— 132 — 

 COOH COOH COOH 



CH 3V /CH-COH(CH 3 ) /CH-C(CH 3 ) /C = C (CH,) 



>C I >CH 2 >C a %CH >C 8 >CH 2 



CH/ \ ' CH/ \ CH/ \ 



3 X CH 2 -CH 2 3 X CH 2 -CH 2 X CH 2 -CH 2 



This behaviour explains that on the one hand the dibasic acid 

 cannot be converted into the cyclic isomeride, and on the other, 

 that in the cyclic isomerides an oxidation of the CH 3 -group does not 

 take place in the organism. 



If the cyclic camphors cyclocitral and cyclogeraniol are compared 

 from a physiological point of view with the aliphatic isomerides, 

 it is conformably found that the latter have a more powerful action 

 than the cyclic isomerides 1 ); a remarkable contrast therefore shows 

 itself here to the behaviour of the previously discussed cyclic and 

 aliphatic imines. But within these groups interesting differences also 

 assert themselves, which are solely due to the difference in the 

 position of the double bond. 



Whilst geranic acid is still a fairly active body, the dibasic acid 

 formed by oxidation of a methyl showed no action whatever even 

 when o,i g. were injected into a frog. 



Between a- and /?-cyclogeranic acids, important differences became 

 apparent, inasmuch as a-cyclogeranic acid acted like citral and geranic 

 acid, though more feebly, whilst /?-cyclogeranic acid was without any 

 action whatever 2 ), even in a quantity of 0,3 g. 



In what manner a difference in the position of the double bond 

 influenced the action was proved by R. Matzel 3 ), who examined at 

 my instigation the two isomeric terpineols. 

 CH CH^CH, 



M.p. 32 . >C< )CH- C<f 



HO / \ / \CH q 



CH 2 CH 2 3 



C H C H C H„ 



M.p. 35°. CH 3 .c/ \CH-C(0H)/ CH3 



CH CH 2 



The combination -products with glycuronic acid isolated from the 

 urine of the animals showed differences in the optical behaviour; the 

 melting points of the free acids also were different. 



The two terpineols can be converted by abstraction of water into 

 the terpene limonene; the same may also indirectly be converted over 



1 ) H. H il de brand t, Arch. f. exp. Pharmakol. 46 (1901). 



2 ) H. Hildebrandt, ibidem 46 (1901). 



3 ) Arch, internat. de Pharmacodyn. 14 (1906). Comp. Report October 1905, 88. 



