286 M. Pasteur on Aspartic and Malic Acids. 



acid derived from the fumarate possessed, like tbe natural acid, 

 a rotatory power, in which case it would be the fii-st instance of 

 an active body which could be derived from an inactive body ; 

 or the artificial aspartic acid would be inactive, and in that case, 

 in spite of the identity of its chemical composition, it would be 

 molecularly different from the natural acid. The latter conjec- 

 ture was found to correspond with the fact. M. Pasteur esta- 

 blished its coiTectness directly upon the small quantity of the 

 artificial acid which M. Dessaignes was so obliging as to provide 

 him with, after he had informed him of the unexpected interest 

 which was attached to it. He also recognised in several of the 

 small crystals a difference of form from that of the natural acid. 

 The agreement of these two characters established the distinct 

 nature of the new product; and the ingenious chemist who 

 obtained this body doubled his right to the gratitude of science 

 by evincing such generosity as to communicate it, that it might 

 be investigated from a point of view apart from his especial 

 studies. But these first observations only contributed to point 

 out a fertile subject of investigation to any one who should follow 

 it up in all its details with patient industry. M. Pasteur has de- 

 voted a whole year to effecting this object, and the results which 

 he has obtained are collected in the memoir which he has just 

 submitted to the public. We cannot do more than give a brief 

 summary of it. 



He siibmitted the two aspartic acids, the active and the in- 

 active, to all the trials, both physical and chemical, by which the 

 identity or difference of their molecular constitution could mani- 

 fest itself. They were first examined in their uncombined state : 

 he determined comparatively their elementary composition, their 

 respective crystalline forms, their density and solubility in the 

 same solvents. He then combined them with bases, and deter- 

 mined the composition of their respective salts, which he found 

 constantly identical in pairs, with the peculiarities of difference 

 of form, which he carefully estimated. He finally traced them 

 through their chemical derivatives ; and by subjecting them to 

 parallel modifications of treatment, he obtained from them two 

 malic acids, the one possessing and the other destitute of rota- 

 toiy power, like the bodies from which they were produced. He 

 then submitted these two products to the same series of tests 

 which he had applied to their generators, that is to say, he de- 

 termined in a parallel manner their crystallographic, physical, 

 and chemical characters, as well in combination as in a free state. 

 It is in this manner that the unexpected problem which was 

 presented to him has been studied in all its branches, all the 

 particulars which it was capable of affording, and by all the pro- 

 cesses of observation and experiment which could be applied to it. 



