The sphincter valve between the end sac and the duct in the antennal gland of Gammarus pulex was first described by Vejdovsky (1901) as consisting of “three cells forming a funnel-apparatus surrounded by a ring muscle.” According to this author “one can convince oneself of the muscular cell producing the fibrils of the muscular ring” (p. 382). Zavadsky (1914) confirmed the presence of fibrils, but failed to find a muscular cell apart from the valve cells, and concluded that “the muscle ring appears as a differentiation of the nephridial wall” (p. 97). Recent work by Cannon (1923, 1925, 1926, 1931, 1940) and by Cannon and Manton (1927) indicated that fibrils found in connection with a valve are invariably situated within the valve cells.
Influence of Key-Points of Ring Muscle-Up Execution on Movement Performance: A Translational Perspective from Artistic Gymnastics to Mixed Modality Training Workouts
