348 EBEN J. CAREY 



experiment May 21st, after the dog had had a night's rest. A 

 constant volume and pressure were maintained throughout the 

 observation. The varying irritabihty and response of the bladder 

 during this observation are clearly shown. At the beginning, 

 line 1, the bladder is not so irritable as subsequently, lines 2 to 5. 

 At first the contractions are few in number, but as the bladder 

 becomes more irritable to the constant hydrodynamic tensile 

 stimulus it responds with more celerity. 



By reducing the pressure the vesicular contractions are retarded 

 (figs. 15 and 16, line 1), and by complete inhibition of the circula- 

 tion, no contractions are elicited (fig. 16, lines 1, 2, 3, 4, 5, 6 and 7). 

 The stimulus that causes the rhythmic beat of the bladder is 

 hydrogenic in nature. The rhythmic beat is dependent also on 

 the irritability of the responding mechanism. This fact is 

 immediately evident by inspecting (fig. 14, lines 1, 2, 3, 4, and 5). 



Acceleration of the vesicular beats may be induced by increasing 

 the volume and pressure of the fluid flowing into the bladder. 

 This is clearly shown in (fig. 20). By regulating the fluid pres- 

 sure, a condition may be induced whereby the bladder responds 

 vigorously and regularly. When the stimulus was so regulated 

 that sixty-five to seventy-five beats per minute were established, 

 the bladder reacted with regularity and absolutely no distress 

 was experienced by the puppy. The dog could be maintained in 

 a recumbent position for hours and would breathe regularly even 

 sleep for half an hour or so while the bladder was pumping at the 

 rate of seventy-five times per minutes. There were no conscious 

 efforts on the part of the dog with these rhythmic contractions of 

 the bladder once the experiment was under way and the vesicular 

 irritability had been reestablished after the dog had had a night's 

 rest. Figure 14 shows the bladder beating at the rate of about fifty 

 per minute during one hour and fifteen minutes of observation; 

 this record was made with a slow drum. The puppy slept practi- 

 cally throughout the time that the manometric curves were being 

 recorded. 



The structure of these pressure curves is definitely shown by 

 figures 17 and 18 made on a fast drum. The up-stroke represents 

 bladder distention with the concomitant increased back pressure 



