PHYSIOLOGICAL PSYCHOLOGY 79 



and power were joined to scientific competence. I, therefore, leave 

 them for a moment to take a glimpse — it can be no more — at the 

 strictly scientific interest as we see it illustrated in Johannes Miiller's 

 greatest pupil, Helmholtz (1821-1894). 



Helmholtz ranks not simply with the foremost scientific intellects 

 of the nineteenth century but with the master minds of all time. His 

 range, grasp and insight combined to render him monumental. A 

 contributor to at least eight sciences — physics, physiology, mathemat- 

 ical physics, meteorology, medicine, chemistry, anatomy and esthetics, 

 in three of them he stands high among the foremost. More than this, 

 as Volkmann has recalled, " one of his chief merits was to establish a 

 harmony between the vast accumulation of facts that characterized the 

 period comprehending the middle of this century and the more theo- 

 retical studies." 12 Besides, he possessed unusual manipulative skill, 

 his inventions of the ophthalmoscope and ophthalmometer alone would 

 have assured any ordinary reputation. Above all, he was a humanist, 

 being an accomplished musician, an art critic, and acquainted with the 

 trend of philosophical thought. His discoveries of classical grade 

 amaze one by their thoroughness and versatility. The conservation of 

 energy; the mechanism of the lens of the eye in relation to accom- 

 modation; the movements of the eyeballs with the attendant problems 

 of binocular and stereoscopic vision; the profoundest questions of 

 hydrodynamics, thermodynamics and electrodynamics, the last cul- 

 minating in the revelations of his favorite pupil, Heinrich Hertz; the 

 axioms of geometry; the dark places of meteorology; the deeps of 

 physiological optics and of mathematical physics, all bear witness to 

 his profound, masculine and subtle intellect. But, for our present 

 study, the palm must go to his long struggle with the difficulties of 

 sensation and perception. These absorbed his principal attention from 

 1852 till 1867 and, in a lesser degree, till his death. He laid the 

 foundation characteristically by his inquiries into the rate of nervous 

 impulse in the motor and sensory nerves, about 1850, and his first 

 paper, on sensation proper, followed in 1852. These labors were 

 crowned magnificently by the publication, in 1863, of his " Sensations 

 of Tone," and, in 1867, of his " Physiological Optics " — masterpieces 

 both. The former, which involved the most complicated research, has 

 earned the title, " the Principia of acoustics," and must be studied 

 long to be appreciated. For, it not only ranged over the entire subject 

 but, incidentally, raised important problems that belong elsewhere, 

 especially to the domains of phonology and esthetics. Questions about 

 the quality of the human voice and the absolute pitch of vowel sounds 

 lead us away from the physical and the physiological laboratory to a very 

 different environment. Similarly, the " Physiological Optics," with 

 12 " Hermann v. Helmholtz," J. G. McKendrick, p. 284. 



