SPINAL NERVES. 



765 



tinacus, which varies in its size according to 

 whether this muscle be supplied by the ac- 

 cessory obturator or not : and a third to the 

 adductor longus, which also enters its posterior 

 surface. 



The most important branch, however, is 

 the long cutaneous branch which emerges from 

 behind the lower border of the adductor lon- 

 gus muscle, passes in the fascia behind the 

 internal saphaena vein as far as the knee joint, 

 where it perforates the fascia, and becomes 

 cutaneous at the anterior border of the tendon 

 of the gracilis muscle. In this part of its 

 course, a little below the upper third of the 

 thigh, it communicates either with the internal 

 branch of the accessory saphtenus, or with a 

 branch occasionally given off from the saphae- 

 nus itself, and which accompanies the saphaena 

 vein to the knee joint. It gives off cutaneous 

 branches to the middle of the thigh, forming, 

 with the above nerve, a more or less intricate 

 plexus. Having perforated the fascia on a 

 level with the knee joint, above it, or a little 

 below it, it communicates with the trunk of 

 the internal saphaenus (being occasionally 

 only in apposition with it), and internal cuta- 

 neous nerve. It terminates by being directed 

 downwards and backwards to above the lower 

 part of the poplitaeal region, and continues to 

 give off cutaneous branches, till it is lost in 

 the integument at the inner and back part of 

 the leg to within two or three inches of the 

 ankle : having previously sent filaments of 

 communication to the continuation of the 

 saphaenus nerve. 



The deep branch of ihe obturator runs gene- 

 rally behind the adductor brevis, and divides 

 into two 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 poplitaeal 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 Ne> ves 

 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 nerve, 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 coccygaeus 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- 

 ment, 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 

 hypogastric plexus, 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 vesiculae 

 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 coccygaeus muscle, sup- 

 plies it, and terminates on the skin to the side 

 of it. 



The sixth (anterior branch of the coccygaeal 

 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 coccygaeus ; others perforate the 

 ligament, and are lost in the substance of the 

 glutaeus 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 lej-s acute angle, with- 

 out any complex subdivision, as usually 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, 



