en too many and
great to allow this one to weigh in an adequate degree; while, during
the greater portion of the period, choice on the part of women has
scarcely operated: in earlier times they were stolen or bought, and in
later times mostly coerced by parents. Thus, reconsideration of the
facts does not show me the invalidity of the conclusion drawn, that this
decrease in size of jaw can have had no other cause than continued
inheritance of those diminutions consequent on diminutions of function,
implied by the use of selected and well-prepared food. Here, however, my
chief purpose is to add an instance showing, even more clearly, the
connexion between change of function and change of structure. This
instance, allied in nature to the other, is presented by those
varieties, or rather sub-varieties, of dogs, which, having been
household pets, and habitually fed on soft food, have not been called on
to use their jaws in tearing and crunching, and have been but rarely
allowed to use them in catching prey and in fighting. No inference can
be drawn from the sizes of the jaws themselves, which, in these dogs,
have probably been shortened mainly by selection. To get direct proof of
the decrease of the muscles concerned in closing the jaws or biting,
would require a series of observations very difficult to make. But it is
not difficult to get indirect proof of this decrease by looking at the
bony structures with which these muscles are connected. Examination of
the skulls of sundry indoor dogs contained in the Museum of the College
of Surgeons, proves the relative smallness of such parts. The only
pug-dog's skull is that of an individual not perfectly adult; and though
its traits are quite to the point they cannot with safety be taken as
evidence. The skull of a toy-terrier has much restricted areas of
insertion for the temporal muscles; has weak zygomatic arches; and has
extremely small attachments for the masseter muscles. Still more
significant is the evidence furnished by the skull of a King Charles's
spaniel, which, if we allow three years to a generation, and bear in
mind that the variety must have existed before Charles the Second's
reign, we may assume belongs to something approaching to the hundredth
generation of these household pets. The relative breadth between the
outer surfaces of the zygomatic arches is conspicuously small; the
narrowness of the temporal fossae is also striking; the zygomata are very
slender; the