise very different manner, 

 the semi -solid, or plastic, materials, constituting, the 

 " white substance of Schwann," and the axis cylinders, 

 suffering an organised excretion, so to speak, in the 

 form of epidermic scales, and appendages, epi- and endo- 

 thelial cells, and scales, and the sarcous elements of 

 muscle fibres. The quantity of material, thus removed 

 from the body, must be regarded as largely, if not 

 entirely, due to nerve fibre growth, and circulative dis- 

 integration, and elimination, but of course impossible of 

 measurement by any known means roughly speaking, 

 however, we may regard the rate of shedding, of epidermic, 

 and epithelial, scales, and the growth of hair, and nails, 

 with the maintenance of muscular fibre, generally, as, to 



