268 HERMANN VON HELMHOLTZ 



In his experiments on the transmission of excitations in 

 nerve, Helmholtz had remarked (as already noted by others) 

 that electrical induction shocks had little effect upon the 

 deeper-lying nerves of the human body, while it is an easy 

 matter to produce contractions, even in the deeper nerves, by 

 the constant currents of a battery of ten to twenty platinum- 

 zinc cells. In a lecture given to the Nat. Hist. Med. Ver. at 

 Heidelberg on February 12, 1869, 'On the Physiological 

 Action of Brief Electrical Shocks within Extended Conductors,' 

 he described the experiments made to establish these facts 

 on the thigh of the frog, which proves the accuracy of his 

 observations. But the explanation of these phenomena, which 

 he referred back to the investigation of the distribution of 

 electrical discharges in extended conductors, involved a certain 

 knowledge of the oscillation-frequency of the currents in an 

 induction coil, whose terminals are connected with the coatings 

 of a Leyden jar. In another lecture delivered on April 30, 1869, 

 to the same Society, ' On Electrical Oscillations/ Helmholtz 

 presented the results of his experiments in this direction, in 

 which a frog's nerve was used as current-indicator and reagent 

 for the detection of the electrical movements, and in which the 

 electrical oscillations took place between the coatings of 

 a Leyden jar, in a complete and uninterrupted circuit which 

 had no spark gap. It was then found that in using a Grove's 

 cell for the primary current, the total duration of the perceptible 

 electrical oscillations in a coil joined up with a Leyden jar 

 was about -fa of a second. The determination of the oscillation- 

 frequency is required to make it possible to set up exact 

 experiments in proof of the above facts. 



Helmholtz gave an address at the Opening of the Natural 

 Science Congress at Innsbruck in September, 1869 (which he 

 attended with his wife), entitled ' The Aim and Progress of the 

 Natural Sciences.' It was designed to give an account of 

 ' the progress of natural science as a whole, the aims for which 

 it strove, and the magnitude of the steps by which it advanced 

 towards its goal '. 



Amid the wide circle of his undertakings we find a solitary 

 note on Hay-fever, taken from a letter addressed to Binz, and 

 published in 1869, in Virchow's Archiv f. path. Anatomic. In 

 an attack of hay-fever (from which Helmholtz was a chronic 



