Excerpt from Archives of Surgery, 1921, Vol. 3The trigonal muscle is Of particular interest in a study of the mech anism of micturition, because Of its peculiar anatomy and close relation ship with the so-called vesical sphincters. The opening of the internal Sphincter during micturition was formerly considered as an inhibitory action. We now believe that the contraction Of the powerful trigonal muscle passing in the form Of a bow through the weaker arcuate muscles at the vesical orifice helps mechanically to pull open the sphincter. This View is confirmed by endoscopic and cystoscopic studies, as the trigonal muscle is seen to contract and pull open the vesical orifice.Obstruction to urination is generally followed by a partial or com plete compensatory hypertrophy of the trigon. Upon removal Of the obstruction, there is a corresponding compensatory trigonal atrophy. Occasionally following marked obstruction there is an undermining of the trigon, the hypertrophied muscle being dissected away from the bladder wall. Upon contraction it stands up as a ledge dividing the bladder into two parts, mechanically preventing the complete emptying Of the bladder. Furthermore, the contractile force of Such a trigon is not properly applied to expedite the Opening of the vesical orifice. With the removal Of the obstruction by splitting the damlike ledge, the trigon is able to resume its normal functions. However, if there has been a complete removal Of the trigon, micturition is not normal in that the bladder is not completely emptied.About the PublisherForgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.comThis book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully, any imperfections that remain are intentionally left to preserve the state of such historical works.