January 2, 1903.] 



SCIENCE. 



15 



■wonder if any of you really doubt that 

 every notion in physics, definite or indefi- 

 nite, is associated with and derived from 

 a physical operation, and that absohitely 

 the only way to teach physics to young 

 men is to direct their attention to that 

 marvelous series of determining opera- 

 tions which bring to light those one-to-one- 

 correspondences which constitute the ab- 

 stract facts of physical science. If you 

 do, I am bound to say I do not think much 

 of your knowledge or teaching of physics. 

 I think that the sickliest notion of physics, 

 even if a student gets it, is that it is 'the 

 science of masses, molecules and the ether. ' 

 And I think that the healthiest notion, 

 even if a student does not wholly get it, is 

 that physics is the science of the ways of 

 taking hold of bodies and pushing them! 

 W. S. Franklin. 



INCOMPLETE OBSERVATIONS^ 

 In scientific literature many observations 

 are recorded which, from the experimental 

 proof ofl'ered, have been generally recog- 

 nized as true, but which may be classed as 

 incomplete, owing to the fact that the 

 methods of investigation employed de- 

 stroyed conditions that were later found 

 to exist, or that subsequent discoveries 

 modified the conclusions reached at the time 

 of the original investigation. 



As an illustration of this proposition the 

 theories of alcoholic fermentation may be 

 cited. The members of Section C will 

 readily recall the long and bitter contro- 

 versy which was waged between the two 

 great masters, Liebig and Pasteur, and 

 their respective adherents as to the true 

 cause of this phenomenon. 



It is interesting at this time, in the light 



• Address of the Chairman of Section C and 

 Vice-President of the American Association for 

 the Advancement of Science, read at the Washing- 

 ton meeting, December 29, 1902. 



of recent observations, to compare the two 

 opposing theories. 



According to Liebig alcoholic fermenta- 

 tion is caused by the decomposition of 

 complicated nitrogenous bodies designated 

 by him as putrescible material, and the 

 molecular disturbance thereby produced is 

 imparted to the fermenticible substance, 

 sugar, and breaks it up into simpler bodies, 

 alcohol and carbon dioxide. 



The vitalistic theory, revived by Pas- 

 teur and brought to general recognition by 

 his masterly and convincing experiments, 

 teaches that alcoholic fermentation takes 

 place only in the presence of a living micro- 

 organism known as the yeast plant, and 

 that the phenomenon of fermentation is 

 intimately connected with the life process 

 of this organism. The most convincing 

 proof in support of the vitalistic theory 

 was furnished by Pasteur in his methods 

 of preventing fermentation and allied 

 phenomena by simply heating perishable 

 bodies to a temperature high enough to 

 kill the living germs. In the case of 

 acetic acid fermentation he showed that a 

 temperature of 60° was sufficient to de- 

 stroy the vinegar plant. At this^ tempera- 

 ture, he argued, the nitrogenous bodies, 

 which Liebig claimed as the actual fer- 

 ments, would remain intact. In spite of 

 this, however, he showed that further fer- 

 mentation was completely arrested so long 

 as living germs were excluded. 



Although the work of Pasteur was of 

 the greatest importance to science and hu- 

 manity, and his experimental evidence for 

 the establishment of the vitalistic theory 

 of fermentation was of the highest order,.. 

 yet to the minds of many it was never en- 

 tirely clear that the rival theory was com- 

 pletely overthrown. For a long time, how- 

 ever, the vitalistic theory had clear sailing. 

 But the observations which led to its adop- 

 tion remained incomplete until a few years 



