FATIGUE. 321 



to man, there is little doubt of their complete applica- 

 bility. 



It should be mentioned that some more recent 

 observations by Mann x have confirmed the changes 

 found by Hodge after prolonged exertion, and have 

 added the motor cells of the spinal cord and the 

 elements of the retina (dog) to the list of those in 

 which they occur. This author agrees with Vas, 2 

 however, in finding a preliminary swelling of the cell 

 and its nucleus after a short period of stimulation, the 

 change having been observed in both sympathetic and 

 cerebral retinal cells, and both those authors have added 

 interesting observations concerning the rearrangement 

 of the chromatic substance as the result of stimulation. 



Physiologists have been busy at the same time 

 seeking to determine how far the passage of a nerve 

 impulse along a fibre causes fatigue-changes in it. 

 Thermal and chemical changes in the nerve fibres have 

 not been clearly proven. After very prolonged stimula- 

 tion by electricity, the nerve still remains permeable to 

 impulses thus aroused. 3 Neither have definite morpholo- 

 gical changes been satisfactorily demonstrated. 4 This is 

 the more interesting, since the nerve fibre is a direct 

 prolongation of the cell body, and also since other ex- 

 periments show that the irritability and conductivity of 

 nerve fibres are not necessarily present in the same 

 degree, for a fibre may cease to be irritable, yet still 

 conduct. 



In starvation the central system is the one least 

 affected in its gross weighty and there is little doubt 

 that this weight is maintained at the expense of the 



1 Mann,y<9//r;2. of Anat. and Physio I. , 1894. 



2 Vas, Arch.f. Mikros. Anat., 1892. 



3 Bowditch, Archiv.f. Anat. and PhysioL, 1890. 



4 Edes,/6wr. of PhysioL, 1892. 



5 Voit, Zeitsch. f. Bio!., 1894. 



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