No. 3.] UTERUS AND EMBRYO. 429 
§ 20. Origin of decidual cells. — Besides the erroneous hy- 
pothesis of Ercolani, there are three views as to the origin of 
the decidual cells known to me, to wit: 1°, they are modified 
leucocytes (Hennig, Langhans, e¢ a/); 2°, they arise from the 
connective tissue cells of the mucosa (Leopold, 36) ; 3°, they 
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are produced by the epithelium (Overlach, 39). The first view 
is not supported by observation, even by its advocates, and may 
be dismissed. Overlach’s observations certainly favor the third 
view, but inasmuch as he has studied only ome uterus with 
pseudo-menstruation from acute phosphorus poisoning, his the- 
