Heredity seems to be a factor, and duplex uteruses predispose to multiple births.

Ross reports an instance of double uterus with triple pregnancy.
Quadruplets are supposed to occur once in about every 400,000 births.
There are 72 instances recorded in the Index Catalogue of the Surgeon General's Library, U.S.A., up to the time of compilation, not including the subsequent cases in the Index Medicus.

At the Hotel-Dieu, in Paris, in 108,000 births, covering a period of sixty years, mostly in the last century, there was only one case of quadruplets.

The following extract of an account of the birth of quadruplets is given by Dr.De Leon of Ingersoll, Texas:-- "I was called to see Mrs.E.T.Page, January 10, 1890, about 4 o'clock A.M.; found her in labor and at full time, although she assured me that her 'time' was six weeks ahead.

At 8 o'clock A.M.