266 
ORIGINAL COMMUNICATIONS. 
first, which he considered to possess all the characters of gum 
arabic. 
M. Caventou, in the Annates de Physique et de Chemie, 
tome xxxi, 1826, contradicts the opinion of M. Raspail, and 
is persuaded that amidon is a proximate vegetable principle, 
pure and homogeneous. 
M. Guibourt, in the same work, vol. xl, 1829, thought 
that the two parts of amidon differed more in their form than 
in their chemical nature, and under this relation he regarded 
them as constituting only one immediate vegetable principle. 
In 1829, M. Chevreul, according with the discovery of 
M. Raspail, ceased to consider amidon as one kind of proxi- 
mate principle, but he did not admit with him that the soluble 
matter was gum, since it did not possess the property of 
yielding mucic acid, and he designated the soluble part, under 
the name of amidine, and the insoluble portion by that of 
amidin. 
MM. Biot and Persoz, {Nouvelles Annates du Mu- 
seum, tome ii, 1S33,) fully admit with M. Raspail that 
amidon is composed of two bodies; considering,.however, the 
soluble portion as a pure substance, distinct from arabine, to 
which they gave the name of dextrine, by reason that a ray of po- 
larized light deviates strongly to the right in passing through a 
solid and limpid plate of this substance, or its aqueous solution. 
M. Biot states, in a note attached to the above paper, that 
to prevent all confusion, M. Persoz and himself thought it 
best to change the name of the soluble matter of fecula, after 
they had isolated it in sufficient quantities to ascertain all its 
characters, and to designate it by the property which it pos- 
sessed of turning the planes of polarization to the right, as has 
been said, stronger than any other organic substance known. 
This power or property, in substances, M. Biot called po- 
larization by rotation, and M. Fresnel, circular polariza- 
tion. 
M. Biot, in his researches on the rotatory power of various 
vegetable juices, as beet, carrot, radish, etc., ascertained that 
this property was increased by boiling the juice with the 
pulp, and he attributes it to the liberation of dextrine from the 
