EXTRACT XXX. A. 



ON THE NEURONS, GENERALLY. 



THE central or systemic nervous system, growing out 

 of, and supported by, the neuroglia, may be regarded 

 as, a congeries of neurons, and each neuron may be 

 regarded as consisting of a cell, with its contained nucleus, 

 and nucleolus, the cell, by its wall, and contents, being 

 continuous with the " white substance of Schwann," and 

 its containing sheath, the nucleus, by its wall, and con- 

 tents, being continuous with the axis cylinder, and its 

 containing sheath, while the nucleolus rests within these, 

 as an independent body, to which, we are of opinion, 

 the sensory nerve impulses are conveyed, and in which, 

 if unexhausted, they may be retained, or converted into 

 motor impulses, and discharged; or where, on the other 

 hand, if the impulses, or molecular nerve force move- 

 ments, be highly specialised, as when they come direct 

 from the senses, they may remain stored up, and available 

 for future psychic use, as are, the negatives of the 

 photographer, or as electric power in, Leyden jars, or 

 the " accumulators " of the electric engineer. 



O 



The highest types of these neurons may be looked for 

 in the cerebral cortex, and here the individual cells 

 may be seen, taking root in, and from, the neuroglia, 

 by apical, and collateral, dendrites, dendritic processes, 

 or dendrons these processes, more especially the apical, 

 terminating in free radical extensions, from which,- in 

 turn, bud-like processes, or gemmules, project into the 

 surrounding neuroglial substance, apparently, in a manner 

 analogous to the rootlets of a plant, where they imbibe 



