In a previous communication by one of us1 and in the excellent studies of Müller,2 Jaensch3 and others, it has been shown that the cutaneous capillaries reach the mature form of development between the ages of 6 months and 1 year. After this time the morphologic structure of the capillaries remains constant, though the loops may lengthen and become wider in caliber during the advancing years. It has also been shown by Doxiades and Pototzky,4 Jaensch,5 Hoepfner,6 Powdermaker7 and others that the capillaries in persons with mongolism do not develop normally. They are markedly delayed in growth and rarely reach normal, mature forms. Occasionally one finds normal capillaries (Pototzky,8 Karger9), but this is rare. Instead, one finds all sorts of bizarre capillary patterns, and many of the primitive characteristics of the capillaries, such as the subpapillary plexus, undifferentiated venous and arterial