Several recent studies on the urinary bladder indicate that the detrusor smooth muscle and vesical wall possess independently functions once considered to require neural regulation. Nesbit et al.1,2demonstrated that the intravesical pressure-volume curve in both' man and dog remained unchanged after spinal anesthesia and spinal shock, and Tang and Ruch3confirmed the opinion that bladder "tonus" is non-neurogenic, in contrast with micturition contractions, which depend upon spinal-reflex integrity. The present study emphasizes further the autonomous contribution of the detrusor muscle to bladder function. When fluid fills the normal mammalian urinary bladder, two types of contractile responses may ensue: low-grade, relatively brief, rhythmically recurring contractions, and high-intensity, sustained micturition reflexes. The relationship between these reactions has not been explored extensively, and many bladder function studies either fail to mention rhythmic contractions or dismiss them as abortive micturition reflexes. This omission decreases understanding, since the presently reported material