The deep branch of the obturator runs gene rally behind the adductor brevis, and divides into t%s o branches, one ramifying through the centre of that muscle : the other, for the supply of the adductor magnus. From the latter is given off a small articular nerve for the knee joint, which is directed downwards and out wards, towards the attachment of the adductor magnus to the linea aspera, perforates this attachment below the middle of the thigh, and is directed with the poplitwal artery into the ham,winding around the artery, and giving off an internal delicate branch, which enters the knee joint through the ligament of Winslow.
The Anterior Branches of the Sacral Are, yes are six in number, and escape from the anterior sacral foramina, decreasing in size from above downwards, and presenting, consequently, cha racters reverse to what obtain in the corre sponding branches of the lumbar nerves. They communicate with the sacral ganglia of the symphathetic, the filaments of communication being usually two between each nerve and the sympathetic.
The first nerve, smaller than the lumbo sacral nerve, extends more obliquely down wards and outwards, and having passed from the first sacral foramen, unites with it at an acute angle, and communicates with the second nerve.
The second none, somewhat smaller than the first, passes more obliquely downwards and outwards from the second anterior sacral foramen, and, having communicated with the third, enters the sacral plexus, sometimes bifurcating previously.
The third nerve, about one-third the size of the second, comes from the third sacral fora. men, and passes more horizontally outwards to the sacral plexus, having communicated with the second by a delicate filament sent in front of a portion of the pyriformis intervening between it and the second nerve.
The fourth nerve, considerably smaller than the third, passes from the fourth sacral fora men, communicates above and below with the third and fifth nerve, and terminates in three sets of filaments. One, usually in the form of a single trunk, is directed a little downwards and outwards, between the levator ani and the coccygmus muscle, gives branches to them. and finally becomes cutaneous. This filament in its course generally furnishes a small twig which perforates the great sacro-sciatic liga mgnt, and terminates in the skin over the border of the coccyx. A second, as a single
small trunk, passes to enter the sacral plexus. The third series anastomose freely with the k; pogastric pkxus, and then form of them selves a loose kind of interlacement, from which branches are given off to the rectum sides of the bladder, prostate, and vesiculm seminales, and the vagina in the female. The levator ani generally receives one or two fila ments, a distinct twig entering the middle, the other supplying the anterior part, after rami fying on the prostate.
The fifth passes from the fifth anterior sacral foramen, communicates above and below with the fourth and sixth, and sends a filament which perforates the coccyg.teus muscle, sup plies it, and terminates on the skin to the side of it.
The sixth (anterior branch of the coccygwal nerve) is extremely delicate, passing between the lower cornu of the sacrum, and the upper border of the coccyx, communicates within the bone with the descending branch of the fifth, and terminates by passing along the border of the coccyx in the substance of the sacro-sciatic ligament to become cutaneous. Some filaments are given off' from it which supply the coccygmus ; others perforate the ligament, and are lost in the substance of the glutmus maximus.
The Sacral Plexus (sciatic) is formed by the lumbo-sacral nerve and the four upper ante rior branches of the sacral nerves, principally, however, by the convergence of the three upper : the fourth sacral nerve sending merely a small filament of communication. The branches that contribute to its formation enter it at once, at a more or lez.s acute angle, with out any complex subdivision, as usuaily occurs in other plexuses. It has a well marked tri angular figure, the apex being indicated by the line of convergence of the different trunks : the base by the trunks as they issue from the sacral foramina. It rests upon the pyriformis muscle, the internal iliac vessels separating it from the pelvic viscera, being however in im mediate relation with a layer of pelvic fascia. Before terminating in the great sciatic nerve, the plexus gives off a series of anterior and posterior branches. Of the former are ob served, a nerve for the obturator internus, and the internal pudic : of the latter, the su perior glutwal, inferior glutal, nerves for the pyriformis, gemelli, and quadratus femoris.