mended by Hasevroek, which allows some joint motion. If this fails, exploratory arthrotomy should be performed. In some cases the cause will be found to be quite simple, such as a loose cartilage, or a stretched or torn ligament. The cartilage should be removed and the ligament fixed by suture. Other cases will be more complicated. The condition, however, must be rare, because there is little in the literature on the subject, and even in a large surgical experience one observes these cases very infrequently.— ED.]

Under certain circumstances a dislocation may be irreducible. It may happen that, in spite of persistent efforts at reduction under anesthesia, it is found impossible to put the bones in place. Failure may be due to the small size of the tear in the capsule, but, as a rule, it is due to the interposition of soft parts. If the edge of the articular surface was broken by the injury, it is evident that reduction may be impossible. In all such cases bloody reduction of the dislocation ought to be resorted to as early as possible. The joint must be opened as much as may be necessary to effect reduction.

[In experienced hands, when reduction of a dislocation fails after the proper trial of the usual methods one should never hesitate to operate at once. Prolonged and forcible attempts at reduction are dangerous. With proper technic the operation is a very simple matter, and seldom fails to reduce a recent dislocation. In the majority of instances one will find a sufficient cause which prevented the usual easy reduction of the dislocation; for example, a small fragment of bone, or an interposed tendon or muscle. -ED.]

If a dislocation is not reduced, there results the condition known as an "old dislocation," complicated frequently by the formation of a new joint (a nearthrosis). Therapeutic measures in such cases will be determined by the conditions found on careful examination. If the function of the new joint is satisfactory, as happens in very rare

cases, no interference is indicated, and the surgeon should confine his efforts to enhancing the mobility of the new joint by means of passive exercises, etc.; but if the opposite is the case, there is nothing left but resection or arthrotomy, followed by the replacement of the dislocated articular head in the original cavity. The latter should be the usual procedure, if for no other reason, because these cases of unreduced luxations are presenting themselves for treatment earlier than they used to, and because the results obtained by replacement are, as a rule, much better than anything that can be hoped from resection. It is always more desirable, however, that reduction be effected as early as possible.

[There is really no necessity for an old dislocation. In the recent state reduction is always possible. Nevertheless many cases come to the surgeon. The same rules should be followed in the reduction as those advised for recent dislocations: first, an attempt at reduction without operation, always under anesthesia; if this fails, an immediate operation, so that the patient is subjected to only one narcosis. In some cases of old dislocations resection gives much better results than reduction; this is especially true at the shoulder and elbow. The functional result of a proper excision of these joints is always excellent. On the other hand, in cases in which perfect reduction is possible, the joint changes from the old injury are so advanced that marked restriction of motion is always present, and the function of the arm is never as good as after a resection. Experience and the study of the soft parts around the joint will usually indicate the better procedure.-Ed.]

II. FRACTURES OF THE SKULL

In the study of fractures of the skull it is of interest to know that the doctrine of a certain elasticity of the skull promulgated by Bruns has been confirmed by recent inves

tigations carried out with the best instruments and under the observance of all necessary precautions. The skull, in fact, possesses a certain elasticity; and a force acting on it from without must overcome the limit of its elasticity before producing a fracture. This is equally true of fractures of the base of the skull.

(A) FRACTURES OF THE SKULLCAP

In fractures of the vault of the cranium it is noticeable that the inner table suffers more extensively and exhibits

Fig. 23.-A B represents the segment of a skull, a b showing the points of impact of an external force. The first effect of the force is to produce a certain flattening of the skull, as at A' B'; at the same time the point of impact at a b is compressed and the corresponding portions of the internal table are stretched, the particles of bone being pulled apart to the point of bursting. This is readily understood by comparing the quadrilateral a bed in the two figures. (After Teevan.)

greater dislocation of its fragments than the outer table. This phenomenon was formerly explained by assuming a greater brittleness for the inner table, which was accordingly named tabula vitrea. In recent times it has been found that the phenomenon depends on certain simple mechanical laws, and that in any injury of the vault that table which is furthest removed from the injuring force suffers the most extensive fracture. A glance at the illustration on Plate 9 suffices to show the important fact that an injury of the vault of the cranium from within-that is, from the cavity of the skull-produces the same appear

PLATE 9.

Fractures of the Vault.-Fig. 1.-Gunshot wound from without and from within. Fragment of the skullcap of a cadaver showing the marks of two bullets fired with a small charge of powder, one bullet striking from without, the other from within. The direction of the bullets is indicated by arrows. The section shows that the point of entrance represents a round hole, while the point of exit is marked by a larger and more irregular loss of substance. collection.)

(Author's

Fig. 2.-Effect of a projectile with low velocity discharged from without (artificial). The force was not sufficient to perforate the skull; the point of impact on the skull is marked only by a slight depression, while the internal table shows extensive shattering of the bone. (Author's collection.)

Figs. 3 a, b, c.—Qld fracture of the skullcap with depression of the fragments. Firm union of the bone had taken place with some thickening at the seat of fracture. Figure 3 a shows the preparation from within; figure 3 b, from without; figure 3 c, in transverse section. In this preparation also the splintering of the internal table is more extensive than that of the external. (From the collection of the Path. Anat. Institute at Greifswald.)

ance of more extensive shattering on the outer table as is usually seen on the inner table under ordinary circumstances, when the injuring force is applied to the skullcap from without. According to Teevan, it appears that the effect of a force acting from without, such as a spent ball, a small stone, or a stick, is to induce a certain bending of the skullcap at the point of impact. This bending process, as long as it is confined within the limits of elasticity, produces only a slight flattening of the normal curve of the bone. The particles of bone in the external table are compressed, while those in the internal table are distended; i. e., forced apart. Just as when a stick is broken over the knee the fracture begins on the convex side, that is, the side on which distention and separation of the particles take place, so in the same way the fracture begins and becomes most extensive on the distended side of the skull