272 WASTE AND REPAIR OF NERVOUS MATTER. 



the contrary, the supply be unduly great, or its oxidizing power artificial- 

 ly increased, there is a more energetic action. This latter condition of 

 things is presented in the earlier stages of the respiration of protoxide of 

 nitrogen, an increased muscular power, and an exaggeration of the pro- 

 cesses of intellection. The opposite state is witnessed when carbonic 

 acid, more or less dilute, is breathed, from that blunting of the intellectual 

 faculties and indisposition for muscular exertion which is felt in ill-ven- 

 tilated apartments where carbonic acid is permitted to accumulate, to the 

 profound torpor and insensibility experienced when it is in a more con- 

 centrated state. These exaltations and depressions of the capabilities of 

 the nervous instrument are, therefore, clearly of a chemical kind, and may 

 be produced artificially and at pleasure by the respiration of appropriate 

 gases or the administration of certain drugs. Nay, even the accumula- 

 tions of the effete products of the economy are sufficient to give rise to 

 such diminutions of power, as we see when bile or urea is permitted to 

 accumulate in the blood. The therapeutical and toxicological influences 

 of certain medicaments are illustrations of these principles. Of such 

 substances, some act on the sensorial and some on the motor powers, 



The copious distribution of arterial blood to the nervous centres indi- 

 Necessityofre- cates that they undergo a rapid waste. That supply can 

 pair and rest. no ^ -j^ f or ^he mere purposes of growth alone, since, when 

 once maturity is reached, the nervous mechanism presents but little ex- 

 pansion. The provision for nutrition assures us that that action must 

 be rapidly going on ; but the equilibrium of the system betrays that such 

 nutrition is not for development, but for the repair of waste ; and, in- 

 deed, this waste proceeds at such a rate that there arises in some portions 

 of this system a necessity for periodic repose, a time for the restoration 

 of the parts. If any arguments were required to establish beyond dis- 

 pute that such a disintegration of the material of the nerve centres does 

 occur, it would be furnished by an examination of the urine ; for, in nerv- 

 ous substance, phosphorus occurring as a characteristic ingredient, it 

 must give rise to the production of phosphoric acid, or salts thereof, in 

 Destruction of the supposed periods of activity. Moreover, in this meta- 

 nervous mate- morphosis of the vesicular structure ammonia must eventu- 

 portiontonerv- ally arise, from the cell walls if from no other source, and 

 ous activity, accordingly we find in the urine that characteristic double 

 salt, the phosphate of soda and ammonia. The amount of these alkaline 

 phosphates has long been known to be in proportion to the activity of 

 the nervous system, particularly in the case of individuals, such as cler- 

 gymen, whose mental powers are taxed unduly at stated intervals. The 

 general fact that the degree of energy which this system exhibits is de- 

 pendent on the activity of respiration in different tribes of life might be 

 established from many familiar instances. 



