178 IRRITABILITY 



succeeding one. With the isolated apex preparation of the 

 frog's heart an effect is produced which Bowditch 1 has termed 

 the "Treppe" and Tiegel, 2 Minot 3 and others have obtained the 

 same result for the skeletal muscle. The Treppe has been often 

 regarded as an expression of increasing of capability of the 

 muscle following each succeeding stimulus in spite of the fact 

 that it is physiologically incomprehensible that an isolated muscle 

 can become more capable by increased demands. Frohlich* first 

 threw light on this seeming contradiction by showing that the 

 increase in height of the muscle contraction in the Treppe is 

 in reality the first indication of the beginning of fatigue, and 

 Fr. Lee* arrived at the same result. The increase in height of the 

 contraction curve depends upon the retardation of the course of 

 contraction. As the contraction extends over the muscle sub- 

 stance in the form of a wave, a longer stretch of the muscle will 

 be in a state of contraction when the wave is more extended than 

 when it is shorter, that is, the shortening of the muscle will be 

 greater, the contraction curve higher, when the wave is more 

 extended. With increasing fatigue the retardation in the course 

 of contraction, as Rollet Q already has shown, becomes continu- 

 ously greater. (Figure 34.) The consequence of this retardation 

 in the course of contraction is, therefore, perceptible in the 

 rhythmically activated muscle in the form of contracture. As 

 fatigue increases, the muscle requires an increasing length of time 

 to relax to its full extent and in consequence the period between 

 the two stimuli is very soon insufficient for this to occur. There 



1 Bowditch : "Ueber die Eigenthiimlichkeiten der Reizbarkeit, welche die Muskel- 

 fasern des Herzens zeigen." Arbeiten aus der physiologischen Anstalt zu Leipzig VI 

 Jahrgang 1871, Leipzig 1872. 



2 Tiegel: "Ueber den Einfluss einiger willkiirlichen Veranderungen auf die 

 Zuckungshohe des untermaximal gereizten Muskels." Arbeiten aus der physiol. 

 Anst. zu Leipzig X Jahrgang 1875, Leipzig 1876. 



3 Minot : "Experiments on tetanus." Journ. of Anat. and Physiol. Vol. XII. 



4 Fr. IV. Frohlich: "Ueber die scheinbare Steigerung der Leistungsfahigkeit des 

 quergestreiften Muskels im Beginn der Ermudung. (Muskel Treppe), der Kohlen- 

 saurewirkung und der Wirkung anderer Narcotica (Aether, Alkohol)." Zeitschr. f. 

 allgem. Physiologic Bd. V, 1905. 



5 Frederic S. Lee: "The cause of the Treppe." Americ. Journ. of Physiol. Vol. 

 XVIII. 1907. 



6 Alexander Rollet: "Ueber die Veranderlichkeit des Zuckungsverlaufs quer- 

 gestreifter Muskeln bei fortgesetzter periodischer Erregung und bei der Erholung 

 nach derselben." Pflugers Arch. Bd. 64, 1896. 



