Great care is necessary to keep the tiny carpal, tarsal, and phalangeal bones from getting lost. When the bones are white as chalk, or nearly so, tie the parts of each skeleton in a stout paper bag by itself, label it, and put it away until you are ready to mount it.
The sternum is to be soaked in clear water, with a little washing soda to cut the grease, until it is soft, and then sc.r.a.ped the same as the bones of a ligamentary skeleton, which process will be described in the next chapter.
CHAPTER x.x.xVIII.
CLEANING AND MOUNTING SMALL SKELETONS.
The skeletons of small vertebrates should never be macerated previous to mounting, for the reason that their complete rearticulation would be a practical impossibility. The bones must be left united at the joints by their natural ligaments, which when dry become quite hard, and with the aid of either one or two small bra.s.s standards will hold the entire skeleton erect and in proper shape. Skeletons mounted thus, with the parts attached to each other by their own dried ligaments instead of wires, are called ligamentous, or ligamentary, skeletons. All mammals smaller than a large fox, all birds smaller than a small ostrich, all turtles, lizards, iguanas, serpents, crocodilians, and all fishes are mounted in this way. Fortunately it is possible to clean to perfect whiteness the skeletons of almost all these subjects without putting them through the maceration process, which resolves everything into its component parts.
DRYING BEFORE MOUNTING.--In order to have a skeleton so that it will sc.r.a.pe to the best advantage and become as white as possible, every ligamentary skeleton must be dried before it is finally cleaned and mounted. In a perfectly fresh skeleton the epiphyses and ligaments are so soft the operator would find it hard to keep from destroying them with his keen-edged steel sc.r.a.pers, and the smaller bones and cartilaginous members would also be in great danger of mutilation in the same way. When a skeleton dries, all these soft portions harden, and when afterward the skeleton is soaked in clear water for two or three days, or longer as may be necessary, the flesh quickly softens so that you can sc.r.a.pe it all away without encroaching on the framework, and the ligaments at the joints are just soft enough that a portion of it may be sc.r.a.ped or trimmed away, and yet leave sufficient to hold each joint together.
RELAXING A DRY SKELETON.--As intimated above, this is accomplished simply by soaking the specimen in clear water until its joints are pliable, and the flesh upon the bones is soft enough to sc.r.a.pe off. In order that the specimen should not become offensive and disagreeable to work upon, it must not soak long enough for decomposition to set in, for that is the first stage of maceration. Therefore, sc.r.a.ping should begin just as soon as the flesh is soft enough to be readily removed.
[Ill.u.s.tration: FIG. 68.--Steel Bone-sc.r.a.pers.]
Sc.r.a.pING A LIGAMENTARY SKELETON.--The removal of the flesh and other animal matter from a small skeleton is accomplished by sc.r.a.ping the bones with various chisel-edged sc.r.a.pers specially designed for this work, and by clipping and tr.i.m.m.i.n.g on the joints with either curve-pointed or straight scissors. The principles to be learned in skeleton-sc.r.a.ping are comparatively few and simple. In the first place, a sufficient quant.i.ty of the connecting ligament at each joint must be left to hold the two bones together in proper shape when the specimen dries. This must not be left in a thick, unsightly ma.s.s, but requires to be sc.r.a.ped and trimmed down so that it is reduced to as small a quant.i.ty as will serve the purpose. In sc.r.a.ping the flesh off the main stem of a bone, such as the humerus, for example, always begin at the end and sc.r.a.pe toward the middle. The skeletons of turtles, lizards, and the like are an exception to this rule by reason of their structure, and should be sc.r.a.ped from the middle toward each end. If you sc.r.a.pe from the middle of a mammalian or avian bone toward either end, before you are aware of it, you have loosened the attachment of the ligament, and have nothing left to hold the joint together. By beginning on the ligament itself, and working away from it, you can sc.r.a.pe it down so thin at the point of attachment that its ident.i.ty is quite lost, and the point where it ends is hardly visible. This principle applies to the sc.r.a.ping of all ligamentary skeletons, except a few reptiles.
In cleaning bird skeletons beware of injuring the little tack like points which project downward from each of the cervical vertebrae. Have a care also for the soft bones of the coccyx, and the uncinate process which projects backward from the posterior edge of each rib. In fishes the greatest difficulty lies in leaving the ribs attached to the remainder of the skeleton, for if the operator is at all as the writer used to be in the days of his youth, he will be p.r.o.ne to sc.r.a.pe some of the ribs loose, and be obliged to glue them in place in the dry skeleton, with glue and cotton batting that has been clipped up finely with a sharp pair of scissors.
While a small skeleton is undergoing the sc.r.a.ping process it must not be allowed to get dry until it is finally set up in position. When the skeleton is not being worked upon, it must be kept soaking in clean water; but remember that this cannot go on very long, or maceration will set in, the ligaments will give way, and the bones will all come apart. A little borax in the water serves to arrest decomposition, and will allow a skeleton to remain soaking for several days longer than could otherwise be allowed. After a skeleton has been well sc.r.a.ped, in order to get it as white as possible and free from grease, it must be treated with
JAVELLE WATER.
1/2 pound chloride of lime.
1 pound common washing soda.
1 gallon of boiling water.
Keep this on hand in a gla.s.s-stoppered jar, in the dark. In using it, draw off a small quant.i.ty in a broad, shallow, earthen dish. Lay every small skeleton in it, and with a soft tooth-brush of the right size, brush all the bones thoroughly for about five minutes. At the end of that process wash the skeleton thoroughly with clear water, and perhaps it is then ready to mount.
Often the bones of a small skeleton contain an inordinate amount of grease.
The easiest and simplest way to remove it is to soak the greasy bones for several days or weeks, as may be necessary, in a jar of pure naphtha.
MOUNTING A SMALL SKELETON.--The skeleton of every bird, mammal, and reptile requires to have the spinal cord replaced by a stout zinc wire, to give both strength and rigidity to the structure. Zinc wire is necessary because iron wire will rust, and bra.s.s wire is too expensive to use when something cheaper and better is obtainable. If you cannot procure zinc wire, use good galvanized iron wire. For very large specimens you may use iron wire, but it must be covered with two coats of asphaltum, applied with a brush, like black paint. After inserting the wire the full length of the cavity of the spinal cord, leave enough of the end protruding beyond the first vertebra of the neck to afford a means for the attachment of the skull. The extra length to be allowed should always be nearly equal to the lateral depth of the brain cavity.
ATt.i.tUDE.--It is often somewhat difficult to decide upon the att.i.tude the skeleton is to have when finished. The possibilities in this line are extensive, and the result depends entirely upon the character of the subject, and the knowledge and good taste of the operator. In the first place, the position of the skeleton must be a correct representation of some characteristic att.i.tude of the species. For example, a sloth skeleton should hang underneath a branch; a monkey should be climbing, or walking on a stout bough; a hyena should sneak and crouch; a pa.s.serine bird should always perch, while the penguins and the auks must stand erect on flat pedestals. If the young osteologist can do so, it will pay him well to travel several hundred miles, if need be, to see the beautiful, and even elegant, collection of skeletons and other preparations in Mr. F.A. Lucas"s Department of Comparative Anatomy in the National Museum, all of the specimens in which have been prepared, mounted and displayed by Mr. Lucas and his a.s.sistant, Mr. Joseph W. Schollick. I know of no other osteological collection which in the beauty and scientific accuracy of mounting, and exhibition arrangement of its specimens, can be considered equal to this.
The museum-builder may well consider it a model of its kind. Every skeleton, from that of a tiny humming-bird to a whale forty-eight feet long, is as nearly perfect as human skill can make it, and the variety of the characteristic att.i.tudes represented in the smaller species makes this collection a particularly attractive one.
[Ill.u.s.tration: PLATE XX. LIGAMENTARY SKELETON (DOMESTIC CAT).--MOUNTED AND DRYING.]
PROCESS WITH MAMMALS.--We will a.s.sume that the skeleton has been carefully sc.r.a.ped, and is now ready for mounting. The successive steps in this work from start to finish are about as follows:
1. In case the skeleton has been dried after sc.r.a.ping, as is often done, it must be soaked in clear water until the ligaments are relaxed.
2. Cut a zinc or galvanized iron wire of the right length and size to replace the spinal marrow, and long enough that the upper end of it will project beyond the axis into the brain cavity of the skull. Sharpen one end of this wire so that you can force it well down into the sacrum, and insert it in its place in the spinal column.
3. Bend the vertebral column to its permanent shape. In doing this, draw the sternum well forward so that the ribs will spread out, and show a chest cavity of the right size for inflated lungs. If you are not careful in this regard, the chest cavity will be too narrow.
4. Hang the body in a frame made of light strips of wood, as shown in the accompanying plate. Let the body hang at just the right height from the pedestal to receive the legs (Plate XX.).
5. s.p.a.ce the ribs carefully by starting a thread from the neck, and taking a turn around each rib from the first to the last, finally making fast the remaining end of the thread to one of the lumbar vertebrae.
6. Put on each hind leg by drilling a small hole straight through the head of the femur and the socket of the pelvis (innominate bone), through which a small bra.s.s wire is to be pa.s.sed and clinched down closely at each end, to hold the head of the femur firmly in place.
7. Place each leg in the att.i.tude chosen for it, plant the foot according to its osteological character, and pin each toe in its proper place, as shown in the accompanying plate. The leg must be held in place by attaching threads to it, and making them fast to the various parts of the gallows.
8. In putting on the foreleg, the position of the scapula must be defined with accuracy, in order to avoid placing it too low or too high, and thus making an incorrect representation of the height of the animal. Bear in mind that the scapula never lies p.r.o.ne upon the ribs, but is separated from them by a cushion of muscle. It is therefore necessary to leave a certain s.p.a.ce between ribs and scapula.
9. Next cut two stiff bra.s.s wires of the proper length for the two standards that must support the skeleton (see _A A_ and _B B_ in Plate XX.). To make the U-shaped fork at the upper end of each standard, to clasp the vertebral column, heat one end of the rod red-hot, and plunge it into cold water, which softens the metal. Now put it in a vise, and with a hack-saw split the rod down the middle as far from the end as necessary.
Finish neatly by rounding off the ends with a fine file, and bending them in shape with the pliers. The lower end must have a thread cut on it an inch or so in length, a neat bra.s.s "rosette" screwed upon it (_R_) to do duty on the top of the pedestal, and a small bra.s.s nut made to screw on underneath the pedestal, to hold the standard firmly upright. These standards need not be put in place under the skeleton until it is mounted finally on its handsomely polished, permanent exhibition pedestal.
10. Mr. Lucas has two methods for attaching a small skull to the skeleton.
One is to cut a piece of cork to fit snugly in the occipital hole of the skull (foramen magnum), then pierce a hole through its centre, and fit it tightly on the projecting end of the vertebral wire, close up to the first cervical vertebra (the axis). The cork thus becomes stationary, and the skull may be put in place and removed at will.
The other method is to place the skull exactly in position on the skeleton, fitting it closely to the axis. Then drill a small hole through each side of the axis in such a manner that in its pa.s.sage from top to bottom the drill will also pa.s.s through the occipital condyle of the skull. By fitting a wire through each of these holes the skull will be held fast in position _so long as the skeleton remains in its place_, right side up.
If the skeleton is to be packed for shipment, the skull (unless it be very small and light) must be taken off, wrapped, and packed separately for safety in transit.
[Ill.u.s.tration: FIG. 69.--Skeleton of a Bat, as exhibited by Mr. Lucas].
11. If any bones have been broken, they must now be repaired, either by gluing them together, or by joining with a short wire fitted into the axis of each piece, and the missing particles of bone may be restored by a filling of best sinew glue mixed with plaster Paris into a paste, and applied hot, so that it will adhere. As it cools it can be shaped properly, and when thoroughly dry and hard, its surface must be dressed down with a fine file and sand-paper until the form of the bone is once more perfect.
This is work which very often calls for considerable skill in the operator, but the process itself is a very simple one.
If ligaments are missing and a small bone is completely detached, it should be put on as follows: Procure some fine cotton batting, cut it up very finely with the scissors, then apply some hot glue to the joint, lay a bit of clipped cotton upon it, and work it into the glue so that when dry it will form a false ligament and hold the bone firmly in its place without attracting any attention to the fact that the ligament has been made for the occasion.
12. Finally, transfer each skeleton to its permanent pedestal, which we will a.s.sume has been prepared while the specimen has been drying. Mr. Lucas puts all his small skeletons on handsome ebonized pedestals, which are the thing _par excellence_. The limbs for his climbing animals, and the thin, black boards for his bat skeletons are also ebonized. The ill.u.s.tration on page 291 (Fig. 69) shows one of his bat skeletons complete, as it stands in its case, bearing a label of black letters on an olive-gray card, with no ornamentation. In the final mounting the standards are put in place, and the upper end of each fitted fast to the backbone. Each toe is fixed firmly in its place, and held down by the bent-over end of a headless pin, or by having a pin put through it, and cut off close down to the bone.
[Ill.u.s.tration: FIG. 70.--Skeleton of a Bird Mounted and Drying.]
CAUTIONS AND EXCEPTIONS.--It is only the tiny skeletons, such as mice, shrews, small squirrels, and the like, that can safely be mounted without standards. To be sure, a large cat skeleton _can_ be mounted on its own legs, without any standards, and so can a man drink a pint of bad whiskey; but in each case the falling from grace will be in about the same degree, if not the same in kind also. In long-continued moist weather, ligaments are apt to soften and let large unsupported skeletons come down, without neatness, but plenty of despatch.
BIRDS.--The foregoing principles, which have been described in detail for small mammals, apply so fully and with such complete general similarity to birds, that it is only necessary to add the two accompanying ill.u.s.trations.
[Ill.u.s.tration: FIG. 71.--Wiring a Skeleton Wing.]
REPTILES.--_Serpents._--The skeletons of serpents should always be sc.r.a.ped and mounted as ligamentary specimens, and _not macerated_. The skeleton should be supported on from three to five low bra.s.s standards clasping the vertebral column at proper intervals, the body curved naturally, and the ribs spread out and s.p.a.ced evenly as in life, according to the curves of the body. The skeleton looks best when placed low down on the pedestal. The ribs must be s.p.a.ced with threads where the ligaments are soft, but when dry require no wires. The skeleton may be mounted in any life-like att.i.tude, either coiled or in motion.
_Lizards._--Small species are to be treated the same as small mammals.
_Crocodiles and Alligators._--It is best that all saurian skeletons, even the largest, should be sc.r.a.ped and mounted without maceration, on account of the elaborate cartilaginous sternum and false ribs. The head requires a special standard, and the tail requires a pair, while the tip of the latter is to be pinned down with a wire. Of course the feet must rest down on the pedestal as in life. One thing which would greatly enhance the scientific value of every crocodile and alligator skeleton would be the preparation and display, in its proper place, of one side of the skin of the back with its wonderful shield of bony plates nicely articulated together. This remarkable covering of the vital organs seems to have been specially designed to ward off glancing bullets, and it has saved the lives of thousands of crocodilians. (Of course this shield is not proof against a bullet fired squarely against it.) So far, all collectors and osteologists have ignored this remarkable feature of the saurians, but it should have the attention it deserves.
[Ill.u.s.tration: FIG. 72.--Skeleton of Turtle, as Exhibited.]
_Turtles and Tortoises._--The skeleton of a tortoise, if mounted on its feet in a life-like att.i.tude, has the best part of its anatomy concealed by its sh.e.l.l. This difficulty Mr. Lucas meets occasionally by sawing out and laying back one-half the carapace, to expose the interior. The commonest method, however, is that shown in the accompanying ill.u.s.tration (Fig. 72), which is self-explanatory. The plastron is hinged at one side, furnished with a latch, and opens like a door. The skeleton is mounted on a single standard, which is split at the upper end like a Y, the arms bent to fit the curvature of the sh.e.l.l, and riveted to the carapace. Each leg is held in place by a small wire attached to the sh.e.l.l at its edge.
FISHES.--There is nothing in the mounting of fish skeletons that has not been fully described in the foregoing pages. Of course fish skeletons are never macerated, but must be sc.r.a.ped and mounted with their natural ligaments in place. Each skeleton requires two bra.s.s standards, one clasping the vertebral column close to the tail, the other near the head. A very long fish, or one with a large skull, requires three standards, one for the skull and one for the middle of the body. Where only two are used for a large fish, the head requires to be supported by a wire running from the centre of the backbone.