M. Pasteur on Aspai-tic and Malic Acids. 277 



stances upon vvhich chemical influence is exerted; they are the 

 mechanical expression of their actual mode of existence, such as 

 it presents itself to our observation. But the vital organism 

 gives rise to a number of compounds, the parts of which chemi- 

 cally similar have an intimate, and, as it were, natural correlation 

 with each other, which is due to their physiological mode of ge- 

 neration. These substances are called organized. The chemical 

 corpuscles of which they are composed, being considered inde- 

 pendently of any relative coordination, are called organic bodies, 

 in allusion to their natural origin, without, however, attributing 

 to their simple elements any other properties than those which 

 they evince in the generality of combinations into which they 

 enter. Can it be that the deUcacy of the processes by which 

 these invisible corpuscles ai-e united, impresses upon them a 

 peculiar interior organization ? We are unable to answer this 

 question. Hitherto the rotatory power of molecules has only 

 been established in that class of substances elaborated by vital 

 organisms. 



Without being acquainted with the nature of the particular 

 forces which emanate from the separate corpuscles of which each 

 substance is composed, experience has proved that those which 

 chiefly determine chemical actions exercise influences, the inten- 

 sity of which decreases very rapidly when the distance is increased; 

 for all the different phseuomena of this kind take place within 

 distances which are to us entirely inappx-eciable. These phseno- 

 mena consist in the fact, that substances whose molecules mutu- 

 ally approach within these limits occasionally combine or sepa- 

 rate into coi-puscular systems difibring from those existing before. 

 These mechanical actions constitute what are called the chemical 

 combinations and decompositions. Probably only an imperfect 

 conception would be formed of these phsenomena, by comparing 

 them to the action of tw^o celestial nebulae which penetrated each 

 other. 



In spite of the excessive complication which this comparison 

 itself assigns to them, it is necessary, at least in imagination, to 

 distinguish two kinds of phajnomena in these reactions, diff"ering 

 from each other in the mechanical conditions of their fulfillment. 

 The former take place when the mutual distances of the corpus- 

 cles which react upon each other are so great in comparison to 

 their actual dimensions, that all the elements of the mass of each 

 coqjuscle of a similar nature exercise actions whose intensities 

 are virtually equal, whatever may be their relative situation in 

 its interior. The other phsenomena begin to take place when the 

 mutual distances of the corpuscles have become sufficiently small, 

 that the relative situations of the elements of their mass produce 

 .sensible inequalities in the absolute intensities of their individual 



