_Reflex Action_ consists of movements and contractions produced by an impression exciting the nerves of the cutis (cutaneous reflex) or tendons (tendinous reflex).
_Cutaneous Reflex Movements_ may be tested by placing the patient in a recumbent position and stroking methodically certain parts of the body, the sole of the foot (plantar reflex), the under side of the knee-joint (popliteal reflex), the abdominal wall (abdominal reflex). Certain reflex movements are of special importance: the cremasteric reflex, on the inner side of the thigh (obtuse in old people and individuals addicted to onanism), the reflex action of the mucous membrane covering the cornea (suspended during stupor, coma, and epileptic convulsions), and the pharyngeal reflex along the isthmus of the fauces (absent in hysterical persons).
The dilatation and contraction of the pupil in accommodation to the distance of the object viewed or in response to light stimuli is undoubtedly the most important cutaneous reflex movement. It may be tested by requesting the patient to look at a distant object and immediately afterwards at the examiner's finger, placed close to his eye, or bringing him suddenly from semi-darkness into the light. If the pupil reacts very slightly to the light, it is called torpid: if it does not react at all, it is called rigid. Rigidity of the pupil always denotes some serious nervous disturbance. In certain diseases, especially tabes, the pupils do not respond to light stimuli, but accommodate themselves to objects.
_Tendinous Reflex Action_ may be tested in every part of the body, but the rotular reflex movement is generally sufficient. The patient is asked to sit on the edge of the bed or on a chair with his legs crossed. If he is healthy, the reflex movement is fairly strong, but in some illnesses spastic movements may be provoked and extend to the abdomen (exaggerated reflex action); in others no reflex is forthcoming. This is one of the first symptoms of tabes.
_Urine_ and _Feces_. As the functions are anomalous, the chemical changes must also be anomalous, owing to the correlation of organs. In born criminals there is a diminished excretion of nitrogen, whereas that of chlorides is normal. The elimination of phosphoric acid is increased, especially when compared with the nitrogen excreted. Pepton is sometimes found in the excretions of paralytic persons in whom there is always an increased elimination of phosphates and calcium carbonate.