474 SCIENCE PROGRESS 



Another example of the change of a plane molecular con- 

 figuration into a three-dimensional one is to be found in the 

 case of the sulphur compounds. In the alkyl sulphides having 

 the formula R — S — R', since there are only three groups, the 

 configuration must be a plane one. When alkyl iodides are 

 added to these sulphides, however, optically active substances 

 can be produced, having the formula : 



R 1 R" 



\ / 

 s 



/ \ 



R X 



and from the occurrence of optical activity it is supposed that 

 this case is analogous to that of the asymmetric carbon atom ; 

 and that the radicles R, R', R", and X are arranged at the 

 corners of a tetrahedron whose centre is occupied by the sulphur 

 atom. Of course this tetrahedral arrangement will persist even 

 if the sulphur atom be not asymmetric and no optical activity is 

 shown. Now Curci and Kunkel 1 have found that sulphine 

 bases, such as trimethyl-sulphine hydroxide (CH 3 ) 3 . S . OH, 

 have a pronounced curare-like action, which is lacking in the 

 sulphides. 



Similar results have been obtained by Bock 2 in his study of 

 the ammonia derivatives of cobalt, chromium, and rhodium, 

 which resemble each other to a certain extent. He was able to 

 show that the nature of the metallic atom in the molecule had 

 less influence upon the physiological action than was exerted by 

 the general character of the compound. 



Since in all these cases a change from a plane configuration 

 to a three-dimensional one is taking place, and since, previously, 

 we have shown how great an influence upon the physiological 

 action of certain substances is exerted by a difference in the 

 spacial arrangement of their atoms, we are not unjustified in 

 assuming that the change in configuration has some influence 

 in this case also. 



Stereochemistry is usually divided into two sections. In the 

 one division we deal with the purely static (or at least hypo- 

 thetically static) relations between atoms which give rise to 

 isomerism ; in the second section we are concerned chiefly with 



1 Curci, Archiv de pharm. et de therapy 4, 1896; Kunkel, Lehrbuch der Toxiko- 

 logie (1901). 



2 Bock, Archiv e.xp. Path. u. Pharmak.^ 52, 1, 30 (1904). 



