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[N. 8. Vol. XL VII. No. 1224
tion of the magnesium sulphate is completed
by washing the crystals with very dilute al-
cohol, after which they may be immediately
used for further precipitation.
In the complete paper the authors will dis-
cuss in some detail the application of this
method to the quantitative determination of
pectin in the laboratory or in commercial jelly-
making establishments. It is considered es-
pecially desirable at this time to point out that
precipitation by magnesium sulphate may ad-
vantageously supplant the use of alcohol in
the household test for pectin. "While alcohol
is not ordinarily available to the housewife,
Epsom salts are to be found in every home and
in almost every grocery store. By heating a
small quantity of the aqueous extract of fruit,
dissolving Epsom salts therein, and observing
the amount of pectin thrown out of solution,
one obtains an accurate measure of the pectin
content of the fruit and is thereby enabled to
form a judgment as to the amount of sugar
necessary to form a jelly.
Discussion of many details of technique and
of certain applications of the method here
presented in outline are necessarily reserved
for presentation in the full paper immediately
forthcoming in the journal already named.
C. A. Magoon,
Joseph S. Caldwell
Office Horticultural and
Bureau of Plant Industry,
Washington, D. C.
THE CARE AND BREEDING OF ALBINO RATS
At this time when the government is using
great numbers of albino rats and mice for
inoculation purposes, numerous letters have
been received from various sources asking for
information regarding a source of supply and
the care and breeding of these animals. This
demand is so widespread that it is deemed
most expedient to give this information in a
simple form and to disseminate it to the
greatest number of people by publishing it in
this journal. In so doing those persons who
are anxious to do their bit in this present
crisis and who reside sufficiently near base
hospitals and cantonments may be able to rear
and supply these animals.
Albino rats and mice are exceedingly easy
to raise. Their care and feed are practically
the same and the cages in which they are kept
can be identical. The cages for mice can,
however, be much smaller. Our colony at the
present time consists wholly of rats and the
following applies strictly to them. It in gen-
eral applies to mice also. These animals can
ordinarily be handled by the bare hands with-
out any danger of being bitten. Occasionally,
however, a mother with young may be less
docile if her young are disturbed. In such
cases the use of a pair of heavy gloves is ad-
visable. The oftener the rats are handled and
petted the less likely they are to bite.
The cages in which our rats are kept and
which we have found most satisfactory are
made of one-fourth-inch galvanized wire net-
ting with all the comers, edges and doors
bound, or reenforced by galvanized iron (Fig.
1). They are made 12 inches high, 18 inches
wide and 24 inches long. A partition of
woven galvanized wire, provided with a sliding
door (D4in. X^in.), divides this into two
compartments 12 in. X 12 in. X 18 i n - Each of
these compartments is provided with a woven
wire door (D, 6 in. X 6 in.) which slides up in
runners made of galvanized iron (Rn). These
doors are of ample dimensions to enable one to
easily reach into all parts of the cage.
The bottom is separate and composed of
galvanized iron 20 in. X 25 in. with three of
the sides turned up 1 in. The front side is
left flat to facilitate cleaning. The cage thus
sits in this bottom and can be readily lifted off
when cleaned. This process, which should be
attended to at least once in two weeks, can be
accomplished without handling the rats or
without danger of their leaving the compart-
ments to which they belong. This is done by
placing the whole cage on a broad table, lifting
the top about one half an inch and carrying it
along to the bare table. The rats are thus
forced along with the cage and the bottom left
free. The old sawdust and excelsior used for
bedding are now scraped out and a fresh sup-
ply added. The cage containing the rats in
June 14, 1918]
their proper compartments is now replaced in
the same manner that it was removed.
Clean fresh water is constantly supplied by
means of- an inverted bottle (B) provided with
an air-tight rubber st6pper (R) and glass tube
5 mm. in diameter ((■?). The spring clips (0)
permit ready removal of the bottles for filling.
The bottles are supported at the lower end on
two bent wire nails (8) between which the
glass tube passes (Figs. 1 and 3). We have
found bottles containing eight ounces the most
serviceable, as they are not too large and do
not need refilling very often.
The albino rat is omnivorous in its diet and
will devour almost anything a man will eat.
They should be fed once each day. The food
consists of cracked corn daily, such table
scraps as are available, green stuff, such as
lettuce, cabbage, etc. Where a large number
of rats are being reared it is advisable to
procure the refuse from a restaurant or hotel.
Table scraps give a fairly balanced diet and
Fig. 1. Perspective drawing of the woven- wire partition dividing the two compartments; D 6 in.
portion of the cage showing the dimensions and , x 6 in., sliding doors into cages; G, glass drinking
plan of construction. tube from water-bottle; L, lifts for sliding doors;
B, drinking bottle; C, spring clips for holding B > rubber ^PP^ Sn > galvanized-iron runs for
bottle; Cg, cage; D 4 in. X 4 in., sliding door in slidin g doors 5 S > supports for bottle.
Fig. 2. Galvanized iron bottom, giving dimensions showing the support of the bottle, 8, and the man-
and plan of construction. ner in which the tube leads into the eage.
Fig. 3. Sectional view of drinking fountain
[N. S. Vol. XLVII. No. 1224
we have had excellent success with this food.
If table scraps are not available, cooked beans.
nuts and meat two or three times per week
should be provided. The amount of food
given should always be greater than will be
consumed if one is desirous of quick returns.
When rats are fed on a sufficient quantity of a
well-balanced ration they are very prolific and
A pair should be placed in each compart-
ment. The female comes in heat about every
five days and the period of gestation is ap-
proximately 21 days. The period of gestation
is prolonged a few days if the female is nurs-
ing a litter of young during this time. Nu-
merous instances are on record where mating
has occurred the same day that young were
The number of young in a litter varies from
one to fifteen, the average number being about
six or eight. They grow rapidly and can be
weaned at 30 or 35 days of age. If one de-
sires to maintain a pure breed the young
should never be allowed to remain with the
parents after they have reached the age of
fifty days, as breeding is likely to occur. A
litter should always be weaned regardless of
age as soon as (preferably just before) a new
litter is born to prevent starvation of the new-
born. In case the weaned litter is very young
(25 to 35 days) milk should be added to their
diet. To prevent inbreeding the sexes should
be separated at weaning and confined in sepa-
rate cages. With proper food, however, in-
breeding can go on without apparent detriment
for a number of generations.
The sexes in the young may be distinguished
by the following characteristics:
The males may be recognized by a greater
distance between the anus and the genital
In the male the genital papilla is larger
than in the female.
At about 15 days of age the nipples are
visible in the female.
After the hair covers the body a strip ex-
tending from the anus to the genital papilla
remains almost bare in the female, while in the
male this region is covered with hair except a
small area immediately below the anus which
later becomes the scrotum.
After the descent of the testes into the
scrotum the males can readily be distin-
The age at which the young females become
sexually mature varies between rather wide
limits, but usually between 70 and 90 days.
The earliest age at which we have found them
sexually mature is 69 days. Lantz 1 records
a case of sexual maturity at the early age
of 35 days and Jackson 2 one at 49 days. Sexual
activity in the females may continue until
they have reached the age of 600 days. We
have not determined the ages at which sexual
activity begins and ceases in the male.
A great difference is noticed in the ability
of females to produce young. Some appear to
be sterile, while others have given birth to as
many as nine litters. If one is desirous of
securing numbers, the offspring from prolific
breeders should be selected for breeding.
The rats do best in a well-ventilated room
of fairly uniform temperature. Extreme tem-
perature should be avoided.
Since these animals need daily attention
they can not be shipped long distances unless
provision is made for watering and feeding
them en route. Our available supply is quite
limited but we can generally furnish a few
pairs to any one within shipping distance who
is willing and able to breed rats for purposes
of supplying the government, or for general
The three main items for success are clean-
liness, a sufficient quantity of a balanced
ration, and avoidance of great changes in
temperature. With these carefully looked
after success is assured.
J. E. Slonakek
Physiological Laboratoeies of
i David E. Lantz, ' ' Natural History of the Eat, ' '
In "The Eat and its Eelation to the Public
Health," by various authors. P. H. and M. H.
Service, Washington, 1910.
2 C. M. Jackson, ' ' On the Eeeognition of Sex
through External Characters in the Young Eat,"
Biological Bulletin, Vol. XXIII., No. 3, August,