Two instances of this variation are shown in Figs. 535 and 536, taken from preparations in the Morphological Museum of Columbia University. In both careful examination of the external as well as of the mucous surface of the cæcum demonstrated the entire absence of the appendix, and the subjects from which they were obtained presented no scars or other evidences of operative removal or of pathological processes. They are both, therefore, authentic instances of complete congenital absence of the appendix, not of so-called retro-peritoneal or hidden appendix.[13]
The two examples differ from each other in some details. In the first case (Fig. 535, schema, [Fig. 509], IIIa) the cæcum is rounded and globular. The ventral longitudinal muscular band is vertical and continued to the lowest point of the pouch, which greatly resembles the cæcum of a typical cynomorphous monkey.
In the second case (Fig. 536, schema, [Fig. 509], IIIb) the cæcum turns upwards and to the left, terminating in a sharp point, to which several lobes of epiploic fat are attached.
We must assume that in these cases the embryonic portion of the cæcal bud was developed just sufficiently to yield the required adult pouch with nothing to spare, so to speak, which could remain rudimentary in the form of an appendix.
Instances of exceedingly rudimentary and reduced appendix are also encountered.
In the case illustrated in Fig. 537 the appendix formed a small conical elevation without distinct lumen, measuring only 0.5 cm. in length.
Fig. 537.—Human adult. Ileo-colic junction and cæcum, with rudimentary appendix. (Columbia University Museum, No. 1655.)
B. Position and Peritoneal Relations of the Appendix.—Statistical records of the position of the appendix indicate a wide range of variation. In general the results obtained by different observers show that certain positions of the appendix are encountered in a sufficiently large percentage of the cases to enable us to adopt a classification, but that a very extensive series of records are required in order to determine even approximately the preponderant relations of the appendix. The following are the most frequently observed positions:
1. The appendix is directed upward, inward and to the left, the terminal portion being frequently coiled under cover of the ileum and mesentery. This position of the appendix is largely due to the normal crescentic curve of the cæcum, which carries the apex of the pouch and the root of the appendix upward and to the left. Its production is, moreover, favored by the tendency of the adult cæcum to develop by dilatation of the ventral and right wall at the expense of the left side of the pouch, thus relatively shortening the interval between the origin of the appendix and the ileo-colic junction.