1298 



THE ORGANS OF DIGESTION 



It is situated in the right iliac fossa, above the outer half of Poupart's ligament; 

 it rests on the Iliopsoas muscle, and lies immediately behind the abdominal wall. 

 As a rule, it is entirely enveloped on all sides by peritoneum, but in a certain number 

 of cases (6 per cent. , according to Berry) the peritoneal covering is not complete, 

 so that a small portion of the upper end of the posterior surface is uncovered and 

 connected to the iliac fossa by connective tissue. The cecum lies quite free in 

 the abdominal cavity and is capable of a considerable amount of movement, 

 so that it may become herniated down the right inguinal canal, and has occasion- 

 ally been found in an inguinal hernia on the left side. 1 



The cecum varies in shape, but, according to Treves, in man it may be classified 

 under one of four types (Fig. 1036). In early fetal life it is short, conical, and 

 broad at the base, with its apex turned upward and inward toward the ileocecal 

 junction. It then resembles the cecum of some of the monkey tribe, e. g., Man- 



gabey monkey. As the fetus grows the 

 cecum increases in length more than in 

 breadth, so that it forms a longer tube than 

 in the primitive form and without the broad 

 base, but with the same inclination inward 

 of the apex toward the ileocecal junction. 

 This form is seen in others of the monkey 

 tribe, e. g., the spider monkey. As develop- 

 ment goes on, the lower part of the tut e 

 ceases to grow and the upper part becomes 

 greatly increased, so that at birth there is a 

 narrow tube, the vermiform appendix, hang- 

 ing 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 ileocecal junction. The three longitudinal 

 bands still start from the base of the appendix, but they are now no longer equi- 

 distant from one another, because the right saccule has grown between the anterior 

 and postero-external 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 been atrophied, so that the original apex of the cecum, with the appendix, 

 is close to the ileocecal junction, and the anterior band courses inward to the 

 same situation. This type is present in about 4 per cent, of cases. 



1 In 310 adult males, Robinson found 8 per cent, with undescended cecum and appendix. Nondescent was 

 found in less than 4 per cent, of females. A partly descended cecum usually lies upon the right kidney. 



FIG. 1035. The cecum and colon laid open to 

 show the ileocecal valve 



