THE SPACE RELATIONS OF ATOMS. 147 



observed in many other cases also. And in another hexa- 

 methylene derivative, inosite, which also possesses this 

 kind of asymmetry, right- and left-handed isomers have 

 been prepared. 



VH 



The inosite formerly known being inactive and in 

 divisible must have a symmetrical formula, thus : — 



OH 



Other active isomers corresponding to other asymmetric 

 formulae have yet to be discovered. 



Passing from hexamethylene derivatives to tetrahydro- 

 benzol we still find stereo-isomers (" stereomers "), corres- 

 ponding to' the formulae 



Tetrahydroterep Jit Italic acid. 

 And the isomerism continues so lonof as we have two R'R 

 attached to the ring 



Dihydrotercp lit kali c acid. 

 But just as the stereomerism of ethylene derivatives 

 disappears when they are reduced to acetylene derivatives, 

 so the stereomerism of the hydrobenzene derivatives dis- 

 appears when they are reduced to benzene derivatives. And 

 the reason is probably in both cases the same ; the atoms 

 are reduced to one plane ; again the tetrahedral construction 



