[85] _Piper_: “Ueber die Leitungsgeschwindigkeit in dem markhaltigen menschlichen Nerven.” The same: “Weitere Mitteilungen über die Geschwindigkeit der Erregungsleitung im markhaltigen menschlichen Nerven.” Pflügers Arch. Bd. 127, 1909. These differences may be explained in a _large_ measure by the variety of the methods used, in part also by the difference in the structures. The methods employed for the study of the velocity have also been used to solve the question, whether the velocity of the excitation wave in its course over the nerve meets with a decrement as it moves further and further away from the point of stimulation. Here the endeavor was made to study the difference in time of the latent period, which is observed by the indicator, when the nerve is stimulated at two points at different distances from the muscle, used as an indicator, or from the wires leading the current to the indicator. The more recent investigators, as _René Du Bois-Reymond_,[86] _Engelmann_,[87] _G. Weiss_,[88] have arrived at the same conclusion, that the rate of conductivity in the medullated nerve under normal conditions is the same at all distances from the point of stimulation. (Figure 20.) [86] _R. Du Bois-Reymond_: “Ueber die Geschwindigkeit des Nervenprincips.” Arch. f. Anat. u. Physiol. physiol. Abt. Suppl. 1900. [87] _Engelmann_: “Graphische Untersuchungen über die Fortpflanzungsgeschwindigkeit der Nervenerregung.” Arch. f. Anat. u. Physiol. physiol. Abt. 1901. [88] _G. Weiss_: “La conductibilité et l’excitabilité des nerfs.” In Journ. de Physiol. et de Pathol. générale 1903. The medullated nerve shows, therefore, under normal conditions neither a decrement of its conductivity, nor of its _irritability_, as the distance of the wave of excitation increases from that of the position of stimulation; this means, in other words, that excitation is conducted with the same intensity with which it is started, and with a constant rate throughout the entire course of the nerve. [Illustration: Fig. 20. Curves of muscle contraction obtained by stimulation of 3 and 4 points situated at equal distances from each other on the sciatic nerve of the frog. The increase of length of the nerve stretch corresponds with an equal increase of the latent period of contraction. From this follows, that the rapidity of the wave of excitation is the same at all points of the entire length of the nerve. (After _Engelmann_.) ]