Or 
ey | 
Mucous Membrane in the Human Embryo. Di: 
TABLE 4 
EPITHELIUM OF SMALL ImTEsTINE (Mrp Rearon) 
THICKNESS! OF DIAMETER OF 
EMBRYO SURFAGH EPITHELIUM EPITHELIAL VILLI INTESTINAL GLANDS 
TUBE 
; j 2 Diameter® 
Length In Cell Taek? Tagen Height? (at bases) Length‘ Diameter? 
In mm. Layers in mm. in mm. in mm. in mm. 
lee 2-3 .024 .052 
16 2 024 101 
19 3-4 .052 141 
22.8 3-5 052 . 158 
24 1 024 135 12 sill 
30 ? t 28 18 ll 
37 1 024 39 .20 14 
42 1 .021 44 .18 as 
55 1 020 io .26 males .036 .06 
73 1 .019 1.09 100 15 .048 06 
91 1 .024 1.28 of 14 .050 .06 
120 1 015 1.40 56 ll .060 .06 
134 1 015 2) .63 sal - .065 06 
187 1 015 Zo .70 alin .088 .06 
240, 1 .012 one .70 07 10 04 
Birth 1 .012 4.9 .70 sil 12 04 
1 On top of villi when present. 
2 Tallest. 
3 Average of a number of measurements. 
4 Longest. 
CONCLUSIONS 
(E'sophagus 
1. The cesophagus is at first a simple epithelial tube, the 
walls of which contain three or four rows of nuclei. 
2. In embryos of about 20 mm., vacuoles form in the epithe- 
lium but the lumen remains pervious throughout. These vacuoles 
disappear by breaking into the lumen. This causes the epithelium 
to become thinner and the lumen to increase in size. The cause of 
the formation of vacuoles has not yet been determined. 
3. Longitudinal folds of the mucosa are constant structures 
in the cesophagus. In the upper third of the cesophagus the folds 
are irregular and variable. In the middle and lower thirds there 
