166 ELECTRO-PHYSIOLOGY CHAP. 



muscular integument, about 1'3 mm. thick in the rabbit, which 

 extends from the hilum of the kidney to the bladder, along the 

 psoas muscle, with a surface of about 11 cm. The muscular 

 sheet, which lies between the adventitia and the mucous membrane, 

 consists of a thin, internal, longitudinal layer, and an external, and 

 much thicker, circular layer. Both are composed of smooth, non- 

 membranous, mononuclear fibre-cells, about 0'2 mm. long, in 

 which hardly any perceptible outline can be detected in the 

 physiologically fresh condition. The muscularis, therefore, gives 

 the impression, even under a high power, of an almost homogene- 

 ous, transparent mass. It is only in the moribund condition 

 that fine strife the optical expression of the cell-borders- 

 appear between the pale nuclei. Within the connective tissue 

 of the adventitia there is a ramification of nerves, consisting for 

 the most part of pale fibres (Engelmann's "Grundplexus"), in which 

 there is a remarkable and complete absence of nerve-cells. Engel- 

 mann states that the number of nerve-endings within the mus- 

 cularis is much less than that of the smooth muscle-cells. This 

 point, however, requires further investigation with the recently 

 discovered methods, which would very probably reveal a great 

 abundance of nerves. 



As a rule the ureter that has been cautiously exposed 

 exhibits spontaneous waves of contraction, spreading peristaltically 

 at intervals (mostly from 10 to 20 sees.) from the kidney to the 

 bladder. " If a definite point is taken anywhere along the 

 ureter, a weak, momentary dilatation may usually be seen 

 at the segment implicated just before its constriction, after 

 which it becomes thin, cylindrical, and much paler. At the 

 same time the ureter moves perceptibly downwards (towards 

 the bladder). The velocity with which the waves of contraction 

 spread is so low that it can easily be determined. This is 

 effected either by counting the beats of a metronome set at -^ 

 or ^ sec., during the time at which the wave of contraction is 

 transmitted from one point of the ureter to another (one being 

 determined close to the kidney, the other at a more distant spot, 

 by two operators), or they record with a Marey's tambour the con- 

 tractions of two points remote from one another upon the ureter. 

 With a vigorous rabbit, at sufficiently high temperature, the 

 velocity was 20 30 mm. per sec.; in the cat and rat it appeared 

 somewhat greater " (Engelmann). 



