It in the area supplied by the right median nerve, and there was a slight weakness of the flexors of the fingers. On the following day, the tingling had become a slight steady pain. By the end of the fifth day, the patient was suffering agonies. was evident that some progressive lesion was present-either a scar tissue formation enclosing the nerve or a rapidly growing intraneural tumor. At the operation, a hæmatoma the size of a small chestnut was found within the nerve, and upon its enucleation the pain at once subsided. 2. If the symptoms are regressive, do not operate. Thus, it not infrequently occurs that when a patient is brought into the hospital there is a complete paralysis of the muscles supplied by the musculospiral. Three weeks later, when the wound is healed and the muscles are tested after removing the splint which has kept the hand constantly in the hyperextended positions, a faint flicker of movement may be discernible in the muscles previously completely paralyzed. In this case, the prognosis is excellent without operative interference, since the nerve has probably been slightly traumatized by pressure or blood extravasation and has not suffered a severance of its continuity. 3. In other cases, where there is no change whatever in the extent of the paralysis or of the sensory symptoms, wait until the wound has healed, and then determine on the basis of the anatomical course of the nerve and the direction of the bullet whether there is a strong probability that the nerve was directly injured by the passage of the projectile. If so, operate; if not, wait still longer. This rule requires the most accurate anatomical knowledge and a good eye. If observed with care, it will seldom lead the surgeon into error. The electrical tests are, in my experience, of little or no value in deciding whether operation is indicated. It frequently occurred that in cases, in which all the muscles showed a typical reaction of degeneration, and operation was advised by the electro-diagnostician, perfect recovery occurred without operative interference. Whereas in other instances, in which the electrical reactions were such as to lead an expert to advise conservative treatment, operation showed a complete division. of the nerve. The great advantage gained by performing operation at an early date is made evident by the pathological conditions which confront one after gunshot injuries to the nerves. Two types of injury have already been mentioned (1) a traumatism of the nerve, due to the passage of the bullet in its immediate neighborhood, without severance of any nerve fibres; (2) the presence of a small hæmatoma within the nerve. FIG. 82.-Injury due to downward path of projectile which grazed the angle of the jaw. a, The small flesh wound. b, The right facial paralysis, evidenced by inability to raise the angle of the mouth, due to concussion of the facial nerve. The paralysis disappeared one week subsequent to injury. A number of other pathological possibilities may be present: (1) There may be a concussion of the nerve, without any evidence of traumatism. Thus, in Fig. 82 is shown the photograph of a patient who gave all evidences of a facial paralysis, although there was no wound in the immediate neighborhood of the nerve. The paralysis subsided after five days-a sure indication that no real traumatism of the nerve could have occurred. (2) The nerve may be partly divided by the bullet. At the point of injury, scar tissue develops, producing a small hard nodule, which may lie either toward the periphery of the nerve or near its centre, depending upon the exact site of the laceration. (3) In other instances, the nerve is completely divided by the projectile. In some cases the nerve ends remain in contact and are rapidly united by scar tissue, which may be minimal in amount or may be sufficiently great to completely obstruct the downward growth of the axis cylinder processes. In still other cases (and this is, according to my experience, the rule) the nerve ends are forced apart by the projectile and lie separated from one another, so that the continuity of the nerve is completely interrupted. The nerve ends become rapidly embedded in scar tissue, and their ends show the fibrous enlargement typical of the divided nerve, which is unable to regenerate. It is clear that the longer the operation is postponed in such cases, the greater will be the development of scar tissue and the more extensive the degeneration of the nerve, both ascending and descending. (5) In addition to a hæmatoma within the nerve, there may also be small particles of lead, clothing, etc., within its substance which usually cause intense pain although seldom complete paralysis. The operative treatment of nerve injuries depends upon a knowledge of the physiological processes involved in nerve regeneration. Whatever differences there may be in the present attitude of physiologists and neurologists toward this question whether the regeneration is due entirely to the downward growth of the axis cylinder processes from the proximal stump into the distal, or whether the opposing school is correct in its contention that the sheath of Schwann of the distal stump contributes to the regeneration-one fact is admitted by all: that the conditions for regeneration are most favorable when there is an intimate union between the axis cylinder processes of the divided nerve ends. Upon this fact the operative treatment is based. In all instances, the operator must try to secure this intimate union between the axones whose continuity has been interrupted by the projectile. The exact method applicable to the case depends upon the nature of the pathological process which is found at the operation. 1. If the nerve is seen to be merely traumatized or pressed upon by a bone fragment or scar tissue, nothing should be Should done except remove the external cause of the pressure. this be due to scar tissue, some means must be taken to prevent its recurrence. This is best done by changing the position of the nerve from the area where scar tissue is likely to develop into one where it is surrounded by normal healthy muscles. As a rule this is readily accomplished by suturing the muscles FIG. 83. Method of nerve suture after excision of scar tissue invading a portion of the nerve. Fig. I.-BAB', The line of excision of the neuroma. The sutures (dotted lines) pass through the perineurium. When drawn taut, as shown in Fig. II, B is approximated to B', producing a little projection of the nerve. Prognosis in these cases is good because of the accurate approximation obtained by this method. which normally are superficial to the nerve in such a fashion as to bring them deep to the nerve-that is, interpose them between it and the scar tissue. If this is impossible—as, for instance, in the case of the external popliteal nerve, where it rounds the head of the fibula—the nerve should be ensheathed in fascia, its smooth inner surface turned inward, or in a tube of calf's artery hardened in alcohol (see footnote). 1 The method of preparing the artery is as follows: Arteries of varying size are mounted on glass tubes of appropriate diameter and hardened in 10 per cent. formalin for three days. They are then thoroughly washed in running water, boiled for half an hour and kept in 90 per cent. alcohol. At a secondary operation, two months subsequent to the implanting of such an artery, I found its intima still smooth and the nerve absolutely free from adhesions. 2. If a small nodule of scar tissue is felt within the nerve, indicating its partial division by the projectile, this area should be excised and the corresponding axis cylinder processes united by fine perineural stitches (see Fig. 83). In these cases the prognosis is particularly good, since it is easy to secure accurate apposition (see Fig. 84). 3. If scar tissue is generally present throughout the nerve, two courses are open, dependent upon its degree of development. If a small quantity is present, then by careful dissec FIG. 84. Photographs (two exposures on one plate) illustrating the effect of nerve suture by the method shown in Fig. 83 eight weeks subsequent to the operation. tion this can be removed from within the substance of the nerve without disturbing the continuity of the nerve bundles. This operation is known as internal neurolysis. If, however, an extensive scar tissue formation is present, completely interrupting the course of the axones, the area must be entirely excised and a suture of the nerve performed. 4. When a nerve has been completely divided, there is nothing to be done except nerve suture. In performing this delicate operation, no surgeon at the present day has a right to urge his method authoritatively, since the present status of nerve suture is an uncertain one. We do not know whether the perineural stitch advocated by most men is preferable to the |