SCLEROSIS OF THE NERVOUS SYSTEM 153 



ing ; the two conditions respectively representing, as it 

 were, the positive and negative aspects of the intra-neural 

 disposal of the white substance of Schwann, and generally, 

 or at least in sclerosis, that of the axis cylinders. 



These sclerosed sheathings, with the remains of their 

 former contents altered by pathological changes, together 

 with their encircling endo- and peri-neural coverings, com- 

 prise, therefore, the only vestigial remains left by the arrest 

 of the intra-neural circulation, and constitute but the pas- 

 sive or inert structural survivals of once functionally active 

 mechanisms and most highly endowed material organisms 

 dead, yet alive! They are dead so far as the systemic 

 nervous system is concerned, from which their separation 

 is permanent, but alive in virtue of their supply of sympa- 

 thetic nerve energy and the retained power of the restricted 

 nutrition and metabolism possessed in common by all 

 so-called non-nervous or sympathetically innervated struc- 

 tures. 



Sclerosis, moreover, befalls other structures, more 

 especially of the muscular character, but also of the 

 cellule-fibrous varieties, and points to the incidence of 

 involutionary change, comprising that of failing nutrition > 

 lapse of function, and textural retrogression, with accom- 

 panying and consequent structural and functional failure 

 and breakdown, such as is seen in premature senility, 

 where the arterial structures are peculiarly liable to partici- 

 pate, and show that the initial stage of involution has 

 begun, and that, generally speaking, it inexorably continues 

 until the process is complete and the continuance of life 

 impossible. 



There are those who think that we should always look 

 here for the earliest symptoms of sclerosis, and if means 

 of preventing the threatening breakdown can be devised, 

 the greatest chance of their doing good is secured at this 

 stage, or before structural degenerative change has fairly 

 set in, i.e. before neuro-muscular nutritive failure and 

 shortage of neuro-muscular dynamic supply have become 

 established realities. 



In relation to incidence, this affection seems to fall 

 entirely, as we have said, on structures innervated by the 

 systemic nervous system, i.e. the musculo-osseo'us struc- 



