40 Anniversary Meeting. [Nov. 30, 



the fermentable liquid, prevented the entrance of the vibrios which 

 he had observed, and prevented the fermentation. It had been 

 reasonably suggested that fermentation or putrefaction might be a 

 purely chemical process produced by a quasi-chemical agent or 

 poison secreted by a living organism ; but Helmholtz's observation 

 disproved this supposition almost certainly, because any such chem- 

 ical substance in solution would pass by diffusion through the 

 bladder, and produce its effect without any direct action of the living- 

 creatures. Although Helmholtz himself was characteristically philo- 

 sophical and conscientious in not claiming, as absolutely proved, 

 what he had only rendered probable, it is certain that this early work 

 of his on putrefaction and fermentation constituted a very long step 

 towards the great generalisation of Pasteur, adverse to spontaneous 

 generation, and decisive in attributing to living creatures, born from 

 previous living creatures, not only fermentation and putrefaction, but 

 a vast array of the virulent diseases and blights, which had been most 

 destructive to men, and the lower animals and crops and fruits. Tt 

 is well that Helmholtz himself lived to see the great benefits con- 

 ferred on mankind by Pasteur's work ; and by the annulment of the 

 deadliness of compound fractures and the abolition of hospital 

 gangrene in virtue of Lister's antiseptic treatment ; and by the 

 sanitary defences against fevers and blights, realised by many other 

 distinguished men as practical applications of the science which his 

 own typhus fever of 1841 helped so much to create. 



Close after his work on this subject and on animal heat, followed 

 investigations on the velocity of transmission along the sensory 

 nerves of the disturbance to which sensation is due, the time which 

 the person perceiving the sensation takes to decide what to do in 

 consequence, and the velocity of transmission of his orders along the 

 motor nerves to the muscles which are to carry out his will. Results 

 of the highest scientific interest and of large practical importance 

 were given in two great papers published in 1850.* These were 

 followed a few years later by his " Tonempfindungen," a great 

 work, not merely confined to the perception of sound, but including 

 mathematical and experimental investigations on the inanimate 

 external influences concerned in sound, investigation of the anatom- 

 ical structure of the ear in virtue of which it perceives sound, and 

 applications to the philosophical foundation of the musical art. 

 which holds a unique position in the literature of philosophy, and is 

 certainly a splendid monument to the genius and indomitable working- 

 power of its author. Another great work of Helmholtz is his 

 " Physiologische Optik;" who shall say which of the two books is 

 the more important, the more interesting, or the more valuable? 

 Each of them has all these qualities to a wonderfully high degree. 

 * Helmholtz'a ' Wissenschaf tliche Abhandlungen,' p. 763861* 



