Rectum and Anal Canal in Fetus
The anal canal and rectum in a fetus. A, aged 4 to 5 months; B, 6 moths; C, 9 months. In each he anal canal is distinctly marked off from the rectum proper; the column of Morgagni and the rectal valve are distinct.
Cunningham, D.J. Textbook of Anatomy (New York, NY: William Wood and Co., 1903)