772 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1913. 



If this seems exaggerated oue should read the writings of u Mr. vau't 

 Hoff. full of bad tricks of the imagination, which I should prefer to ignore 

 if a distinguished chemist hud not given him his patronage. This Dr. van't 

 Hoff. employed in a veterinarj' school at Utrecht, takes no pleasure, it appears, 

 in exact chemical research. He has found it more comfortable to mount a 

 veterinary Pegasus and to announce how, in his mad flight through a chemical 

 Parnassus, the atoms have appeared' to him to be scattered in space. 



Such a method of treating scientific questions which is not too far removed 

 from a belief in sorcery and spirits is considered legitimate by a chemist like 

 Wislicenus, whom we have always known as a serious scientist. By this act 

 he excludes himself from the ranks of exact scientists and enters the category 

 of those natural philosophers of evil fame whom only a subtle medium sep- 

 arates henceforth from the spiritists. 



To this phillipic our scientist made a most sober and serious re- 

 sponse. He prefaced to an article published in 1877 a few dignified 

 but not unforceful words, and in October, 1878, as professor at Am.s- 

 terdam, he opened his course by reading from the text, Kolbe's at- 

 tack, taking occasion not to open a direct dispute but to defend se- 

 renely the importance and legitimacy of the intervention of creative 

 imagination in the exact sciences. 



But the address of Kolbe was no more efficacious than the objec- 

 tions of Berthelot in barring the way of stereochemistry in its march 

 toward success. Hans Landolt, the best authority in the domain of 

 chemical optics and polarimetry, realized that the new views were in 

 accord with the facts of experience; and Piutti was one of the first, 

 with his researches into the stereo-isomeric asparagines, to bring new 

 facts to the aid of the .new theory. More important still were in- 

 vestigations carried on in Germany after 1885. Besides those of 

 Wislicenus on the stereo-isomerism of unsaturated compounds, we 

 must remember those of A. von Baeyer on the stereo-isomerism of the 

 hydroaromatic compounds and on the stereochemistry of cyclic com- 

 pounds in general. 



But the new doctrine obtained its greatest triumph when Emil 

 Fischer, using it as a foundation, was able to solve for the first time 

 the great problem of the composition of sugars. This impenetrable 

 forest, which had defied until then the efforts of chemists, became 

 suddenly light when an experimenter of such exceptional value held 

 in his hand the thread of Ariadne, which alone could guide him to- 

 ward the goal. 



The succeeding history is only a succession of new conquests. V. 

 Meyer and Hantzsch and "Werner have shown that in the unsaturated 

 nitrogen compounds like oximes, there could occur isomers of the cis 

 and trans types; it is thus that the stereochemistry'- of nitrogen came 

 into existence. Still more recent researches, among which we must 

 mention first those of Pope, have demonstrated that when an atom 

 of any tetravalent element whatever becomes asymmetric, this causes 

 the appearance of optical activity and the existence of two stereo- 



