482 Edwin G. Kirk. 
is the young tela submucosa. The boundary between these two 
layers, while not absolutely sharp, is quite well marked, being 
definable within the limit of one or two cells breadths. 
There is yet no trace of a muscularis mucosae, this first appear- 
ing about 9 or 10 em. at the boundary between lamina propria 
and tela submucosa. It originates through the elongation of 
mesenchyme nuclei to a torpedo shape, and the condensation of 
the protoplasm about each nucleus, as a highly eosinophile sub- 
stance. The primitive syncitial anastomoses are retained, the 
new muscle cells being thus joined inter se by delicate prolonga- 
tions of the finely fibrous stroma.* In some stomachs isolated 
muscle fibres apparently appear somewhat earlier (8-14, 9 cm.) 
At 15-16 em. a definite, fairly compact muscularis mucosae is 
present. The fibres of both coats of the tunica muscularis are 
well defined at 2 cm. 
The diversity of opinion as to the part taken in the inception 
of the glands by unequal mesodermic growth, and as to the nature 
of the first mesodermic irregularities, is partially referable, no 
doubt, to differences in the forms used, but there has often been 
the lack of a definite criterion of distinction between such up- 
growths as simply minister to an increase of surface, and such as 
have a definite réle in glandular development. By reference to 
the adult structure, it is seen that only such mesodermic eleva- 
tions can have taken an active part in adenogenesis as are constituted 
by local thickenings of the lamina propria alone. At 2 em. the 
later is of uniform thickness throughout, the basement membrane 
presenting no irregularities of contour, and the epithelium being 
everywhere of the same height. But the tela submucosa has 
thickened in linear ridges, so as to produce folds or rugae, several 
of which run almost the length of the stomach. 
The epithelium is a single layer of high columnar cells, as shown 
in fig. 1 of the 6 em. stage The nuclei are arranged in several 
rows; this, in connection with the small diameter of the cells, 
readily gives rise, in even slightly oblique sections, to a stratified 
3’ This confirms MeGill, 1907. 
