122 PKOCEEDINGS OF THE SCIENTIFIC ASSOCIATION. 
Dr. Christison in his treatise on poisons has the following : 
44 The janipha manihot or cassava plant has two varieties, 
one of which produces a small spindle-shaped bland root, 
called in the West Indies sweet cassava, while the other has 
a much larger, bitter, poisonous root, called bitter cassava.” 
Dr. Taylor states that 44 the root of one variety of this 
West Indian plant, known under the name of bitter cassava, 
contains in its juice prussic acid.” 
Dr. Hamilton, for many years resident in the West 
Indies, in one of an interesting series of articles on West 
Indian medicinal plants, which he contributed to the earlier 
numbers of the Pharmaceutical Journal , writing of sweet 
cassava, says ( Pharrn . Journ ., vol. v., p. 81) : — 44 The janipha 
Icefflingii so closely resembles the former (bitter cassava) in 
its external characters, that it can hardly be distinguished 
with certainty by even an experienced eye, and has been 
considered by Browne and many other writers merely as a 
variety. Its root, however,' is wholly destitute of the active 
principle which renders the bitter cassava in its unprepared 
state an object of such just apprehension ; the roots of the 
sweet cassava requiring no other preparation than simply 
boiling or roasting, and even admitting of being eaten raw 
with impunity.” 
The above extracts are sufficient to show that the distinction 
hitherto made between bitter and sweet cassava depends 
far less upon external characteristics than upon the assumed 
presence or absence of the noxious principle which we now 
know to be prussic acid/ That a certain variation is ex- 
hibited in the mode of growth of cassava is a well-known 
fact, but the preceding experiments prove that the presence 
of the noxious principle is not confined to one kind of the 
