110 ELECTRO-PHYSIOLOGY CHAP. 



to the structure of the nerve -fibres. The sole functional, 

 chemical alteration of nerve which, if not undisputed, is still 

 maintained on experimental grounds, is its reaction. Immediately 

 after du Bois-Keymond had established the functional alteration 

 of the reaction in muscle, Funke (67) made a corresponding 

 statement for medullated nerve, finding the cross-section both of 

 peripheral nerve- trunks and of the more easily tested spinal cord 

 of the curarised rabbit and frog to be neutral, while at a certain 

 time after death, or in strychnin poisoning, they gave an acid 

 reaction. Both assertions were disputed by Heidenhain (67), and 

 confirmed by Eanke (67). According to Gescheidlen and Edinger 

 (67), the gray matter of cord and brain is acid even in the fresh 

 state, the white matter being neutral : Moleschott and Battistini 

 invariably find the former more strongly acid than the latter, both 

 during rest and during strong excitation. In direct contradiction 

 of this, Langendorff (67) affirms that the central nervous system 

 of the frog as a whole gives an alkaline reaction, and that the 

 same is true of the living cerebral cortex of the rabbit or guinea- 

 pig. Both in asphyxia and in anaemia, however, the reaction 

 quickly becomes acid. The obvious contrariety of these statements 

 is in large measure owing to the fact that the chief subject of 

 experiment has been the excessively unstable ganglionic substance 

 of the nerve-centres, the reaction of which alters with extreme 

 rapidity. Pfliiger, in fact, after even the most rapid washing-out 

 of the brain with ice-cold physiological saline, observed an 

 immediate post-mortem acidity of the gray matter. In view of the 

 complete similarity of vital conditions in nerve-cells and fibres, it 

 can hardly be found surprising that the metabolism of these two 

 most essential structural elements of the nervous system should 

 differ completely. In no case can the conclusions as to ganglionic 

 parts be taken to gauge the reaction of nerve-fibres. Moreover, 

 it is hardly to the purpose to take (as has usually been the case) 

 a medullated nerve as the test of a final reactionary alteration, 

 since only the substance of the axis-cylinder in these fibres can 

 be counted as the essential physiological constituent. It is quite 

 possible that the medullary sheath (which bears little direct part 

 in the excitatory and conducting processes) may mask a real 

 alteration of reaction at the cross-section. 



As little as chemical alterations of the nerve-fibre have been 

 established during, and in consequence of, excitation, can the ther- 



