Letter from [W A Herdman] of the University of Liverpool to William B Hardy Makes some points about Hardy's question on the effect of diet on mental activity. Notes that brain work 'makes one just as hungry' as physical -- that the same methods cannot apply to determining muscular and mental activity -- that it is unscientific to propose 'something from nothing' -- wonders if there is some chemical measurement of mental activity that gives results a calorimeter cannot. 4 May 1917