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 or withered vegetable ; but even among these we have to distin- 

 guish those «'hich 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 

 tenuitj' to be transmitted through the vessels and the vacuous spaces 

 of the cellular tissue, I shall be careful not to commit mj'self 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 %vhich are known to be composed 

 by them, and conveyed into their various parts whilst undergoing the 

 metamorphosis produced by vitality. 



My fii-st 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 cars 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 fennentable ; 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 sugai's 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 bj heat, and the residuum of the extract brought into 

 contact with yeast, a lively fermentation took place, and developed a 



