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O. F. BLACK 
which were of sharp monoclinic form and largely admixed with needle- 
like crystals quite similar to natural raphides and of approximately 
the same size. To observe the effect of this preparation on the mouth, 
the crystals were filtered, washed with water, dried, and then incor- 
porated in melted paraffin. When the gum thus produced was masti- 
cated for a short while it left in the mouth a burning sensation com- 
parable to that experienced from dasheen leaves, though less intense. 
An endeavor to isolate the naturally-formed raphides was only 
partially successful, but the attempt served to bring out further evi- 
dence that the raphides are responsible for the acrid taste. Corms 
of the Indian turnip {Arisaema triphyllum (L.) Torr.) were used in this 
experiment, since they are easily obtained in the vicinity of Washing- 
ton, contain raphides in large quantities, and have an intensely acrid 
flavor. The turnip-like corms were peeled, washed, and grated to a 
pulp which was supended in distilled water for some time to allow the 
needle crystals to work out of the cells. The mixture was then filtered 
by suction through a rather coarse cloth, stirred up again with water 
and again filtered. A drop of filtrate, under the microscope, showed 
the presence of many needle crystals mixed with some starch granules. 
The filtrate was next centrifuged, the supernatant liquid poured off, 
the residue stirred up with distilled water and again centrifuged, 
this process being carried through several times until the mixed raphides 
and starch had been well washed. The solid residue from these opera- 
tions had an intensely acrid flavor, differing in no respect from that of 
the untreated tuber. 
An endeavor was made to obtain the raphides in a still purer form 
by eliminating the starch through the action of diastase. The washed 
mixture of starch and raphides was subjected to the action of yeast 
over night at a temperature of 40° C. When the preparation was 
examined the following morning, however, no raphides were found in it, 
and, moreover, it had lost entirely its acrid taste. This experiment, 
therefore, while it failed of its original object, nevertheless offers 
strong additional proof that raphides are the cause of acridity. 
In repeating the above described experiment on the dasheen, 
similar observations were made. 
Conclusions 
All experimental evidence goes to show that calcium oxalate crys- 
tals are the sole cause of the acrid taste of the dasheen by the mechani- 
cal irritation of the mucous membrane of the mouth. 
