THE aim of this paper is to pass in review the more notable advancements in otology, in the departments of anatomy, physiology and bacteriology during a period of about five years past. In the time allotted little can be done but to summarize, and this mode of treatment leaves little room for criticism and none for originality. It is hoped, however, that it will serve its purpose in stimulating discussion, and perhaps, in some instances, encouraging or guiding subsequent reading in some particular direction. To serve this end there will be found appended a very copious reference list of authors and articles. .
ANATOMY.-In this department of otology the growth of knowledge is of necessity slow, even where the work of several years is scanned. Considerable interest has lately attached to the relative situation and course of the lateral sinus, this being a point of vital importance in the surgery of the mastoid region and in brain surgery, which is just now so enthusiastically studied with relation to diseases of the ear. This sinus is now believed to follow a higher and more arching course after leaving the occipital protuberance and before beginning its downward dip behind the meatus, than was previously taught, and also to approach nearer to the meatus in its descent +1.
This changes somewhat the point and method chosen for surgical entrance. To drain the mastoid antrum, for instance, it is recently recommended to use a drill, which must not exceed 1/4 inch in diameter, and enter straight in at a point immediately below the level of the upper border of the bony meatus and as close to its interior wall as possible. Another point which has apparently been established recently is in regard to the location of the auditory centre. This is claimed to be seated in “the posterior third of the first and second temporal convolutions.” The fibres of the auditory nerve from their origin “in the bi- polar ganglionic cells of the cochlea and vestibular ganglia,” +3 proceed upward to these convolutions, and on their way undergo decussation, so that each cerebral hemisphere is supposed to receive impressions from both ears.
The only nerve fibres which find their way into the cerebellum are said to be those which arise from the membranous semi-circular canals +4. This view of the location of the auditory centre-for speech, at least-is corroborated by the finding of two autopsies, since published, in one of which +5 a pre-existing deafness on the left side, without apparent disease of the left ear, is thought to have been accounted for by the location of a cerebral tumor upon the right or opposite side of the brain, by which the first temporal convolution had been destroyed and the second somewhat injured; while the second autopsy +2, in connection with the previous history of the case, seems to demonstrate, in addition, that total deafness only results when the hearing centre is destroyed on both sides of the brain +6.
PHYSIOLOGY.-Perhaps the most interesting of the physiological questions which have received recent discussion, relates to the function of the tympanic membrane, which has acquired a new importance within the past year or two. One view advanced +7 is that its chief function is that of protection of the inner-tympanic structures, its presence especially guarding the membranes of the round and oval windows, and preventing their becoming dry and rigid. The transmission of sound by the drum- head is held to be a function of secondary importance, and the improvement of hearing which often follows and artificial perforation, it is believed can be only temporary because of the absence of the protection which the membrane tympani is designed to afford.
Viewed from another, and purely experimental, standpoint, the function of the tympanic membrane as a transmitter of vibrations certainly seems to be a most important one. By means of some exceedingly ingenious and skilful experiments upon the cadaver, it has recently been demonstrated that if a lateral upon the cadaver, it has recently been demonstrated that if a lateral motions be given to the head of the malleus, a corresponding tilting motion is communicated to the foot-plate of the stapes, causing it to move from side to side in the direction of its long axis; and also, if an outward and inward motion is given to the tympanic membrane and malleus by means of the pneumatic speculum, a similar motion is perceived in the stapedial plate, which is seen to be drawn outwards as well as pushed inwards-a point of departure from all previous views.
This the experimenter +8 speaks of as a “piston movement,” and he thanks it probable, from his experiments, that in some conditions partial or entire mobility may be restored to the stapes. This ready response of the stapedial plate to all movements of the tympanic membrane furnishes the latest explanation +9 of the perception of the direction of sound, since different vibrations are communicated in accordance with the different angle at which sound-waves impinge upon the surface of the membrane.
In regard to the mode of regeneration of the tympanic membrane, a new fact has been ascertained. There seems to be a difference whether the membrane is newly formed in its entirety, beginning at the tympanic ring, or whether it is merely the repair of a perforation. In the former case, it is demonstrated by a recent microscopical examination +10 that the lamina propria is reproduced by fibres, somewhat more dense than normal, which radiate inward from the tympanic ring +11.
One of the most original of recent investigations in the physiology of the ear relates to the function of otoliths +12. It being generally conceded that the perception of turning is acquired through the agency of the semi-circular canals, it is now shown that perceptions of progressive movement and of position in space may well be furnished by the otolithic apparatus. The vestibule is therefore found to be the organ of what is very aptly called the “static sense.” In one series of experiments +13 the otolith was removed from aenophores and subsequent movements watched. These became irregular, and without equilibrium. The name “statoliths” is proposed for these substances instead of otoliths, because of their newly demonstrated function.
Finally, the cochlea has come in for recent investigation, with results which are of no little importance. The destruction of this organ, in whole or in part, in forty guinea-pigs, has demonstrated +14 that total deafness invariably follows complete destruction of the cochlea, and sometimes follows its partial destruction. It is surmised that perception of the higher notes of the musical scale may occur at the base of the cochlea, and the lower tones be perceived at the apex. This view is supported by the result of a recent human autopsy +15. The patient had exhibited total deafness upon both sides, for all sounds except musical notes of low pitch. In the right cochlea was found, at the apex, a few nerves which were fairly well preserved, and Corti’s organs in perfect condition.
BACTERIOLOGY.-This new field of investigation has already been well cultivated, and has been prolific of both facts and theories, the practical importance of which the future alone can determine. All portions of the auditory tract, including the Eustachian tube, the mastoid antrum, and even the interior of the labyrinth and the adjacent meninges of the brain, have been patiently and repeatedly searched for bacteria, and cultures obtained for study and verification.
Also all secretions of the ear, and especially those which are purulent, have been subjected to the same process. Cerumen, for instance, has been searched for the presence of micro-organisms, and one set of experiments +16 covers a series of cultures made from fifty impacted cases. Large numbers of bacilli and cocci of different species were found, and their subsequent injection into animals produced disorders of the liver, lungs, and abdominal glands. But, in this particular instance, no practical deduction seems possible.
Among the curiosities of bacteriology may be mentioned a species of mould removed from the human meatus +17, the spores of which were for the inoculation of rabbits. These died in consequence, presenting characteristic symptoms of nephritis. The mould was therefore named eurotium malignum.
As might be expected, furuncles have received a special share of attention, and have been thoroughly studied with reference to the influence of bacteria. Cultures made from their contents exhibit constantly the staphylococcus albus, aureus or citreus +18, either singly or combined. Experiments with these cultures +19 show that the presence alone of these cocci upon the surface of the skin is not sufficient to cause a furuncle, but that by rubbing they must be made to enter into the skin.
How this entrance is really effected is a subject of interesting controversy, some holding an abrasion of the skin to be necessary, or an entrance by means of the gland ducts +18, while it is claimed by others to be demonstrated by the microscope that the staphylococcus aureus penetrates the skin, not by way of surface-wounds or sweat-glands, but into the hair follicles +20, working down between the hair and the root-sheath.
