HYDROCYANIC ACID FROM BITTER CASSAVA ROOT. 
303 
though chemists have stated that the pure acid may be preserved unchanged 
if excluded from the light (which, doubtless, is true as applicable to colder 
climates), yet apparently such is not the case in the warmer portions of the 
tropics, for, even under the most favourable circumstances, it there gradually 
becomes decomposed into a carbonaceous black liquid devoid of taste and 
odour. A large quantity had recently to be condemned as useless in the 
military medical Depot at Kingston, although strictly isolated in a cool under¬ 
ground store, and excluded from light and air. 
The specific botanic differences that separate the bitter from the sweet 
cassava (Manihot Aipi, Pohl), are of such an indeterminate character, that 
botanists are inclined to class them merely as varieties of one species; the 
negroes, however, can readily distinguish them by certain peculiarities, and by 
no means can be brought to consider them as identical. 
It has been asserted that the fresh juice of the bitter cassava is equally poi¬ 
sonous with that retained under atmospheric exposure for some time. I may, 
however, express some doubts with reference to the correctness of this state¬ 
ment, for I have noticed poultry, hogs, etc., in the vicinity of Stony-hill, eat 
the roots with impunity out of the red earth, and similar facts have been 
noticed at different periods by other observers. Their exemption from death 
has been ascribed (erroneously) to the adherent red earth swallowed with this 
food, the alkaline salts of which have been supposed to neutralize the activity 
of the poisonous principle. Long, in his ‘ History of Jamaica,’ had even in 
the last century expressed views corroborative of this opinion, for he remarks 
that hogs feed on the fresh roots with avidity, and suffer no inconvenience, 
owing either to the use of the mould, or from some peculiar organic structures 
of the stomach and intestines that rendered this food capable of being assi¬ 
milated into wholesome nutriment. 
Under different conditions, however, the bitter cassava juice is far from be¬ 
ing innocuous, and, by a very natural process, becomes converted into one of 
the most deadly substances. Whenever the cortical peelings of the roots with 
the water in which they have been washed and steeped, prior to the extrac¬ 
tion of its starch, with the residual debris, have been allowed to remain exposed 
to the air for some period, and then thrown on the refuse heap adjoining the 
native huts, a gradual fermentation, or some abnormal change of its consti¬ 
tuent elements occurs, and it is transformed into a virulent poison,—hogs, 
poultry, and every animal, in fact, paying the penalty of their lives should 
they be tempted to feed off this deleterious garbage. 
This variety of cassava is cultivated in Jamaica chiefly for the large supply 
of starch it yields, deemed by the negro washerwomen to be of much better 
quality than that prepared from the roots of the sweet cassava. In the harvest 
season this starch is vended in the Kingston markets in considerable quanti¬ 
ties, and, independently of various uses, is employed to adulterate the ordi¬ 
nary arrow-root of commerce, procured from the tubers of the Maranta 
arundinacea. 
This product also constitutes an article of food among several of the negro 
tribes of western Africa, the roots having previously been roasted on the fire, 
to dissipate their noxious qualities. With some of the Susu populations to the 
northward of Sierra Leone, it is apparently more valued for the kind of spirit 
manufactured from the roasted roots. These are first moistened with water, 
exposed to the sun, and then reduced to a paste, from which the liquor is 
strained and permitted to ferment. 
Professor Bentley, who (in the absence from illness of Dr. Daniell) read the 
paper, remarked that although the present communication made no claims to 
