1922] ATWOOD—FORM ALDEHYDE 243 
experiment was tried of giving to each tube at the end of the test 
anumber value. No digestion (as in the tubes lacking diastase) was 
indicated by 10, complete digestion (no starch) by o, and inter- 
mediate shades proportionately in between. It is not claimed that 
this method equals the accuracy of colorimetric technique, yet the 
differences were so pronounced that on checking over results with 
NO 
DIASTASE 
FORMALDEHYDE EFFECT 
ON 
DIASTASE 
at 1000 400 420 I il 0 40 620 j 9 BO 
c CHECK 
Fic. 6.—Effect of varying concentrations of formaldehyde on starch digestion: 
height of lines indicates amount of starch remaining undigested (all conditions shown 
in duplicate); 1 cc. 0.5 per cent solution Merck’s diastase, 10 cc. 25 per cent soluble 
starch solution, and 4 cc. of varying concentrations of formaldehyde used in all but 
controls. 
other observers who were unfamiliar with the conditions presented, 
it was thought that the situation did not justify the other method. 
Referring to fig. 6, in which these values are presented graphically, 
it will be observed that with the higher concentrations of formalde- 
hyde the digestion is not greater in amount than that occurring in 
the check containing no diastase. Commencing with the concentra- 
tion of 1-20 of formaldehyde, and running from that point down to 
