548 Franklin P. Johnson. 
Some of these are more elongated than the thickenings found above 
and form slight irregular ridges. These ridges have as yet no 
corresponding depressions of the mesenchyma. Below this, 
there is a diminution in the size of the intestine, and the ridges— 
2—4 in number—are irregular and changeable in position. Before 
the large intestine is reached, the ridges are lost and the lumen 
of the small intestine assumes a more rounded appearance. 
The vacuoles have entirely disappeared from the epithelium 
of the duodenum at 30 mm. and the lumen is pervious throughout. 
The villi are even more numerous than at 24 mm. and vary in 
size, the tallest now measuring about .211 mm. The diameters of 
their bases vary within the limits of .089 and .146 mm. The villi 
are very irregular in shape, some flattened at their bases, others 
rounded. The arrangement of villi in rows is more pronounced 
than at 24mm. Additional villi have developed either in between 
the villi of the rows already present, or by forming additional 
rows. In some places the rows of villi have the appearance of 
irregular longitudinal folds, suggesting a fusion of adjacent villi. 
This apearance is perhaps due to the rapid development of new 
villi between the older ones. 
In the jejunum at this stage a similar arrangement of villi is 
found, but in its lower part the developing villi are further sepa- 
rated.. Following down the ileum, they become smaller and 
smaller. Then comes a region in which there are only a very few 
villi and thickenings, these being more scattered than before. 
Following this, there is a region in which the diameter of the tube 
diminishes, and in this portion longitudinal folds are present. 
Further down it widens out again and the folds are lost; this is 
followed by another diminution. Several of these narrowed places 
are found in this part of the small intestine, and between them the 
tube regains its former diameter. In the narrowed portions, rather 
irregular folds are found, varying from 2 to 4 in number. In the 
widened portions, very young villi are present, but no folds. 
Fig. 20 is of a wax reconstruction of a portion of the epithelium 
at a place where there is a diminution in the diameter of the ileum. 
In the widened portion, the beginnings of a few villi are seen; 
