Osazone Method for Detecting Sugars. 45 
absorbed, is probably one of very great rapidity, the movement of 
such substances is always controlled by the laws of diffusion. 
Mangham, however, speaks of an “ adsorptive suction" 
With regard to Mangham’s “ wave ” concept, I must confess to 
having experienced some difficulty in arriving at a point of view from 
which this mental picture is comprehensible. It appears to have had 
its origin in the application of a false analogy. Mangham states that 
“a wave of disturbance and readjustment of equilibrium is propagated, 
in much the same way as the firing of shells from a battery leads 
to the depletion of the immediate supply, followed by a replenishing 
from the reserves, etc., and ultimately from the factory, so that the 
scheduled relations are maintained between the various stores at 
intermediate points.” It is clear that in this picture, which involves 
the intervention of human activity in the replenishing of reserve 
dumps successively from the rear, the conception of a wave is not 
altogether inapplicable. Nevertheless, if the shells represent sugar 
molecules and the dumping spots absorbing particles, its use as an 
analogy is entirely false and misleading. It obviously involves a 
diffusion of sugar against the diffusion gradient. 
FRANKLIN KIDD. 
St. John’s College, Cambridge. 
THE OSAZONE METHOD FOR DETECTING SUGARS 
IN PLANT TISSUES. 
I N a recent number of this journal, S. Mangham offers some 
explanations of his earlier writings on the osazone method for 
detecting sugars in plant tissues. In the course of his note he calls 
attention to a passing reference made by us in regard to the detection 
of sugars in which we said “ The fact that Mangham should claim 
to distinguish between ^/-glucose and ^-fructose in the plant by the 
osazone test, when their phenyl osazones are of course identical, is 
not very reassuring as to the degree of reliability of his results.” 
Mangham is in error in reading into this statement an assump¬ 
tion that he considers a chemical difference to exist between the 
phenyl osazones yielded by glucose and fructose. These sugars 
yield the same phenyl osazone. Many chemists feel sceptical of 
microchemical tests applied to plant tissue and would only fall 
