I 
24 SELECTED ARTICLES. 
perceived through their translucent surface, black lines, some- 
times crossing each other like the letter T, at others in the 
form of stars, as in the fecula of rye; and by turning over the 
grains by a movement communicated to the liquid, these cha- 
racters are determined not only not to be superficial, but on 
the contrary to exist in the very interior of the grain, which 
indicates an internal cellular arrangement analogous to that 
observed in the lentil;* the largest grains do not exceed 
-gL of a millimetre. From the tenacious adherence of a great 
number of these grains to each other, and the angulated sur- 
faces that they have contracted by agglutination, at the same 
time that they have preserved one of their surfaces spheroid,we 
are led to conclude that this fecula, composed of rounded 
grains, and a little soft, has been treated immediately after ex- 
traction by the heat of a stove, which heat has been somewhat 
elevated. I am confirmed in this opinion by the fact, that by 
ebullition sufficiently prolonged to distend the integuments of 
potato fecula until they have acquired twenty or thirty times 
their original diameter, the integuments of the fecula of arrow 
root attain scarcely four times the volume of the entire grain; 
which explains why Pfaff has found that ten grains of arrow 
root boiled in an ounce of water afforded only a mucilaginous 
liquid, whilst the same quantity of ordinary fecula, with the 
same quantity of water, afforded a gelatinous mass, a true 
starch. 
Fecula of Tapioca. 
(Jatropha manihot,~L.) PL fig. 7. The grains of fecula of this 
root do not exceed -f-j °f a millimetre. They assume the 
rounded form, and present in their centre a black point which 
arises from the play of light due to some circumstance in 
their internal structure, or to a depression upon their surface. 
There are two species of tapioca; that from the sweet manioc, 
and that from the bitter. It is from the root of the former 
*The fecula of the lentil (Ervurn le?is, L.) presents each grain divided 
into three or four compartments, by black curved lines, which indicate the 
presence of as many internal cells. 
