endolymph; according to Waldeyer there are about six thousand rods in the inner row, and four thousand five hundred in the outer; a nucleated mass of protoplasm occupies the angle between the base of each rod and the basilar membrane; the Hair cells (Fig. 115) are epithelial cells with stiff hair-like ciliaß disposed in three or four rows upon the superior surfaces of the outer rodsm to the number of about eighteen thousand, and in a single row upon inner rodscd numbering about thirty-three hundred; the Lamina reticularis (Fig. 115) is formed of several rows of small fiddle-shaped cuticular structures called phalanges, connected together and to heads of outer rods, forming ringsmno, through which project the hairs of the outer hair cells. FIG. 115. d Where does the auditory nerve arise and to what parts of the ear is it distributed? Its superficial origin is from groove between olivary and restiform bodies at lower border of pons; its deep origin is threefold (1) from superior vermiformis process of cerebellum, and from (2) inner and (3) outer auditory nuclei formed chiefly by gray substance of posterior pyramid and restiform body, from which latter it receives fibres as it winds around it. Entering with facial nerve the internal auditory canal, at its bottom it divides into the cochlear and vestibular branches, both of which contain numerous ganglion cells; the Vestibular division divides into three branches, the superior splitting into many filaments which pass through upper back part of bottom of meatus, enter the vestibule through macula cribrosa to be distributed to utricle and ampulla of external and superior semicircular canals; the middle branch passes through the openings of the fovea hemispherica to supply the saccule; the inferior passes to ampulla of posterior semicircular canal; the Cochlear nerve divides into numerous filaments at base of modiolus which enter its canals, pass between the two plates forming the lamina spiralis, forming a plexus which contains ganglion cells, and sends branches, it is thought, to communicate with the hair cells; the Intumescentia ganglioniformis Scarpe is the gangliform swelling on the vestibular branch in the internal auditory canal; the Ganglion spirale is the gangliform enlargement on the cochlear nerve as it occupies the canalis spiralis modioli. Give the arterial supply of the labyrinth? The internal auditory, a branch of basilar artery, enters with nerve the internal auditory canal, there to divide into a vestibular and cochlear branch; the Stylo-mastoid, from posterior auricular; occasionally What is the internal auditory canal? A canal about one-third of an inch long, passing outward from posterior surface of petrous portion of temporal bone to end in a cribriform partition perforated with numerous foramina, some of them arranged in a spiral-shaped depression, the Tractus spiralis foraminulentus, others in three groups in as many depressions; at the upper part is the commencement of the aquæductus Fallopii for the seventh or portio dura nerve. Anatomy of Inguinal Hernia. What is the inguinal canal? The canal passing downward and inward for one and a half inches which lodges the spermatic cord in the male, the round ligament in the female, pursuing a course parallel to Poupart's ligament through or between the abdominal muscles, commencing at internal abdominal ring and terminating at the external abdominal ring. 8 Describe the internal abdominal ring. It is an ovoidal opening in the transversalis fascia midway between anterior superior iliac spine and spine of pubes, and about half an inch above Poupart's ligament. It is bounded above and externally by arched fibres of transversalis muscle1o, below and internally by epigastric vessels13; from its circumference passes the infundibuliform fascia on to the spermatic cord or round ligament. What is the external abdominal rings? An obliquely triangular opening in the aponeurosis of external oblique muscle1, just above and to outer side of crest of pubes; from base to apex it averages one inch by half an inch transversely. It is bounded below by the crest of pubes, above by the curved t."aponeurotic intercolumnar fibres, and on each side by the free borders of the aponeurosis called the internal and external columnsz of the ring; from the margins of the ring passes on to the cord or round ligament, the intercolumnar fascia. Give the boundaries of the inguinal canal. Anteriorly, the skin, superficial fascia, aponeurosis of external oblique, and outer third of internal oblique muscles. (upt Posteriorly, the triangular ligament, conjoined tendon" of internal oblique and transversalis muscles, transversalis fascia13, subperitoneal fat, and peritoneum. Superiorly, the arched fibres of internal oblique1o and transversalis muscles. Inferiorly, the union of the transversalis fascia13 and Poupart's ligament. What is Poupart's ligament? The infolded, thickened margin of aponeurosis of external oblique muscle, extending from anterior iliac space to spine of pubes, from which it is reflected a short distance along the pectineal line, forming Gimbernat's ligament, while a triangular band of tendinous fibres attached by its apex to the reflected portion of Poupart's Pila ligament along the pectineal line, passing inward beneath spermatic cord behind the inner pillar in front of the conjoined tendon, and interlacing with its fellow at the linea alba, is called the triangular ligament: the lower part of Poupart's ligament forms the external pillar of the external abdominal ring. Describe the relations of the epigastric artery and the internal abdominal ring. It passes between the transversalis fascia and the peritoneum along the lower inner margin of internal ring beneath the spermatic cord. What is the cremasteric fascia ? A series of muscular loops connected by areolar tissue investing the spermatic cord, supposed to have been derived from the internal oblique muscle during the descent of the testicle, and, of course, absent in the female. What is Hesselbach's triangle? A triangular space at lower part of inner surface of abdominal wall, bounded externally by the epigastric artery, internally by margin of rectus muscle, and below by Poupart's ligament: the conjoined tendon stretches across the inner two-thirds of this space, the remainder being filled in by the transversalis fascia. What is an oblique inguinal hernia? A protrusion of bowel, omentum, or both, following the course of the spermatic cord in the inguinal canal through both internal and external rings (when complete), the neck of the sac being to outer side of epigastric artery. What are the coverings of an oblique inguinal hernia? Skin; superficial fascia; intercolumnar fascia; cremaster muscle12; infundibuliform fascia; subserous cellular tissue; and peritoneum forming sac. Where is the seat of stricture most apt to be? (1) At internal ring, (2) inguinal canal by fibres of internal oblique or transversalis muscles, (3) at external ring, provided it is not at thickened neck of sac, the most usual site in old hernia. What is a direct inguinal hernia? One where the protrusion passes through some part of Hesselbach's triangle, passing directly through the external abdominal ring, the neck of the sac being internal to the epigastric vessels. What coverings has a direct hernia?ame w. difs. The same as an oblique, except that the transversalis fascia take the place of the infundibuliform fascia, and the conjoined tendon is substituted for the cremasteric fascia, but this latter covering is probably a theoretical, not an actual one. Femoral Hernia. Describe the femoral or crural canal. It lies beneath Poupart's ligament, to inner side of femoral vein1o, extending from femoral ring above to saphenous opening" below: it is about half an inch long, closed above by the septum crurale, formed of condensed areolar tissue, and below by the cribriform fascia, a portion of the deep layer of the superficial fascia covering the saphenous opening: the Femoral or crurat ring is an oval space between femoral vein and Gimbernat's ligament, half an inch in diameter, larger in female |