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The anal cavity and lower part of the rectum in the fetus. Left figure is four month. Middle figure is six months. Right figure is 9 months. In each the anal canal is distinctly marked off from the rectum proper; the columns of Morgagni and the rectal valves are distinct.

Development of the Anal Cavity

The anal cavity and lower part of the rectum in the fetus. Left figure is four month. Middle figure…

The interior of the anal canal and lower part of the rectum, showing the columns of Morgagni and the anal valves between their lower ends. The columns were more numerous in the specimen than usual.

Interior of the Anal Cavity

The interior of the anal canal and lower part of the rectum, showing the columns of Morgagni and the…