CHAPTER x.x.xIX.

MOUNTING A LARGE DISARTICULATED SKELETON.

It will be well for anyone who intends to mount a large skeleton, if he has not already a fair knowledge of osteology, to take some book which contains a description of the skeleton, for example, of the domestic cow, and familiarize himself with the names of the various bones and the different anatomical terms used in describing them. In fact it is next to impossible to describe the process of mounting a skeleton without making use of quite an array of technical terms.

In order to make our description of this intricate process as clear as possible, we will choose as our typical subject the skeleton of an American bison, and go through with it in detail, aided by an abundant supply of ill.u.s.trations. We of course a.s.sume that the macerating, cleaning, and bleaching has been done.

In mounting a disarticulated skeleton, begin with the vertebral column as the key to the situation. It is, in point of fact, the keel upon which the whole structure is to be built. The vertebrae should be arranged, each in its place, and, then they should be numbered with pen and ink on the anterior articulating surface of the body of each one, beginning with the first vertebra in front of the sacrum. This vertebra (the last lumbar) should be marked No. 1, the next in front No. 2, and so on to the axis.

The next step consists in boring two holes through the sacrum from its under surface (Fig. 73, _a, a_) to its anterior articulating surface (_b, b_), and these holes should be continued on through the body of each of the succeeding vertebrae to the axis. They should come out underneath that vertebra (the axis), where the wires which pa.s.s through all these holes are afterward to be twisted together. The holes should be somewhat larger than the bra.s.s wires which are to pa.s.s through them.

It is necessary to mark the place for starting the drill into the posterior surface of each vertebra by fitting two articulating surfaces together, and pa.s.sing the drill through the holes already made. The points at which the drill should come out on the anterior surface of a vertebra should be marked with a lead pencil. The beginner will find some difficulty in making the drill come through at precisely the right spot. The greatest difficulty will be experienced in getting these holes through the cervical vertebrae.

When the axis is reached, bore the holes so that they will come out underneath, about half way between each extremity of the vertebra, and about three-fourths of an inch apart.

It is just as well to now bore the holes through which the wires which fasten the axis and atlas together are to pa.s.s, though these need not be actually united until the remainder of the spinal column has been, articulated. The wires uniting the atlas and axis are smaller than those pa.s.sing through the spinal column. The holes for these wires are made by boring two of them through each of the two surfaces by which the axis articulates with the atlas. These holes should come out underneath the axis. Then, placing the axis and atlas together, mark on the atlas the places through which the holes are to pa.s.s by running the drill through each of the holes already made.

The next thing to be done is to cut pieces of artificial cartilage, called "buffle," to fit the posterior articulating surface of the body of each vertebra, and each piece should be fastened to the vertebra to which it belongs by a small wire nail through its centre. The holes in each vertebra should be continued straight on through the false cartilage. Now cut a bra.s.s wire three times the length of the spinal column, double it, pull it straight, pa.s.s the two ends through the sacrum, and so on forward through all the vertebrae.

When the vertebrae have all been strung on the two wires and tightened up, it will be seen that the spinal column a.s.sumes a curve approximating very nearly to the natural one. Mark this curve with chalk on a table or a board.

Unstring the vertebrae from the wire. Then take a square rod of iron, a foot or so longer than the spinal column, and over which each of the vertebra will fit easily. Have the blacksmith flatten out one end into a sort of spear, so that it will fit snugly in the spinal ca.n.a.l of the sacrum (Fig.

73, _c_).

[Ill.u.s.tration: FIG. 73.--The Sacrum and Spinal Rod.]

Drill a hole through the under surface of the sacrum, and on through the iron rod: Into this a bra.s.s pin is to be fitted at _d_. Bend the iron rod to correspond exactly with the curve previously marked with chalk on the board. Paint the rod black, and when it has dried place it again in the sacrum, drive in the bra.s.s pin, leaving enough of the end exposed to be seized with a pair of pliers and pulled out if desired. Now string the vertebrae over the rod and wires. If all fit properly they can then be unstrung preparatory to attaching the ribs to them.

[Ill.u.s.tration: FIG. 74.--The Attachment of the Ribs to a Vertebra.]

Each rib should have a hole bored through its lower end at the middle, to come out on the inner surface (Fig. 74, _b, b_). Through these holes wires are to pa.s.s, as seen in the accompanying figure, and to these wires the sternum is presently to be attached.

Having arranged the ribs so that you know the place of each, take the first pair, and the first dorsal vertebra to which this pair attaches. Bore a hole with the drilling machine through the rib, beginning at the centre of the articular surface of the tubercle of the rib, directing the drill so that it will come out on the under side (Fig. 74, _c, c_); then drill a hole through the head of the rib (_d, d_). Now fit the rib to the vertebra, and with a small awl, a sharp-pointed wire, or drill, mark, through the holes already made, the points on the articular surface of the vertebra through which the holes should be drilled (_a, a_). Bore similar holes through the rib of the opposite side, then through the vertebra at the points marked, and the wire will pa.s.s through as in the figure.

[Ill.u.s.tration: PLATE XXI. SKELETON OF AN AMERICAN BISON.]

Continue this same process for the remaining ribs. It will be found, however, that the process of carrying a single wire through the heads of both ribs and the anterior portion of the body of the vertebra cannot be continued with all. In the last of the dorsal vertebrae the wires will have to be put through the head of the rib and the pedicles of the vertebrae into the neural ca.n.a.l.

Make a loop on the end of each wire, as at _a, a_, Fig. 74, and put the ribs on each vertebra as they belong, having only one end of the wire--the one on which is made a double loop--pulled up snugly. The other end of the wire should be left a few inches in length, but bent slightly close to the rib, to hold the latter in place.

The innominate bones should be attached to the sacrum either by two bra.s.s bolts, one pa.s.sing through each side at about the middle of the articular surfaces between the sacrum and each ilium, or by pa.s.sing a heavy double wire through each of these places. Before tightening permanently, apply "plaster-glue" (the mixture of glue and plaster Paris already described) to the articular surfaces between the sacrum and ilia, thus when dry making the pelvis firm.

Now that the ribs are attached to the vertebrae, and the innominate bones to the sacrum, proceed to string the vertebrae again on the wires and rod. The atlas can now be attached to the axis by pa.s.sing wires through the holes previously made, after which the wires are to be twisted firmly together.

When all the vertebrae with their ribs attached have been put in place, hang the backbone to a framework similar to that used for suspending the alligator (Plate XIV.), or, what is much better, to the ceiling, by two small ropes attached at the neck and pelvis.

With the pliers now twist tightly together the wires under the axis, then take a screw-driver and work between each pair of vertebrae from underneath, beginning with the last lumbar, and prying back toward the sacrum. By the time you have reached the axis a considerable s.p.a.ce will have been gained. Shorten the wires by twisting them, and continue this process until the vertebrae all fit snugly together, and are tight one against the other.

[Ill.u.s.tration: FIG. 76.--Middle Joint of the Hind Leg.]

The next step is to put on the sternum, which has been soaked in water containing a little washing soda, and thus made flexible. Of course it has been previously cleaned by the sc.r.a.ping process. A hole should be bored through the end of each sternal rib, coming out on the inner surface. The sternum is suspended temporarily by strings attached to the vertebral column, and the single wires that have previously been placed through the end of each rib are now run, one by one, through the end of the sternal rib it is to support.

Now s.p.a.ce the ribs temporarily with a string that will hold each one of them exactly in its place. Having done this, two bra.s.s wires can now be used to hold the ribs permanently in place, running them on each side from the inferior process of the last cervical vertebrae to the transverse process of some one of the lumbar vertebra, or to the pelvis. What is much better for a large skeleton, because it is both firmer and more elegant, is a long, narrow strip of polished bra.s.s on the inside, bent carefully to fit the curve of the ribs, and fastened by a bra.s.s pin through each rib, the posterior end of the bra.s.s strip being attached to a transverse process of one of the lumbar vertebrae (see Plate XXI.). After this has been done, each rib can then be permanently fastened at top and bottom by making the loop and cutting off the long end of each wire.

The next step is to put on the tail. A hole should have been bored into the middle of the articular surface of the posterior end of the sacrum, and on each side a little hole coming out below (see Fig. 73). The large middle wire (_e, e_) should be of stiff bra.s.s, and extend through the entire length of the tail, the tapering end being filed small so that the small vertebrae can fit over it. The small side wires of soft bra.s.s (_f, f_) should only extend through a few of the larger tail vertebrae, and are for making things firm.

[Ill.u.s.tration: FIG. 76.--Middle Joint of Hind Leg: Rear View.]

[Ill.u.s.tration: FIG. 77.--Bones of the Foot: Side View.]

To articulate the bones of the hind leg, first arrange them so as to know the precise place of each. Take first the tarsal and metatarsal bones. In articulating these it is necessary for one to use his judgment largely, and put wires through so as to make the joint firm. Bore holes through the astragalus and os calcis (Fig. 75, _a, a_) so as to put a double wire through these and hold them together firmly. Next send two strong double wires through these and through the other tarsal bones, and bring them out on the posterior surface of the metatarsal or canon bone (_c_ and _d_).

[Ill.u.s.tration: FIG. 78.--Bones of the Foot: Rear View.]

Next articulate the bones of the feet. This is very simply done by pa.s.sing a single heavy wire through the lower end of each half of the canon bone to each set of phalanges, making a loop at each end of the wire (see Figs. 77 and 78). In large skeletons it will frequently be found necessary to further strengthen the articulations of the phalanges by means of bra.s.s pins, as shown in the figure at _a_. The sesamoids are fastened on by two stiff bra.s.s pins through each at _b_.

The femur and tibia can be fastened together by a double bra.s.s wire pa.s.sing through each condyle of the femur, and through each side of the head of the tibia, or, what is better, a strip of bra.s.s set into the middle of the joint, and fastened firmly by two stout bra.s.s pins driven transversely through from side to side, as indicated in Fig. 79.

[Ill.u.s.tration: FIG. 79.--The Knee-Joint.]

The patella is fastened on by pa.s.sing a wire through it and twisting it, or erecting it on a small strip of bra.s.s set into the tubercle of the tibia.

The joint is further strengthened by putting a bra.s.s pin through the patella into the end of the femur.

The tibia is articulated to the lower portion of the leg, or, more properly, the pes, by putting stiff wire pins into it. The femur is articulated to the pelvis by a bra.s.s bolt. The front foot is articulated on the same principles as the hind foot.

[Ill.u.s.tration: FIG. 80.--Front View of Knee-Joint.]

In articulating the knee-joint, as it is called, send two heavy wires through, letting them come out on the posterior surface of the radius and metacarpal bone, and insert two wire pins diagonally through the joint, as shown in Fig. 81. The scapula is fastened to the humerus by bra.s.s pins. The humerus, radius, and ulna are also fastened by bra.s.s pins, three in number.

[Ill.u.s.tration: FIG. 81.--Elbow Joint: Front View.]

The scapula is attached to the body by two bra.s.s bolts attached to the ribs. Sections of spiral spring wire or pieces of bra.s.s tube are placed on the bolts between the scapula and the ribs, to hold the former off the latter the same distance as when the flesh surrounding the scapula was all present. As to the position of the legs, the operator must use his own judgment. It is of course to be understood that the att.i.tude of the legs has been decided upon before their articulation began, and that the work of wiring together has been carried out in accordance with this plan. It is hard to do more with a large skeleton than to place the legs in an easy walking att.i.tude, of which the buffalo skeleton already figured may fairly be taken as a model.

The rod extending through the spinal ca.n.a.l is cut off so that the head will hang on it properly. Two bra.s.s pins are pa.s.sed through the atlas, one into each occipital condyle. Two iron rods, with lacquered bra.s.s shoulders, are used to support the skeleton, as shown in the figure. These rods should be painted black.

The lower jaw is fastened to the skull by means of bra.s.s spiral spring wire, which permits it to be moved freely up and down by any one who is studying the animal's dent.i.tion.

The method of mounting any large disarticulated skeleton of a quadruped is essentially the same as that described for the buffalo, the principle variation occurring in the feet. In articulating the feet of a wolf, for example, the method of wiring the tarsal bones, carpal bones, metatarsals, metacarpals, and the phalanges, is very similar to that described for the buffalo, but the workman must here also depend largely on his own ingenuity. A single wire pa.s.ses through the phalanges of each digit, and two sesamoids are fastened on by a single wire.

Where the digits are more than two in number, a wire is pa.s.sed transversely through the lower ends of the metacarpals and metatarsals, and on this are placed short pieces of fine coiled bra.s.s spring, to hold the digits at proper distances from one another.

The tools used in mounting large skeletons are by no means so numerous or costly that any one need be deterred from trying his hand at practical osteology on the score of facilities or the lack of them. Of course the complete outfit of a professional osteologist includes an extensive array of tools, some of which are rather costly. The most important item is a good drilling machine, chuck and lathe, to work by foot-power. This can be procured of Goodnow & Wightman, of Boston, and in ordering it will be necessary to have a 1/4-inch hole drilled through the centre of the axle, to receive the long, steel drills of various sizes that are to drill the many holes required in the various bones.

The amateur who can not afford an expensive plant and a first-cla.s.s drilling machine, can get along very well with a Millers' Falls hand-drill and a good a.s.sortment of first-cla.s.s steel drills to fit it. I once saw an old German anatomist mount a cow skeleton for a Western college with hardly more tools than I could hold in one hand--but, of course, that skeleton was not mounted _a la Lucas_, by a considerable difference.