586 M. BIOT ON APPLYING CIRCULAR POLARIZATION TO THE 
products, which being unceasingly formed, destroyed, and renewed, are 
conveyed by the life to every part of the vegetable, and conduce to its 
nutrition. The fixed materials may be known by the analysis of the 
dead cr withered vegetable ; but even among these we have to distin- 
guish those which are essential to the existence of the plant, and those 
which have been accidentally raised from the earth by the roots, with 
the water in which they were dissolved, or held in a state of sufficient 
tenuity to be transmitted through the vessels and the vacuous spaces 
of the cellular tissue, I shall be careful not to commit myself in these 
complex questions, for which all the assistance of chemistry and of the 
microscope is scarcely sufficient, I shall confine my remarks to a few 
of the alimentary products of plants which are known to be composed 
by them, and conveyed into their various parts whilst undergoing the 
metamorphosis produced by vitality. 
My first trials upon rye were made on the 3rd of May, upon young 
shoots, in which the ear was already developed but not yet flowering, 
and indeed far from it. The roots, the stems, and the ears were sepa~ 
rately treated with water, and the extracts submitted to the tests of 
circular polarization; then these extracts concentrated but not desic- 
cated were treated with alcohol, and the substances whether precipita- 
ble or non-precipitable were in the same manner submitted to the tests 
of polarization. Finally, these substances thus isolated were brought 
into contact with yeast in order to ascertain those which were or which 
were not fermentable; after which their rotation was observed, to dis- 
cover whether it were diminished, increased, or altered in direction. 
The extract of the roots presented indications of an exceedingly fee- 
ble rotation directed towards the left. As the extract of the stems acted 
in the same direction, I thought that these feeble indications might be 
attributed to the roots not having been rigorously separated from them. 
I had not then observed that similar almost neutral mixtures may be 
produced by sugars having contrary rotation, which are detected and 
rendered discernible by fermentation when one of their elements is cane 
sugar. The experiment must be renewed and completed by the aid of 
this process the following year. 
The extract from the stems contained a mixture of grape sugar. 
turning to the left, cane sugar turning to the right; and a substance pre- 
cipitable by alcohol, which possesses the characters of gum of being 
completely soluble in water, and of directing the rotation to the left. 
These three substances originally mingled in the extract produced a 
resultant of rotation towards the left; this resultant was considerably 
weakened when the precipitable substance was separated, to the point of 
making the alcoholic extract appear almost neutral. But when the alco- 
hol was expelled by heat, and the residuum of the extract brought into 
contact with yeast, a lively fermentation took place, and developed a 
