Hermann von Helmholtz

Bayliss says Helmholtz (1850) first definitely showed that an impulse takes time to cross a nerve. He adds that this affected views of mental phenomena, because a nervous process could now be expressed as a number¹. The frog value was 29 metres per second. Bayliss sets it beside Piper's 1912 figure of 123 metres per second in man, taken with the string galvanometer². Bose cites Helmholtz's human value of about thirty-three metres per second. He notes that later determinations gave twice as much, and that the record is hard to read exactly³.

Verworn reports that Helmholtz discovered a change in the muscle curve with fatigue. The curve falls in height and grows longer, mainly because the descending limb lengthens⁴. In psychology, James treats Helmholtz as holding that colour perception, like space perception, is intellectual. Simultaneous colour contrast is explained as an unconscious inference. James accepts the weight of this authority but disputes it, and he follows Hering's view of contrast⁵. Rádl says physiologists such as Helmholtz tried to fit their views to the doctrine of specialised nerve cells⁷.

Verworn records that Helmholtz and Sir William Thomson, some years after Richter, discussed whether life might have reached the earth from other heavenly bodies. Both called the idea not unscientific⁶. D'Arcy Thompson cites Helmholtz's 1873 paper on geometrically similar motions of fluid bodies and its application to steering balloons. He notes that Müllenhof criticised the result in the 1880s, which Thompson calls somewhat rash⁸.