SHOTGUN. 121 SHOVELEK. action; it was known as the douhlc-r/rip hrccch mechanism. Next came the sliding barrel breech mechanism as first employed in the Bastin Lepagus breccli loader. Instead of beinj; hinged, the bar- rels were so constructed as to slide backward and forward on the fore part of the stock. The idea was not very successful and soon fell into disiise. The conil)inalion of the Bastin and Lc- faucheux principles was seen in the Duugall lock- fiixt brrrch mechanism, in which the barrels turned upon a hinge pin and were moved to and fro on the stock sufficiently far to clear and make contact with the projecting disks attached to the standing breech. To load, the lever was dcjiressed, the eccentric hinge-pin turned, and at the same time the ban-els moved forward until the lireech ends were clear of the disks, after which the barrels were dropped as in the original Lcfaucheux. Of all the difl'erent varieties of the inrn-ovcr breech mechanism which have been tried (at the best with indifferent success), that invented by the Englishman JefTries in • 1862 is about the best known. The great effort of inventors and gunmakers was to dispense with the drop-down or Lcfaucheux method for sport- ing guns, and the breech mechanism of .Teffries is probably the most satisfactory stibstitute, fail- ure though it was. The barrels turned on a vertical ]iivot by means of a lever which was pivoted vertically imder the breech-action body. In America the Fox shotgun followed the same idea, but abandoned the lever. The needle gun adopted by the Prussian Army in 1842 was an improved type of the early central-fire gun, the breech mechanism of which formed a combina- tion of the sliding and drop-down principles. The inventor of the central fire-gun of this type was one Dreyse of Sommerda. A similar weapon was Needham's of 1850, in which the cap of the cart- ridge was at the base. The Lancaster central- fire system made its appearance about 1852. The barrels followed the principles of the Dreyse gun, but the cartridge case, instead of being con- sumed, was withdrawn by an extractor after firing. An improved central-fire system, and one which in its many essentials has been carried to the present day, is said to be the invention of W. Pottet. a Frenchman. Improvements in locks and minor mechanisms came next, the reboimd- ing lock, in which a main spring reacts upon the tumbler, automatically raising it to half-cock, having been introduced about 1806. The Wesley Richards breech-loader dates from 1S62 and was one of the first to introduce a toji lu'cech-bolt mechanism. Hammerless guns date from the era of a consumable cartridge case, although no par- ticular claim was put forth in their favor. The development of the principle was interfered with by the success of the pin-fire gun, in whieh ex- ternal hammers were a necessity. There were many varieties of hammerless guns, notablv those of Daw (18G2). Greener (1800), and Murcott ( 1871 ) . The Murcott weapon was the first of the hammerless variety to achieve success. The Anson and Deelet/ gun. (1875) was a very popu- lar mechanism. The leverage of the barrel-cock- ing mechanism was obtained bv the falling of the barrel. When the hammerless weapon was first introduced in its modern form it was very strongly opposed bv both sportsmen and gim manufacturers. Other important improvements were in connection with the ejecting mechanism : notably Needham's hammerless ejector gun, in which the extractor is in two halves, and the I'crkes mechanism, by which the cartridge cases were ejected by a separate mechanism situated in the fore part of the gun. Kight years later the Dcelcg ejector mechanism made its appearance, in which locks and barrels are fittecl with an ejecting lock mechanism in the fore end. For a long lime England held the su])remacy in the manufacture of shotguns and sporting firearms, but it is generally conceded that .Vmerican wea- pons have now the preeminence. The leadiuij American manufacturers of shotguns are the L'olt's Arms Comjiany. Remington Arms Company, Smith and Wesson Company, and the Winchester Arms Company. SHOULDER- JOINT (AS. sculdor, OIIG. scullirra. (ier. Schnllcr: of unknown etymology). A ball-and-socket joint formed at the junction of the humerus and scapula. The large globular head of the humerus is received into the shallow glenoid cavity of the sca]iula, by which arrange- ment extreme freedom of motion is obtained, while the apparent insecurity of the joint is pre- vented by the strong ligaments and tendons which surround it, and also by the arched vault above formed by the under surface of the acromion and coracoid processes. (See Scapula.) As in movable joints generally, the articular surfaces are covered with cartilage, and there is a sj'novial membrane which lines the interior of the joint. The most important connecting medium between the two bones is the capsular ligament, which is a fibrinous expansion embracing the margin of the glenoid cavity above, while it is prolonged upon the tuberosities of the humerus below. The morbid affections of the shoulder-joint may be divided into (1) those arising from disease and (2) those dependent on an accident. The slioulder- joint is not as liable to disease as the other articulations : it may, however, become the seat of a synovial inflammation, active, subacute, or chronic, and less often of tubercular .syphilitic or rheumatic disease. There may be fracture (1) of the acromion process, or (2) of the cora- coid process, or (3) of the neck of the scapula, or ( 4 ) of the superior extremity of the humerus ; or two or more of these accidents may be asso- ciated. Again, the head of the humerus may be dislocated from the glenoid cavity in a direc- tion above, below, in front, or behind this cavity. The anterior variety is most frequent. The fol- lowing are the most prominent symptoms: The arm is lengthened; a hollow may be felt under the acromion, where the head of the bone ought to be; the shoulder seems flattened; the elbow sticks out from the side, and cannot be made to touch the ribs; and the head of the bone can be felt if the limb be raised, although such an at- tempt causes great pain and weakness from the pressure exerted on the axillary plexus of nerves. For a description of the symptoms and mode of treatment of fractures and dislocations, consult Park, Surgery by American Authors (New York, 1901). SHOVELEB (so called from the shape of its bill). A cosmopolitan fresh-water duck of the genus Spatula, remarkable for the expansion of the end of the mandibles, the lanicll.TP of which are long and very delicate. The legs are placed near the centre of the body, so that these birds walk much more easilv than many of the ducks. The common shoveler( Spa <»?o c?!/pea(o) is smaller
