iv GENERAL PHYSIOLOGY OF NEKVOUS SYSTEM 269 



phenomena of degeneration in motor cells, since their afferent 

 path remains intact. According to Schafer the explanation is that 

 after section of the axis -cylinder, its end must first undergo 

 chemical and electrical alterations, under the influence of inflam- 

 mation and cicatrisation, which keep the cell in an abnormal state 

 of protracted excitation. In fact we have seen that chromatolysis 

 accompanies exaggerated activity of the nerve. 



Chromatolysis may also result from the action of certain 

 poisons, e.g., arsenic, lead acetate, bromides, antipyrine, cocaine, 

 strychnine, alcohol, some bacterial toxines (rabies, tetanus, etc.). 



A. Monti concludes from a long series of observations that 

 chromatolysis of nerve -cells is frequent, and is definite and 

 constant in cases of disturbed metabolism. On comparing 

 preparations made by Nissl's and by Golgi's method, Monti came 

 to the conclusion that there is an almost exact correspondence 

 between chromatolysis and degeneration of the dendrites. Both 

 are observed in nutritional disturbance of the nerve -cell. This 

 correlation between the alteration of the dendrites and those 

 of the chromatophile substance agrees with Golgi's idea, that the 

 protoplasmic processes play an important part in the nutrition of 

 the nerve-cell. 



Donaggio found that while the chromatic substance is readily 

 destroyed by pathogenic causes, the intracellular reticulum offers 

 an enormous resistance. It is, on the other hand, profoundly 

 injured when the pathogenic agent is combined with the action of 

 cold. 



The subject of metabolism, or the material exchanges in the 

 nerve - centres, has only been approached, largely by indirect 

 methods, of late years. It is a priori evident that in the central 

 masses of the nervous system, as in the other tissues and organs, 

 the specific functions are intimately bound up with the successive 

 phases of katabolism and anabolism, in which the discharge or 

 accumulation of energy takes place. 



The fact that of all the tissues the central nervous system 

 offers most resistance to loss of weight in fasting shows its 

 predominance and its capacity for keeping the energy required for 

 its functions constant, by drawing its nutriment from all the 

 other tissues. This is, however, no argument for assuming that 

 the chemical work which accompanies the activity of the nerve- 

 centres is necessarily very active. 



The earliest researches on the metabolism of nerve-centres 

 was confined to establishing the variations in the chemical 

 reactions. While the white matter preserves its alkaline reaction 

 to litmus for a comparatively long time after death, the reaction 

 of the grey matter in warm-blooded animals changes so rapidly 

 that it becomes acid almost immediately after death. For some 

 time this was supposed to be the vital reaction of the grey matter 



