538 Franklin P. Johnson. 
The growth of the mucous membrane of the stomach is per- 
haps best shown in table 2. From the earliest stage up to 42 mm. 
there is but a slight increase in the thickness of the epithelial 
wall. At 16 mm. the pits begin to form, and rapidly increase in 
number and in size. At 55 mm., due to the presence of pits on 
the inner surface and alternating grooves on the outer (mesen- 
chymal) surface, as described above, the epithelium becomes 
reduced to a single layer of low cells. When measured as in the 
preceding stages, the epithelium averages .057 mm. in thickness. 
When determined as in the following stages, 7.e., the epithelium 
which surrounds the individual pit, it measures .012 mm. Thus 
by the readjustment of the cells which is completed at this stage, 
the epithelium is reduced in thickness from .057 mm. to .012 mm. 
At 91 mm. the surface epithelium is much thicker because of 
the extremely long basal processes of its cells. At 120 mm. 
the basal processes are shorter, but from this stage up to birth 
there is a gradual increase in the thickness of the epithelium. 
The gastric pits rapidly increase in depth but there is a more 
gradual and variable increase in their width and the distance 
between adjacent pits. The glands also increase rapidly in length, 
but slowly in diameter. | 
Folds. Folds of the mucous membrane of the stomach are more 
variable in number than in the cesophagus. In an embryo of 10 
mm. the epithelial wall of the stomach is perfectly smooth through- 
out. At 16 mm. there are two or three slight folds on the side of 
the greater curvature, and indications of about the same number 
of the side of the lesser curvature. At 19 mm. there are 2-3 
large longitudinal folds on the side of the greater curvature, while 
the opposite wall is rounded, with no indications of folds. At 
22.8 mm. there are 7-10 folds, including both walls; at 42 mm. 
10-12; at 55 mm. about the same number but they are not as 
high. At 120 mm. and 187 mm. large folds are found, while at 
240 mm. and at birth the folds are very much higher. In the last 
four cases, the number of the folds was not obtained. J’rom these 
and other observations it would seem that the folds are rather 
inconstant structures, their number and size depending on the 
state of contraction of the muscular walls. Brand (77) found 
