In answer to the question, how and when did the race
of dancers originate, it may be said that historical
research indicates that a structural variation or
mutation which occasionally appears in Mus musculus,
and causes those peculiarities of movement which are
known as dancing, has been preserved and accentuated
through selectional breeding by the Chinese and Japanese,
until finally a distinct race of mice which breeds
true to the dance character has been established.
The age of the race is not definitely known, but it
is supposed to have existed for several centuries.
FEEDING, BREEDING, AND DEVELOPMENT OF THE YOUNG
In this chapter I shall report, for the benefit of
those who may wish to know how to take care of dancing
mice, my experience in keeping and breeding the animals,
and my observations concerning the development of
the young. It is commonly stated that the dancer
is extremely delicate, subject to diseases to an unusual
degree and difficult to breed. I have not found
this to be true. At first I failed to get them
to breed, but this was due, as I discovered later,
to the lack of proper food. For three years my
mice have bred frequently and reared almost all of
their young. During one year, after I had learned
how to care for the animals, when the maximum number
under observation at any time was fifty and the total
number for the year about one hundred, I lost two by
disease and one by an accident. I very much doubt
whether I could have done better with any species
of mouse. There can be no doubt, however, that
the dancer is delicate and demands more careful attention
than do most mice. In March, 1907, I lost almost
all of my dancers from what appeared to be an intestinal
trouble, but with this exception I have had remarkably
good luck in breeding and rearing them.
My dancers usually were kept in the type of cage of
which Figure 2 is a photograph.[1] Four of these double
cages, 70 cm. long, 45 cm. wide, and 10 cm. deep in
front, were supported by a frame as is shown in Figure
3. The fact that the covers of these cages cannot
be left open is of practical importance. A similar
type of cage, which I have used to some extent, consists
of a wooden box 30 by 30 cm. by 15 cm. deep, without
any bottom, and with a hinged cover made in part of
1 cm. mesh wire netting. Such a cage may be placed
upon a piece of tin or board, or simply on a newspaper
spread out on a table. The advantage of the loose
bottom is that the box may be lifted off at any time,
and the bottom thoroughly cleansed. I have had
this type of cage constructed in blocks of four so
that a single bottom and cover sufficed for the block.
If the mice are being kept for show or for the observation
of their movements, at least one side of the cages
should be of wire netting, and, as Kishi suggests,
such objects as a wheel, a tower, a tunnel, a bridge,
and a turntable, if placed in the cage, will give
the animals excellent opportunity to exhibit their
capacity for varied forms of activity.
