HISTORICAL SECTION 
The occurrence and distribution of differences of potential between points upon 
the surface of excised nerve, was discovered in 1842 by Du Bois Reymond, published 
in 1 843, 1 and described in an exhaustive manner in his first collection of researches 2 in 
1 849. The general account given by him of this phenomenon provides one with an 
example of the possible truth and completeness of experimental observation. Rapidly 
as the research must have been carried through, for it forms only an incident in a 
larger theme, the statement is a perfect one, and an intimate acquaintance with the 
phenomenon reveals the amount of observation concealed behind each one of its care- 
fully considered sentences. The salient points were gathered into three generaliza- 
tions, the well-known laws of the nerve current. They define the spatial distribution 
of points upon the surface of the nerve, between which the differences of potential 
were (1) large, (2) small, (3) non-existent. 
These laws describe the ideal case, which it is carefully noted was rarely, if ever, 
obtained, and in their application to the facts of any single experiment are stated 
generally to require modification. The most important modifications being due to the 
occurrence of a potential difference between the two cross sections and to the disloca- 
tion of the equatorial point from the mid point of the nerve. 
Morgan, in 1863,' pursued the investigation one step further, and demonstrated 
the existence of a nerve current in minutely thin longitudinal fragments of nerve trunk, 
obtained for the experiment in a manner described by Harless 4 . He also noted the 
presence of 'weak longitudinal currents' in these fragments, and ascertained the 
symmetrical arrangement of potential distribution round an equatorial point. 
The remaining work which has been undertaken in this subject has, to a large 
extent, only been concerned with the comparison of results obtained from various 
nervous tissues, and with modifications devised to test theories of its mode of origin, 
or with results obtained in abnormal or pathological conditions of the nerve. 
The relation between the conditions thus found upon the surface of the nerve 
trunk, and its microscopical fragments, and the conditions of greater interest and 
importance legitimately inferred from a consideration of these to exist in the more- 
I. Du Bois Reymond, Poggendorf Annul. B(i. LXVIII. January, 1843. 2. Untersuchungen. II (1), p. 262. 
3. Charles E. Morgan, Reicherts Archi-u., 1863, p. 340 ; also Electrophysiolagy and Therapeutics, New York, 1868, p. 465 
4. E. Harless, Abhandl Konigl Bayeruch Akad. d. Wm. 2nd Class, Bd. VIII. Abth. II, p. $39. 
