THE REGULAR OCCURRENCE OF INTESTINAL DIVER- 
TICULA IN EMBRYOS OF THE PIG, RABBIT, AND MAN. 
BY 
FREDERIC T. LEWIS, M.D., anp FRED. W. THYNG, PH. D. 
From the Department of Comparative Anatomy, Harvard Medical School. 
WITH 5 TEXT FIGURES. 
While engaged in the study of a human embryo of 13.6 mm., one of 
the writers (Dr. Thyng) discovered a knob-like outpocketing of the intes- 
tinal epithelium, a short distance beyond the pancreas. This was thought 
to be an accessory pancreas, and was reported at the twenty-first session 
of the Association of American Anatomists as “a possible posterior pan- 
creas in mammalian embryos.” The other writer, five years before, had 
made reconstructions of a similar structure found in several rabbit em- 
bryos. Together we undertook the further investigation of these knobs 
or pockets with the following results. 
Pia Embryos. 
The youngest pig embryos examined measured 5.5 mm. In one of 
these, as shown in the reconstruction Fig. 1, the intestinal epithelium 
presents a round knob, just below the dorsal pancreas. The knob, Div., 
is shown in section in Fig. 3 A. It contains no lumen; there are no 
mitotic figures among its nuclei. The intestine of this embryo showed 
only a single diverticulum, but in another pig of 5.5 mm. two were found, 
as shown in Fig. 2. 
Three pigs of 6.0 mm. were examined. ‘Two of these (H. EH. C. 918 
and 919) each present a single round knob with constricted pedicle; the 
other (H. E. C. 9) has two diverticula. A mitotic figure is found at the 
neck of one of the knobs and at the base of another. For a given number 
of cells it appears that mitoses are more frequent in the knobs than in 
the surface epithelium, yet from these and other specimens it is evident 
that mitoses are not confined to the diverticula. 
In a 7.0-mm. embryo (H. E. C. 11) two diverticula were found. The 
anterior of these is merely a hemispherical bulging of the epithelium; 
the posterior has a constricted neck and is closely applied to the endo- 
AMERICAN JOURNAL OF ANATOMY.—VOL. VII. 
