THE IDENTITY OF NEUROGLIA. 539 



in their character, which we recognize as distinctly voluntary." 

 Indeed, the nervous energy that myelin and the oxidizing sub- 

 stance procure is that which allows a frog deprived of its 

 hemispheres and its middle brain "to sink in water as though 

 the animal were of lead." 



The axis-cylinder composed of fibrils into which blood- 

 plasma penetrates being continuous with the axon of a neuron, 

 we are brought to realize the nature of the parallelism between 

 the functional phenomena of the latter and those of the supra- 

 renal glands to which we have already referred. But we must 

 not lose sight of the fact that each "medullated" nerve-fiber 

 is divided by the nodes of Ranvier into as many subdivisions, 

 and that each internodal segment receives its own supply of 

 plasma. Does the neuron receive its supply through this chain 

 of segments, or, rather, through the axis-cylinder that passes 

 through them? That the former mechanism alone prevails is 

 improbable, since so prominent a part of the entire structure 

 as its cell-body, the seat of its nucleus, would hardly be sup- 

 plied in so indirect a manner. The very importance of its 

 functions betokens the existence of direct supply. Does such 

 a vascular system exist? Fortunately, we have not far to seek. 



THE CIRCULATION OF THE NEURON. Barker, in a review 

 of the facts that have been adduced for or against the neuron 

 doctrine, 38 concludes that "it may be said, with fairness, that 

 the control instituted by hundreds of histologists in various 

 parts of the world has practically in every instance in which 

 the method of Golgi or the method of Ehrlich has been em- 

 ployed gone to confirm the conception that the neuron is a 

 unit in the sense of Waldeyer." The latter investigator's 

 words, giving the gist of his doctrine, are also quoted: "If 

 we review the main advance, made certain by the anatomical 

 investigations discussed, it lies, in my opinion, in the sharper 

 limitation, now possible, of the anatomical as well as the func- 

 tional elements of the nervous system (for such we have to 

 consider the nerve-units-neurons), and also the discovery of 

 collaterals, with their end-arborizations, by Golgi and S. 

 Ramon y Cajal." The following lines of Waldeyer's are also 



Barker: American Journal of Insanity, July, 1898. 



