Henry Gray (18251861). Anatomy of the Human Body. 1918.
part becomes greatly increased, so that at birth there is a narrow tube, the vermiform process, hanging from a conical projection, the cecum. This is the infantile form, and as it persists throughout life in about 2 per cent. of cases, it is regarded by Treves as the first of his four types of human ceca. The cecum is conical and the appendix rises from its apex. The three longitudinal bands start from the appendix and are equidistant from each other. In the second type, the conical cecum has become quadrate by the growing out of a saccule on either side of the anterior longitudinal band. These saccules are of equal size, and the appendix arises from between them, instead of from the apex of a cone. This type is found in about 3 per cent. of cases. The third type is the normal type of man. Here the two saccules, which in the second type were uniform, have grown at unequal rates: the right with greater rapidity than the left. In consequence of this an apparently new apex has been formed by the growing downward of the right saccule, and the original apex, with the appendix attached, is pushed over to the left toward the ileocolic junction. The three longitudinal bands still start from the base of the vermiform process, but they are now no longer equidistant from each other, because the right saccule has grown between the anterior and posterolateral bands, pushing them over to the left. This type occurs in about 90 per cent. of cases. The fourth type is merely an exaggerated condition of the third; the right saccule is still larger, and at the same time the left saccule has become atrophied, so that the original apex of the cecum, with the vermiform process, is close to the ileocolic junction, and the anterior band courses medialward to the same situation. This type is present in about 4 per cent. of cases.
The Vermiform Process or Appendix (processus vermiformis) (Fig. 1073) is a long, narrow, worm-shaped tube, which starts from what was originally the apex of the cecum, and may pass in one of several directions: upward behind the cecum; to the left behind the ileum and mesentery; or downward into the lesser pelvis. It varies from 2 to 20 cm. in length, its average being about 8.3 cm. It is retained in position by a fold of peritoneum (mesenteriole), derived from the left leaf of