268 PROF. OWEN ON THE ANATOMY 
of the mesentery, whence it descends to form a fifth long loop, situated at the left side 
of the abdomen, behind the others, and then becoming looser, after a short convolution, 
terminates in the rectum. The ceca in one specimen measured each five, in another 
six inches in length ; they are attached to the last folds of the ilewn: their tunics are 
thinner than those of the rest of the alimentary canal. The adipose processes developed 
beneath the peritoneum investing the ileum and ceca, are smaller and more detached 
than those connected with the preceding intestinal loops, and assume the appearance of 
‘‘ appendices epiploice’.” 
In one Apteryx I found a very short cecum,—the remnant of the ductus vitello-intes- 
tinalis,—attached to about the middle of the small intestine*; and in the viscera of the 
small female Apteryx transmitted to me by Dr. Logan, there extended from the same 
relative position of the intestinal tube an obliterated duct three lines in length, which 
expanded into a still persistent vitelline sac of a subglobular form, about an inch in 
diameter, but collapsed and with wrinkled parietes. These presented a moderate degree 
of thickness in the moiety of the sac next the duct, but became gradually thinner to 
the opposite side. The interior of the sac was lined with a stratum of a yellowish sub- 
stance resembling adipocere, and contained many small wavy filamentary vessels, con- 
verging to the commencement of the duct, and evidently remains of the vasa lutea. A 
small branch from the mesenteric artery, the remnant of the omphalo-mesenteric, and 
a minute corresponding vein, accompanied the pedicle of the sac (PI. LI. fig. 1, s, ¢.). 
In the large male Apteryx the intestinal canal measured four feet, independently of 
the ceca, which were each six inches in length: the rectum was four inches long. 
The general diameter of the small intestines in the specimen first dissected was 
three lines; in the male Apteryx with the full stomach their diameter was five lines: 
they slightly diminish in size as they approach the rectum. In the duodenum the 
mucous membrane is beset with extremely fine villi, about one line in length ; towards 
the end of the duodenum these villi are converted into thin zigzag longitudinal 
1 These processes and the return of the small intestine, in the latter part of its course, to the duodenum and 
root of the mesentery, give to the part continued thence to the rectum the characters of the colon in Mam- 
malia. The learned Editor of the excellent edition of Cuvier’s Lecons d’ Anatomie Comparée, now in course of 
publication, is disposed to consider all that part of the small intestine which intervenes between the single 
vitelline cecum (in those birds which have it) and the double ordinary ceca, as representing the colon: and 
the analogy of the colon of the Hyraz, which is similarly bounded at its commencement by a single cecum, and 
at its termination by a double one, is undoubtedly very close. If, however, we are guided by the analogies 
afforded by the other oviparous classes, with which birds present so close a conformity of general structure, and 
in which the colon is always short, wide, generally straight, and in some, as Python, Testudo, Iguana, marked 
off, or commencing by a single cecum, as in Mammalia, there can be no question in that case but that the part 
of the intestinal canal in Birds corresponding to the colon of Reptiles, is that which succeeds the entry of the 
two ceca, and which, from its shortness and straightness, is usually called the rectum. In the Ostrich, how- 
ever, it is long and convoluted, and is provided with transverse valvule conniventes. A similar structure in a 
less degree is present in the colon of the Iguana. 
2 Pl, L. d. 
