Visual exploration of the skin capillaries by the Lombard1 method has revealed, in certain diseases, changes in form, size, tonus, flow and reactions to certain stimuli. The study of the skin capillaries in the dermatoses has been reported by Niekau,2 Michael3 and others, in which they have noted certain changes in form and function of these vessels. There is as yet no standard established for capillary morphology in normal persons. Sufficient observations have been reported, however, to distinguish definitely from the normal some of the morphologic, numerical and functional variations in the capillaries observed in certain types of cardiovascular-renal disease, polycythemia, Raynaud's disease and related vasomotor states, shock, and a few of the dermatoses. Many of the variations in morphology are only slight. Changes affecting size and number of functioning capillaries, as pointed out by Krogh,4 are of greater importance. Pathologic classification should be based on quantitative comparative studies with