OLD AGE. 335 



though conducive to the general health of any portion of 

 the central system, is a source of disturbance when great 

 precision is to be attained. Leaving aside the general 

 characters of the last of the " seven ages " of human life 

 which the physicians and poets of all time have united 

 in depicting, there is one aspect of this period, so far as it 

 concerns the nervous system, which may be emphasised. 

 The conditions of this system in old age and in fatigue 

 are closely similar, though the tired cell in the prime of 

 life still possesses the power of recuperation, which in 

 old age is wanting. Even in youth extreme fatigue 

 brings with it the bodily expression of age and the 

 feeling of decrepitude, and in many ways the two con- 

 ditions thus approximate, although it is recognised that 

 fatigue depends on the exhaustion of stored material 

 and senility on the failure of the power to restore it in 

 full measure, but how the one stage passes over to the 

 other, or why, are problems still untouched. 



