. A text-book of human physiology . 47 himself justified in concluding that animals have a peculiar kind of elec-tricity and that it is of very great importance in the functions of the animalbody; in fact, physiologists of that time thought their dream of a vital forcewas at last to be realized. It was reserved for the discriminating insight of Yolta to show that thesecontractions are conditioned upon the dissimilarity of the two ends of themetal touching the moist conductor, and upon the production thereby of agalvanic arc. Further investigation proved, however, that electrical differ-ences o
. A text-book of human physiology . 47 himself justified in concluding that animals have a peculiar kind of elec-tricity and that it is of very great importance in the functions of the animalbody; in fact, physiologists of that time thought their dream of a vital forcewas at last to be realized. It was reserved for the discriminating insight of Yolta to show that thesecontractions are conditioned upon the dissimilarity of the two ends of themetal touching the moist conductor, and upon the production thereby of agalvanic arc. Further investigation proved, however, that electrical differ-ences of potential do occur in the animal body. The events historically mostimportant from this point of view are: the discovery of the so-called frogcurrent—i. e., of a current running from the feet to the head of the frog(Xobili, 1827) ; the demonstration that the isolated muscle under definitecircumstances gives a regular current (Matteuci and Du Bois-Keymond,1840-1843); the discovery of the electrical variations in muscular activity. Fig. 29.—Schema representing the current of injury, or demarcation current, in a muscle, after Foster. (Matteuci and Du Bois-Reymond, 1842); and the discovery of the nervecurrent and its variations (Du Bois-Reymond. 1843). The object most used in these investigations is cross-striated muscle. Iftwo points of an exsected muscle be connected with a galvanometer an excur-sion of the needle nearly always occurs; between tlie two points of the musclethere is, therefore, a difference in tension. More detailed study has shown thatthese tension differences are perfectly regular, and in muscles with parallelfibers they have been found to take the following form (Du Bois-Reymond)(cf. the schema in Fig. 29). If a hmgitudinal surface and a transversely cutsurface of such a muscle be connected with a galvanometer, a current isobtained, which in the muscle is directed from the transverse to the longi-tudinal surface, and which reaches its greatest intensity (0.
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