Before skinning, the bird should be measured. With a metric-system measure carefully take the alar extent, i.e. spread from tip to tip of outstretched wings; length of wing, i.e. length from wrist-joint to tip; length of bill in straight line from base (on dorsal aspect) to tip; length of tarsus, and length of middle toe and claw.
To skin the bird, cut from a.n.u.s to point of breast-bone through the skin only. Work skin away on each side to legs; push each leg up, cut off at knee-joint, skin down to next joint, remove all flesh from bone, and pull leg back into place; loosen skin at base of tail, cut through vertebral column at last joint, being careful not to cut through bases of tail-feathers; work skin forward, turning it inside out, loosening it carefully all around, without stretching, to wings; cut off wings at elbow-joint, skin down to next joint and remove flesh from wing-bones; push skin forward to base of skull, and if skull is not too large (it is in ducks, woodp.e.c.k.e.rs, and some other birds), on over it to ears and eyes; be very careful in loosening the membrane of ears and in cutting nict.i.tating membrane of eyes; do not cut into eyeball; remove eyeb.a.l.l.s without breaking; cut off base of skull, and scoop out brain; remove flesh from skull, and "poison" the skin by dusting it thoroughly with the powdered a.r.s.enic and alum mixture. Turn skin right side out, and clean off fresh blood-stains by soaking them up with corn-meal; wash off dried blood with water, and dry with corn-meal. Corn-meal may be used during skinning to soak up blood and grease.
There remains to stuff the skin. Fill orbits of eyes with cotton (this can be advantageously done before skin is reversed); thrust into neck a moderately compact, elastic, smooth roll of cotton about thickness of the natural neck; make a loose oval ball of size and general shape of bird's body and put into body-cavity with anterior end under the posterior end of neck-roll; pull two edges of abdominal incision together over the cotton, fasten, if necessary, with a single st.i.tch of thread, smooth feathers, fold wings in natural position, wrap skin, not tightly, in thin sheet of cotton (opportunity for delicate handling here) and put away in a drawer or box to dry. Before putting away tie label to leg, giving date and locality of capture, s.e.x and measurements of bird, and name of collector. Before bird is put into permanent collection it should be labelled with its common and scientific name.
The mounting of birds in lifelike shape and att.i.tude is hard to do successfully; and a collection of mounted birds demands much more room and more expensive cabinets than one of skins. For instructions for the mounting of birds see Davie's "Methods in the Art of Taxidermy," pp. 39-57; or Hornaday's "Taxidermy and Zoological Collecting." For a more detailed account of making bird-skins, see also these books, or Ridgway's "Directions for Collecting Birds."
In collecting birds' nests cut off the branch or branches on which the nest is placed a few inches above and below the nest, leaving it in its natural position. Ground-nests should have the section of the sod on which they are placed taken up and preserved with them. If the inner lining of the nest consists of feathers or fur put in a "moth-ball" (naphthaline).
To preserve birds' eggs they should be emptied through a single small hole on one side by blowing. p.r.i.c.k a hole with a needle and enlarge with an egg-drill (obtain of dealers in naturalists' supplies, see p. 453.) Blow with a simple bent blowpipe with point smaller than the hole. After removing contents clean by blowing in a little water, and blowing it out again. After cleaning, place the egg, hole downward, on a layer of corn-meal to dry. Label each egg by writing on it near the hole a number. Use a soft pencil for writing. This number should refer to a record (book) under similar number, or to an "egg-blank," containing the following data: name of bird, number of eggs in set, date and locality, name of collector, and any special information about the eggs or nest which the collector may think advisable. The eggs may be kept in drawers or boxes lined with cotton, and divided into little compartments.
For detailed directions for collecting and preserving birds' eggs and nests, see Bendire's "Directions for Collecting, Preparing, and Preserving Birds' Eggs and Nests" or Davie's "Methods in the Art of Taxidermy," pp. 74-78.  _Mammals._--Any mammal intended for a scientific specimen should be measured in the flesh, before skinning, and as soon after death as practicable, when the muscles are still flexible. (This is particularly true of larger species, such as foxes, wildcats, etc.) The measurements are taken in millimetres, a rule or steel tape being used. (1) Total length: stretch the animal on its back along the rule or tape and measure from the tip of the nose (head extended as far as possible) to the tip of the fleshy part of tail (not to end of hairs). (2) Tail: bend tail at right angles from body backward and place end of ruler in the angle, holding the tail taut against the ruler. Measure only to tip of flesh (make this measurement with a pair of dividers). (3) Hind foot: place sole of foot flat on ruler and measure from heel to tip of longest toe-nail (in certain small mammals it is necessary to use dividers for accuracy). The measurements should be entered on the label, along with such necessary data as s.e.x, locality, date, and collector's name.
Skin a mammal as soon after death as possible. Lay mammal on back and with scissors or scalpel open the skin along belly from about midway between fore and hind legs to vent, taking care not to cut muscles of abdomen. Skin down on either side of the body by working the skin from flesh with fingers till hind legs appear. Use corn-meal to stanch blood or moisture. With left hand grasp a leg and work the knee from without into the opening just made; cut the bone at the knee, skin leg to heel and clean meat off the bone (leaving it attached of course to foot). In animals larger than squirrels skin down to tips of toes. Do the same with other leg. Skin around base of tail till the skin is free all around so that a grip can be secured on body; then with thumb and forefinger hold the skin tight at base of tail and slowly pull out the tail. In small mammals this can be done readily, but in foxes it is often necessary to split the skin up along the under side and dissect it off the tail-bones. After the tail is free skin down the body, using the fingers (except in large mammals) till the fore legs are reached; treat the fore legs in the same manner as hind legs, thrusting elbow out of the skin much as a person would do in taking off a coat; cut bone at elbow; clean fore-arm bone. Skin over neck to base of ears. With scalpel cut through ears close to skull. With scalpel dissect off skin over the head (taking care not to injure eyelids) down to tip of nose, severing its cartilage and hence freeing skin from body. Sew mouth by pa.s.sing needle through under lip and then across through two sides of the upper lip; draw taut and tie thread.
Poison skin thoroughly. Turn skin right side out. Next sever the skull carefully from body, just where the last neck-vertebra joins the back of the skull. It is necessary to keep the skull, because characters of bone and teeth are much used in cla.s.sification. Remove superfluous meat from the skull and take out brain with a little spoon made of a piece of wire with loop at end. Tag the skull with a number corresponding to that on skin, and hang up to dry. A finished specimen skull is made by boiling it a short time and picking the meat off with forceps, further cleaning it with an old tooth-brush, when it is placed in the sun to bleach. Care must be taken always not to injure bones or dislodge teeth.
Mammals are stuffed with cotton or tow; the latter is used in species from a gray squirrel up. Large mammals stuffed with cotton do not dry readily, and often spoil. Being much thicker-skinned than birds, mammals require more care in drying and ordinarily require a much longer period. Soft hay may be subst.i.tuted for tow; never use feathers or hair. Roll a longish wad of cotton about the size of body and insert with forceps, taking care to form the head nearly as in life.
Split the back end of the cotton and stuff each hind leg with the two branches thus formed. Roll a piece of cotton around end of forceps and stuff fore legs. Place a stout straight piece of wire in the tail, wrapping it slightly to give the tail the plump appearance of life.
(If the cotton cannot be reeled on to the wire evenly, leave it off entirely.) Make the wire long enough to extend half way up belly. Sew up slit in belly. Lay mammal on belly and pin out on a board by legs, with the fore legs close beside head, and hind legs parallel behind, soles downward. Be sure the label is tied securely on right hind leg.
For directions for preparing and mounting skeletons of birds, mammals, and other vertebrates, see the books of Davie and Hornaday already referred to.
_Fishes, batrachians, reptiles, and other animals._--The most convenient and usual way of preserving the other vertebrates (not birds or mammals) is to put the whole body into 85 per cent alcohol or 4 per cent formalin. Batrachians should be kept in alcohol not exceeding 60 per cent strength. Several incisions should always be made in the body, at least one of which should penetrate the abdominal cavity. Anatomical preparations are similarly preserved. By keeping the specimens in gla.s.s jars they may be examined without removal.
Fishes should not be kept in formalin more than a few months, as they absorb water, swell, and grow fragile.
Of the invertebrates all, except the insects, are preserved in alcohol or formalin. The sh.e.l.ls of molluscs can be preserved dry, of course, in drawers or boxes divided into small compartments.
 The following directions for making skins of mammals were written for this book by Mr. W. K. Fisher of Stanford University, an experienced collector.
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