1S9S] RUDIMENTARY NERVOUS SYSTEM 337 



face superieure devient a son tour electro-negative et reste ainsi 

 pendant quelqne temps." l 



10. Excitants work either by disorganising- the nervous textures 

 or by a subtraction of water, that is, either by mechanical acts of 

 disassociation or else by a modification in the density of the axis- 

 band, or even of the neuroplasma itself. The influence exercised by 

 interstitial water on the excitability of nerves appears to be quite 

 evident, the mere fact of a nerve's desiccation rendering it inexcit- 

 able, though it is susceptible of recovering its physical and physio- 

 logical properties when it has retaken by imbibition the quantity of 

 water necessary for the discharge of its functions. Morphia may 

 perhaps work by modifying the state of hydration of the neuro- 

 plasm. It is likewise possible that the blood's circulation and its 

 state of concentration have an indirect influence on the velocity of 

 nervous transmission. (Experimental studies of Mosso.) 



11. Most acids work as excitants if applied to nerves. This 

 point being settled, I can further state that a similar result is to be 

 obtained by applying to the point of an artificial nerve of mercury 

 and lead a little chromic or azotic acid, either concentrated or 

 diluted. This also produces : («) Contraction and tumultuous 

 movements, (b) Production of waves, by discharge of nitrogen 

 dioxide. This is certainly one of the most weighty demonstrations 

 of my theory. 



The neuroplasm, the axis-band in general, ought to vibrate 

 under the influence of* acids, because the chemical action practised 

 by the latter on albuminous matters must originate the shocks and 

 vibrations attendant on the subtraction of water, discharge of carbon 

 dioxide, etc. 



It is needless to observe that the movements of the artificial 

 nerve of mercury and lead can be explained by the action of gas 

 when the chromic acid is applied. The bioxide of nitrogen slowly 

 issuing from the bottom of some drops of nitric acid (1 in 10 of 

 water), placed on the surface of the metal, begins to whirl round, 

 after the manner of infusoria, or to produce some amoeboid move- 

 ments that are extremely curious. 2 



12. Physiologists are all of opinion that bile is one of the 

 nerve's excitants. 



In certain parts of the nervous system the continual vibrations 

 observed may be due to the excitant action of oxygenated blood, by 

 a discharge of carbon dioxide. 



13. Rough excitations have the power of effecting the nerve's 

 vibrations, while slow and gradual excitations are unable, in spite of 



1 Revue Scicntifiquc, Juillet a Decembre 1S82, p. 735. 



2 Note the amoeboid movements that Biitschli observed in foams and Pn'aubert in 

 globular rays. "La vie mode de mouvement." Paris, 1898. 



2 A 



