Petrissage shares the effects of friction and of tapotement. Pinching produces the same effect as a blow on muscle. A local contraction arises, shown by the thickening of the muscle at the spot pinched, from which waves of muscle contraction may spread in both directions; fibrillary contractions may also arise. In this petrissage has exactly the same effect on the muscles as tapotement (see next page) and may be used for the same reasons. I need not therefore discuss it as a muscle manipulation, which is its ordinary use.

In abdominal massage, in which one kneads accessible parts of the alimentary canal by means of the anterior abdominal wall against the posterior, and which may be regarded as a form of petrissage, one produces the same effects on the muscles of the alimentary canal (see later in this chapter).

But petrissage, like friction, promotes reabsorption. By grasping a portion of the tissues between the fingers, whether it consists of skin and subcutaneous tissue or of these and muscle, and pinching them, by means of this movable pressure one induces retrogressive changes in the inflammatory products, subcutaneous infiltrations (so-called cellulitis), or muscle infiltrations (myositis), and brings about their absorption.