Figure 4. The mode of action of the ischiocavernosus muscle during erection. (A) The muscle while the penis is flaccid and pointing downward; (B) the muscle while the penis is tumescent and horizontally lying; (C) diagram illustrating the lever action of the contracting ischiocavernosus muscle on the tumescent penis. Muscle contraction effects elevation of the penile shaft to above of the horizontal level.