NEURITIS 147 



textural relationships and soundness ; or, in other words, 

 it is a disease of the envelopes or neurilemmar sheaths 

 surrounding the sheath of the white substance of Schwann, 

 and primarily involving the peri- and endo-neurium, the 

 tissues representing and continuous with the membranes 

 of the brain and spinal cord. 



The sheath of the white substance of Schwann and the 

 axilemma of the axis cylinder substance, being each com- 

 posed of a non-vascular layer of neuro-keratine, are 

 impervious to even the minutest capillary blood vessels, 

 and are, hence, exempt from the initial changes involved 

 in the inflammatory process, consequently we must repeat 

 that we regard neuritis, so called, as a disease primarily 

 of the non-nervous elements of the nerves or nervous 

 system. 



Its etiology must, therefore, be considered, primarily, 

 in relation to the non-nervous enveloping and supporting 

 structures of that system. As thus involving the non- 

 nervous structures, it seems to us that we must look for 

 its inception in the invasion of the intra-neurilemmar 

 spaces by a materies morbi which finds its way from the 

 cerebro-spinal cavity along the neurilemmar inter-spaces 

 by the natural movement of excretion or outflow of the 

 cerebro-spinal contained lymph ; this outflowing lymph, 

 therefore, being contaminated by chemical or other admix- 

 ture, or by the growth therein of bacterial organisms, may 

 be regarded as the most usual and important cause of the 

 primary stage of neuritis, and, consequently, as the main 

 origin and cause of what is understood as fully developed 

 neuritis. 



The invasion by disease-producing agents of the intra- 

 neurilemmar spaces of the nerves may also be accomplished 

 by the process of imbibition of the toxic agents through 

 the nerve terminals in the sweat glands wherever they 

 may be distributed on exposed areas of the skin, while 

 the manner of their transmission from these points to the 

 structures for which they have an affinity, or between 

 which and them there is a mutual affinity, is still a " moot 

 point." 



However introduced, and whatever the nature of the 

 poison, be it chemical or bacterial, the result is the same, 



