of supernumerary digits and reversion to some lowly organised
progenitor of man.) There are other cases which come more strictly
under our present head of reversion. Certain structures, regularly
occurring in the lower members of the group to which man belongs,
occasionally make their appearance in him, though not found in the
normal human embryo; or, if normally present in the human embryo, they
become abnormally developed, although in a manner which is normal in
the lower members of the group. These remarks will be rendered clearer
by the following illustrations.
In various mammals the uterus graduates from a double organ with two
distinct orifices and two passages, as in the marsupials, into a single
organ, which is in no way double except from having a slight internal
fold, as in the higher apes and man. The rodents exhibit a perfect
series of gradations between these two extreme states. In all mammals
the uterus is developed from two simple primitive tubes, the inferior
portions of which form the cornua; and it is in the words of Dr. Farre,
by the coalescence of the two cornua at their lower extremities that
the body of the uterus is formed in man; while in those animals in
which no middle portion or body exists, the cornua remain ununited. As
the development of the uterus proceeds, the two cornua become gradually
shorter, until at length they are lost, or, as it were, absorbed into
the body of the uterus. The angles of the uterus are still produced
into cornua, even in animals as high up in the scale as the lower apes
and lemurs.
Now in women, anomalous cases are not very infrequent, in which the
mature uterus is furnished with cornua, or is partially divided into
two organs; and such cases, according to Owen, repeat the grade of
concentrative development, attained by certain rodents. Here perhaps
we have an instance of a simple arrest of embryonic development, with
subsequent growth and perfect functional development; for either side
of the partially double uterus is capable of performing the proper
office of gestation. In other and rarer cases, two distinct uterine
cavities are formed, each having its proper orifice and passage. (39.
See Dr. A. Farre s well-known article in the Cyclopaedia of Anatomy
and Physiology, vol. v. 1859, p. 642. Owen, Anatomy of Vertebrates,
vol. iii. 1868, p. 687. Professor Turner, in Edinburgh Medical
Journal, February, 1865.) No such stage is passed through during the
ordinary development of the embryo; and it is difficult to believe,
47