Grundstzliche Eigenschaften der mechanischen Ttigkeit der Dnndarmlngsmuskulatur

Small strips of the longitudinal muscle (10–1 mm) of the rabbit's intestine showed regular, rhythmic phasic contractions in Tyrode solution for a long time. Single rectangular pulses with duration of 5 msec were applied to these strips with the following results: 1. A weak stimulus caused extracontraction, the height and latency of which did not change with increasing stimulus, when the stimuli were applied at the same moment of the phasic contraction. The extracontraction of the longitudinal muscle strip, therefore, obeys the all-or-none-law. 2. The latency of the extracontraction and the strength of the threshold stimulus which caused the extracontraction, varied with the change of the moment of stimulation during the phasic contraction. The recovery curve showed the variations of both these values. 3. The absolute and relative refractory period of the phasic contraction were measured. The former period at the beginning of the contraction lasted 0.1 or 0.2 sec and was followed by the latter. 4. A strong stimulus provoked a tonic contraction, the height of which was increased with increasing stimulus. Thus the tonic contraction of the longitudinal muscle strip did not obey the all-or-none law. The threshold stimulus provoking the tonic contraction did not change according to the moment of stimulation at the phasic contraction and remained constant with the specimen. 5. Both threshold values varied with the section of the small intestine from which the muscle strips were taken. The threshold stimulus causing the extracontraction was lower in the oral than in the anal part. Reversely the threshold stimulus provoking the tonic contraction was lower in the anal than in the oral part.