1894.] President's Address. 39 



student-philosophers, and must soon have convinced the elder men 

 that, whatever may be the real efficiency of vitality, vast and wonder- 

 ful as it is, it does not include the performance of work without 

 drawing upon a source of energy. This conclusion had been virtually 

 foreseen before the end of last century by Rumford and Davy, and 

 had been clearly stated and powerfully supported by Joule and 

 Mayer a few years before Helmholtz found it for himself and success- 

 fully persuaded others of its truth. 



It is interesting for us now to know that, while thus contributing 

 so effectively to the abandonment of the old doctrine that vital 

 " force " can work without drawing on an external source of energy, 

 Helmholtz was even more effectively concerned in the establishment of 

 a new doctrine which has given a vast extension to the province of life, 

 previously perhaps undreamt of, but now universally recognised as 

 thoroughly well established, and supremely important in modern 

 physiology and medicine. On recovering from a typhus fever in the 

 autumn of 1841, at the age of 20, the last year of his undergraduate 

 course in the Army Medical School of the Friedrich Wilhelm's 

 Institute, he spent the accumulations of his income, which free treat- 

 ment at the hospital during his illness had left him, in the purchase 

 of a microscope, an instrument then but little used in medical educa- 

 tion. He began immediately to use it, and made some important 

 observations on the ganglion cells of invertebrates, which, at the 

 suggestion of his master, Johannes Miiller, he took as the subject of 

 his inaugural thesis for the doctor's degree, in November, 1842, and 

 which was his first published work.* With the same microscope, he 

 observed vibrios in putrefying liquids, which he described in his 

 second published paper (1843), " On the Nature of Putrefaction and 

 Fermentation." His distinguished comrade, Schwann, in the labora- 

 tory of Johannes Miiller, had already shown that vegetable cells are 

 present in fermenting solutions of sugar, and that air, which had 

 been highly heated, was incapable of exciting the fermentation which 

 the access of ordinary atmospheric air was known to produce. 

 Helmholtz found that oxygen, yielded by the decomposition of water 

 in flasks containing small pieces of boiled meat, did not produce 

 putrefaction. Thus the doctrine, held perhaps by all before them, 

 and certainly supported by the great Liebig, that putrefaction and 

 fermentation are purely chemical processes of eremacausis (or slow 

 combustion), produced by oxygen, was thoroughly disproved by the 

 two young investigators. But Helmholtz went farther, and showed 

 almost certainly that the actual presence of a living creature, vibrio, 

 as he called it, bacterium, as we more commonly call it now, is 

 necessary for either fermentation or putrefaction. He proved by 

 experiment that a partition of moist bladder, between the yeast and 

 * Helmholtz's ' Wissenschaftliche Abhandlungen,' vol. 2, p. 663. 



