ii CHANGE OF FORM IN MUSCLE DURING ACTIVITY 167 



With artificial (mechanical) stimulation the contraction is 

 transmitted from both sides of the point excited, while in regard 

 to velocity no perceptible difference between the peristaltic 

 and anti-peristaltic waves can be determined. It is, however, 

 remarkable that the contraction only appears with direct excita- 

 tion of the muscularis. "Neither by pressure of the mucous 

 membrane, or adventitia with the nerve -plexus, nor of the 

 greater nerve-trunks at the hilus and bladder, can a contraction 

 be discharged anywhere in the ureter. Local excitation always 

 produces localised contraction, spreading slowly on both sides. If 

 the ureter is divided, crushed, or tied at any point of its length, a 

 contraction will occur above or below the spot after every excita- 

 tion, and is transmitted 011 both sides of the excited part, but 

 never passes beyond the dead point. Since even short excised 

 strips of the ureter react peristaltically when excited, we cannot 

 assume, in view of the structure, that ganglion-cells are respon- 

 sible for the appearance of the peristalsis ; the ureter rather 

 reacts to mechanical excitation in every case " as though it were 

 a single, gigantic, hollow muscle-fibre." We have already seen what 

 an extraordinary influence temperature has upon excitability and 

 conductivity in the ureter, as well as the extraordinary vitality of 

 muscles that are deprived of normal nutrition. Each wave of 

 contraction produces a temporary depression of excitability and 

 conductivity in the sheet of muscle, from which it only recovers 

 during the subsequent diastole and interval (just as in the striated 

 muscle-nets of insect intestine). Every diminution of conduct- 

 ivity expresses itself by the gradual disappearance of the wave 

 of contraction, which, whether spontaneous, or artificially excited, 

 becomes weaker in proportion with the length of its course, and 

 finally dies out even in immediate proximity to the point of 

 excitation. Finally, instead of the advancing wave, there is left 

 only a protracted contraction in the part immediately adjacent to 

 the point of excitation the analogue of the idio-muscular con- 

 traction in striated muscles. The rapidity with which movement 

 is transmitted varies with the conductivity, as is clearly and 

 easily shown by cooling and warming. Since every wave of 

 contraction affects the time-relations of the succeeding wave, it is 

 a matter of course that if the spontaneous contractions succeed 

 one another at irregular periods, those which are preceded by a 

 short pause are transmitted more slowly than those which follow 



