During the past few years much information has accumulated concerning the physiological and pathological significance of tissue mast cells. It is more than of historical interest to note that these cells were first clearly described by Ehrlich in 1878.1Their abundance in connective tissue which he considered to be "well-nourished," as observed with chronic inflammation, prompted the designation "Mastzellen" (well-fed cells). Ehrlich also proposed that the granules of the mast cells, which exhibit a strong affinity for basic dyes and the property of altering the original color of the dye (metachromasia), represented nutrient for the connective tissue. In the light of this hypothesis, as well as the great interest recently demonstrated in the connective tissue and its purported disorders, it is not surprising to learn that the mast cells have been considered to play a significant role in fibrillogenesis, particularly in the elaboration of connective tissue matrix or ground