The Elasticity of the Hollow Viscera

The elastic properties of the hollow viscera and muscular tubes differ strikingly in (a) the relaxed and (b) the tonically contracted states, whether tested by distension in response to internal pressure or stretching of strips cut from their walls; in (b) the increments of volume or length progressively rise to a maximum and then diminish, in (a) the maximal effect comes at the beginning of a descending series. While both differ from rubber bands or tubes, the distensibility of (a) differs from that of a rubber tube more strikingly than that of (b). The differences in (a) and (b) are essentially similar to those described by MacWilliam in relaxed and in persistently contracted arteries. The differences are not to be accounted for by overstretching, rupture of fibres, curvature of strips, etc. Similar differences are found under similar conditions in a ribbon of parallel unstriped muscle‐fibre, like the retractor penis, which recovers perfectly and can show spontaneous rhythmic contractions afterwards. There seems to be an essential difference between the elasticity of tonically contracted unstriped muscle and that of skeletal muscle and other animal tissues, as hitherto described. The accepted account of the elasticity of the animal tissues is wholly incorrect as applied to tonically contracted unstriped muscle. Cardiac muscle (frog) apparently resembles unstriped muscle in this respect. The essential peculiarity seems to be related to the tonically contracted condition of unstriped muscle, and not to the same tissue when relaxed or when tested by a series of single stimuli.