BY JAMES M. PETRIE. 861 



podes. The possible existence of three dextro- and three Ifcvo- 

 inethyl esters is thus deteimined. It now remains to ascertain 

 (a) whether tlie few inositol esters wiiicli have been is(jlated up 

 to the present time, represent the same stereo-isonier, (6) whether 

 the compound obtained h'om Ifeterodendroii is identical with any 

 of the others, t)r represents the second or third isomer. 



Occurrence in iiafure. — It has been previously stated that 

 theoretically there can exist ten stereo-isomeric forms of inositol 

 as a maximum possible number: — - 



7 inactive by internal compensation (meso), 



2 active, dextro and Ipevo, 



1 inactive, racemic or dl, 



10 isomeric forms. 



Only the inactive inositols have yet been found existing in the 

 free state in nature, but esters of both active and inactive 

 inositols are found. 



{a) Inactive inositol. — This form, widely distributed in animal 

 tissues, and already well known to physiologists, possesses the 

 formula of one or other of the seven internally compensated 

 molecules, and it is worthy of note that this is the only form 

 found in the animal kingdom. It has always been referred to in 

 physiological chemistry as one substance, with definite and con- 

 stant general properties. But no one so far has troubled to ex- 

 amine minutely, material from widely different sources or organs, 

 as to the particular properties which would differentiate these 

 inactive isomers, such as crystallographic measurements, or optical 

 properties. 



It was discovered in animals, in 1850, by Scherer, in extracts 

 of flesh,* and in plants, six years later, by Vohl.f This author 

 was examining the sap of unripe pods of Fhaseolus vulgaris, and 

 after completely fermenting the sugars, and distilling off the 

 alcohol, he found that the solution still possessed a very sweet 

 taste. He then separated a manna-like substance, 



* Liebig's Annalen der Chemie und Pharni., Ixxiii. 

 t Ibid., xcix., 1856, 125. 



