This paper is based on the study of the arterial architecture of 100 appendixes, normal and pathologic, removed from human beings representative of the first to the seventh decades of life, inclusive. The method pursued in the study was originally described by Louis Gross in his work on the blood supply to the heart. This consists, in brief, of the injection of the appendicular artery with a barium sulphategelatin suspension of known viscosity. The injection is accomplished in an apparatus which permits accurate control and standardization of temperature, pressure and other modifying elements. The apparatus consists of a wooden box lined with copper and separated into two chambers, an upper and a lower chamber, by a pan which has an outflow tube connecting it with the outside. In the center of the pan are two openings, nicked to prevent dripping into the lower chamber (fig. 1). Outside the incubator is