As pointed out by Elliott1 more than twenty years ago, vesical innervation varies in different animals and, as shown by recent writers, the resultant stimuli passing up and down healthy nerves of the same species vary, to a certain extent, in the nerve paths followed to and from the bladder. Furthermore, the arrangement of the healthy vesical unstriped musculature varies when a series of empty, partly filled and filled cadaver bladders are compared. Therefore, the mass of conflicting experimental evidence that has accumulated with regard to the physiology of micturition is not to be wondered at. It is my purpose in this paper to present briefly some recent discoveries as to the physiology, and then to apply these facts in determining the pathology of bladder conditions by means of a new vesical pressure volume and time recording instrument. ANATOMIC MECHANISM OF MICTURITION The high lights of the more recent