238 PHYSIOLOGY CHAP. 



frequent rhythm (14-22 per minute), the latter a. slower rhythm 

 (12-18 per minute). 



In dogs with intestinal fistulae near the valve of Bauhin, 

 Radziejeswski observed that the flow of the intestinal contents 

 through the fistula commenced 1 |-2| hours after a meal : that the 

 first expulsory movements occurred at intervals of 5-30 minutes ; 

 the later ones at greater intervals : and that some 6 hours after 

 the meal pauses or rests of many hours could be seen. There are 

 accordingly periods of activity and of repose, although it is not 

 possible to establish fixed data in regard to duration and rhythm 

 of the peristaltic motions. The results -of Braun and Lossnitzen 

 differed little. 



The movements of the gut can be provoked or modified 

 artificially by mechanical, thermal, electrical, and chemical 

 stimuli ; as well as by the effects of hyperaemia and of 

 anaemia ; or by chemical agents introduced into the intestine. 

 The most important fact established by direct mechanical or 

 electrical stimulation of the intestine is that the contraction 

 excited at the point of stimulation spreads in both directions along 

 the bowel; in some species of animals, indeed, the curious fact 

 appears that the movement is propagated more extensively up- 

 wards than downwards, i.e. more in the antiperistaltic than in the 

 peristaltic direction (Engelmann). Nothnagel's experiments, how- 

 ever, show that the effect of excitation varies with the nature of 

 the stimulus. If a crystal of sodium chloride be applied to the 

 outer surface of the intestine, a contraction is produced which is 

 propagated upwards for some centimetres in the direction of the 

 pylorus ; a crystal of potassium chloride, on the contrary, produces 

 only a local spasm. 



The dissimilar reaction of the longitudinal and the circular 

 muscle fibres to stimulation with the constant current is interest- 

 ing. Schillbach (1887) first noted that on bringing the kathode 

 into contact with the external surface of a loop of intestine a 

 localised contraction results, while on placing the anode in contact 

 the local contraction is transformed after a few seconds into 

 a peristaltic wave of contraction, which moves from the point 

 stimulated along the loop in both directions. Hillel Jafe* (1889) 

 confirmed this observation, and interpreted the primary effect of 

 the anodic closing stimulus as an effect of contraction of the 

 circular muscles of the muscular coat. Biedermann and Sinchovitz 

 (1889) extended these observations, and gave a better explanation 

 of their significance. According to these authors the effect of the 

 unipolar anodic closing stimulus is to produce a ring of constriction' 

 by the local contraction of the circular muscles. The effect of the 

 unipolar kathodic closing stimulus, on the contrary, is a slight 

 local contraction of the longitudinal muscles. Luderitz (1891) 

 also confirmed these data and their interpretation. 



