Poisonous Properties of Juice of the Cassava Root.

Botanical name: 

The sweet cassava (Manihot Aipi) and the bitter cassava (M. utilissima) are very extensively grown in the West Indies and South America for their edible tubers, much used as a culinary esculent, and for the starch obtained by grating and washing, which is converted into tapioca. The milky sap of the latter species has long been known to be a strong vegetable poison, which is destroyed through pressing the grated root in the first instance, the remaining acidity being expelled by the heating process.

In 1796 Dr. Clark, of Dominica, describing the fatal effects resulting to negroes from drinking bitter cassava juice, compared the action of the poison to prussic acid, and Dr. Fennon, by experiments made at Cayenne, proved that the poison, like prussic acid, was volatile, and could be isolated by distillation.

Subsequently Messrs. Henry and Boutron-Charlard, by analyzing bitter cassava juice imported into France, ascertained that the poison was prussic acid. In 1838 Dr. Christison confirmed their discovery, by an examination of some well-preserved juice from Demerara.

Notwithstanding this early identification of the poison, no attempt had apparently been made to determine the quantity yielded by the plant untill 1877, when Mr. E. Francis, F.C.S., undertook an inquiry into the subject, the results of which be has recently published in the journal of the Royal Agricultural and Botanical Society of British Guiana.

An examination was made, not only of bitter cassava, but also of a number of samples of sweet cassava, and, contrary to expectation, the latter were found to contain nearly as much prussic acid as the former. Fifteen samples of sweet Cassava were obtained from different cultivators in Trinidad, and every one of them contained prussic acid, nine out of the number (or 60 per cent.) yielding sufficient, from 1 lb. of the root or half pint of the juice, to kill an adult. The following summary shows the average, as well as the highest and lowest quantities of prussic acid, that were met with in 15 samples of sweet, and 10 samples of bitter cassava:

Sweet Cassava (15 Samples).
Per cent. of prussic acid. Grains of prussic acid per lb.
Average, 0.0168 1.175
Highest, 0.0238 1.666
Lowest, 0.0113 0.791
Bitter Cassava (10 Samples).
Per cent. of prussic acid. Grains of prussic acid per lb.
Average, 0.0275 1.927
Highest, 0.0422 3.094
Lowest, 0.0132 0.924

The juice of the bitter cassava, mixed with molasses and fermented, has been made into an intoxicating liquor, which is much relished by the negroes and Indians. The concentrated juice, known in the colony of British Guiana as cassareep, is an Indian preparation. One of its most remarkable properties is its highly antiseptic power, preserving meat that has been boiled in it for a much longer period than can be done by any other culinary process.—Chem. and Drug., Nov. 15, 1882.

The American Journal of Pharmacy, Vol. 55, 1883, was edited by John M. Maisch.