COMBINATIONS BETWEEN ACTIVE MOLECULES 41 



right- and left-handed tartrates in combination even with 

 the same organic alkali. In short, we observe some 

 differences which can be attributed legitimately only to 

 the reciprocal influences of the acid and the base in 

 combination. 



And, thenceforth, we are authorized to philosophize 

 with Pasteur. It is very probable that all natural, 

 active bodies present, like tartaric acid, at least three 

 forms, the right, the left, and the para. Then when we 

 combine two substances each of which has its right, left 

 and inactive form, it is possible to obtain nine different 

 combinations, identical as far as the number and nature 

 of the atoms is concerned, but different in their arrange- 

 ments. This difference of arrangement will admit 

 of the addition of an unequal number of molecules 

 of water of crystallization which will be more or less 

 difficult to drive away with heat. It will involve, 

 furthermore, differences in crystalline form, in solu- 

 bility, and in chemical stability. On the whole, it is 

 sufficient to constitute nine different substances, which 

 number could be increased to sixteen if we take into 

 consideration, in addition to the three forms pointed 

 out above, the form by nature inactive, which Pasteur 

 had not yet discovered in the tartaric acid. 



Of a complete series there was no example at the time 

 when Pasteur worked, and I do not know whether there 

 is one to-day. Then, there were only some scattered 

 terms but these permitted the beginning of proof. 

 Precisely the combination of the right-handed tartaric 

 acid with the left appears in the forecasts 'above made, 

 and it is remarkable that one finds between the tartrates 

 and paratartrates differences of the same order as those 

 which we have just pointed out. The chemical com- 

 position is ordinarily not the same, the crystalline forms 

 are incompatible, the solubilities are different, etc. 



