26 LOUIS PASTEUK. 



occasion new facets were thus produced, and these 

 new facets showed the kind of dissymmetry which the 

 optical character demanded. Although he had to 

 limit his researches to those substances which, by 

 their ready crystallisation and the beauty of their 

 forms, lent themselves best to this class of proofs, the 

 results were so far in accord with the previsions of 

 theory, that no reasonable doubt could exist as to the 

 necessary correlation between dissymmetry and the 

 power to deviate polarised light. 



By these researches Pasteur was led to a conclu- 

 sion, which is worthy of the most serious considera- 

 tion, regarding the difference which exists between 

 mineral species and artificial products on the one 

 side, and the organic products which can be ex- 

 tracted from vegetables or animals on the other. All 

 mineral or artificial products for brevity let us say 

 all the products of inorganic nature have a super- 

 posable image, and are therefore not dissymmetrical, 

 while vegetable and animal products in other words, 

 products formed under the influence of life have an 

 image not superposable ; that is to say, they are 

 atomically dissymmetrical, this dissymmetry express- 

 ing itself externally in the power of turning the 

 plane of polarisation. If any exceptions exist they 

 are more apparent than real. Pasteur himself pointed 

 out some of them, while demonstrating at the same 



