the Helmholtz theory has received confirmation on the pathological side by the discovery that, in certain individuals, the hearing, of tones is abrogated over a definitely circumscribed portion of the scale (tonal gap), or is abrogated in general, but retained over a similarly circumscribed area (tonal island) — facts that accord admirably with the functions ascribed hypothetically to the strings of the basilar membrane. Vivisectional experiments on dogs seem to show that excision of the tip of the cochlea (where the membrane is widest) produces a deafness to bass tones; but confirmation of this is required.
In spite of its explanatory powers, the Helmholtz theory has never lacked opponents. Various objections have been urged against it; as, that the theory, in assuming that the ratio of width of the two ends of the basilar membrane is about 1:12, greatly overstates the triangularity of the membrane: that the membrane is too closely woven for its radial fibres to vibrate, even in small batches, not to speak of the separate vibration of single fibres: that the structures of the cochlea are too minutely small for the strings to act as resonators to the deep tones which audition can distinguish; and so on. Hence, a number of theories have arisen which reject the idea of resonance altogether, and assume that the basilar membrane vibrates in one piece. Waller's theory, which we may take as typical of this direction of thought, is formulated as follows: the basilar membrane is 'a long, narrow drumhead, repeating the complex vibrations of the membrana tympani.' It "vibrates in its entire area to all sounds (although more or less in some parts than in others), giving ... acoustic pressure-patterns between the membrana tectoria and the subjacent field of hair-cells. In place of an analysis by consonation of particular radial fibres, ... varying combinations of sound give varying pressure-patterns, comparable to the varying retinal images of external objects." No one of these opposing theories has been worked out in any considerable detail. (See Ear; Acoustics; Psychological Apparatus.) Consult: Helmlioltz, On the Sensations of Tone (Eng. trans., London, 1895); Ebbinghaus, "Psychologie," in Zeitschrift für Psychologie (Hamburg, 1897-1902); Waller, Introduction to Human Physiology (New York, 1891).
AU'DITOR (Lat., hearer, from audire, to hear). At common law, an officer appointed by the court in the action of account or account render to take and state the items of debit and credit between the parties to the action, determine the balance due, and report to the court.
Similar officers were appointed in chancery, who were more usually known as masters in chancery. (See Master in Chancery.) As the common-law action of account fell into disuse, courts of common law ceased to appoint auditors; but under modern statutes, the law courts have power to appoint officers exercising quasi-judicial functions in the taking of accounts, taking of evidence, trial of issues, etc., variously known as auditors, commissioners, or referees. (See Commissioner; and Reference.) Their reports, when filed and confirmed, form the basis of the judgment rendered by the court. The powers and duties of such officers are, in general, limited and defined by the statutes authorizing their appointment.
The term auditor, as now employed, however, more commonly has reference to two classes of persons, usually expert accountants, who have increased in numbers to meet the demands of the growing importance and complexity of industrial and financial affairs, and who perform the service of examining and slating the accounts of Government departments, corporations, and private concerns. Many of our large cities, as well as the State and general governments, have official auditors (called, in New York City, commissioners of accounts) as a part of the regular administrative machinery; and the same is true of many of the larger industrial corporations. Private auditors are ordinarily subject to no legal regulation, except such as is imposed by the contract under which they are employed, and the general obligation to exercise a reasonable degree of skill, care, and caution. A higher degree of skill is required of a professional auditor than of one who does not hold himself out as an expert; such skill, in fact, as is exacted of all strictly professional men. In some of the States of the United States a class of public accountants, licensed and registered by the State, is recognized by statute. For the law as to auditors under the English Companies' Acts and other acts, consult Pixley, Auditors: Their Duties and Responsibilities, 7th ed. (London, 1896).
AU'DITORY, or EIGHTH, NERVE. According to the older nomenclature, the portio mollis of the seventh pair. The nerve connected with the special sense of hearing. The apparent origin of this nerve is from the ventro-lateral surface of the medulla immediately behind the transverse fibres of the pons. Of the two distinct bundles of fibres that can be distinguished in it, one (the cochlear division) passes to the outer side of the restiform body, or inferior peduncle of the cerebellum, while the other (the vestibular division) passes to the inner side of the restiform body. The fibres terminate in three nuclei. Of these, two are situated in the gray matter of the fourth ventricle, and are known respectively, from their positions, as the median nucleus and the lateral nucleus of the eighth nerve. The third, or accessory nucleus, is a group of cells just ventral to the restiform body at the point of convergence of the two roots. The fibres of the cochlear division of the nerve are the axones of cells situated in the spiral ganglion, or ganglion of Corti; these cells are bipolar, and their peripheral, termination is, in Corti's organ, situated within the bony cochlea, the ends of the fibres of the cochlear division mainly in the lateral nucleus. The fibres of the vestibular division of the nerve are the axones of cells situated in Scapa's ganglion of the internal ear: these cells are also bipolar, their peripheral terminations being among the hair-cells of the crista and macula acustica in the vestibule and semi-circular canals; the ends of the fibres of the vestibular division are mainly in the median and accessory nuclei. By means of neura, whose cell-bodies are situated in these nuclei, auditory impressions are transmitted to higher centres.
