In some instances, together with great increase of tendon reflex, we observe a transfer of the centrifugal impulse to other nerves of the same extremity, or across the spinal cord to nerves and muscles of the homologous limb. Another interesting manifestation of morbid reflex movements is the defensive tonic spasm of muscles about a diseased joint (of the hip-muscles in coxitis, of vertebral muscles in Potts' disease). This constitutes a valuable symptom for the differential diagnosis between articular and neural diseases in certain cases. Clinically, increase of reflex action is not as valuable an indication as its absence, many healthy persons having high reflexes. Still, when studied comparatively as to topography (comparing the two sides of the body) and as to variations at different times in a given case, the symptom is of considerable assistance. IV. Trophic Symptoms. Our present knowledge of this great group of symptoms of nervous disease is in a somewhat chaotic state; and although we possess a large accumulation of facts of this category, their classification is incomplete and their explanation is for the most part theoretical and unsatisfactory. The following subdivisions may be made to include all the phenomena, and is sufficient for clinical purposes: 1. DEGENERATIVE ATROPHY, as distinguished from the simple atrophy of insufficient nutrition, of disuse of the parts, and of retarded growth, includes all those trophic symptoms in which, under the influence of nervous disease, the solid tissues exhibit histological and chemical alterations as well as reduction of volume. The principal factor of this group is—