26 HERMANN VON HELMHOLTZ 



of Euler, Daniel Bernoulli!, d'Alembert, and Lagrange, mathe- 

 maticians of the previous century, and arming himself with 

 a small textbook of higher analysis he had plunged even as a 

 student, during the time of his assistant-librarianship at the 

 Institute, into the fundamental investigations of these great 

 mathematicians penetrating into the significance of the prin- 

 ciples of mechanics, as laid down by these immortal thinkers, 

 with which such metaphysical views were incompatible. 



The time was not yet ripe for bringing forward these 



universal and comprehensive ideas ; Helmholtz had learned 



from the stern methods of Johannes Muller that only definite 



and methodical experiment could make the general principles 



of science intelligible, and set them on a sure foundation. As 



soon as his doctor's examination was over, he applied himself 



in M tiller's laboratory to a problem which, on account of 



Liebig's work, was then in the forefront of interest. Helmholtz 



attacked it on far wider grounds, with the intention of bringing 



* the so-called ' vital forces ' within the scope of scientific study. 



I Liebig was engaged in a fierce campaign against the organ- 



/ ized nature of yeast, as discovered by Schwann and Cagniard- 



/ Latour, and its role in alcoholic fermentation, and upheld the 



I essentially chemical theory of fermentation and putrefaction, 



based on Gay-Lussac's experiments. Helmholtz immediately 



recognized the crucial importance of this question, and its 



close connexion with the possibility of perpetual motion, and 



set himself to decide the point. The economies of his winter's 



illness had provided him not only with a microscope for the 



morphological investigations described in his thesis, but also 



with the recently published Organic Chemistry of Mitscher- 



lich ; and in the early months of the year 1843, when he was 



not much hampered by his duties in the children's ward, he 



plunged into extended physico-chemical investigations which 



henceforward absorbed him. 



In this arduous and exhausting work he had to trust entirely 

 to himself, as he knew little of even the most important 

 publications on the subject. On July 25 he applies to his 

 father to procure him the necessary literature : ' Could you 

 be so good as to borrow of Professor Meyer, or through his 

 intermediation, by next Sunday afternoon, that treatise of 

 Mitscherlich on Fermentation which you mentioned the other 



