i»,nn«m>w iin.ni>, ii • lj.large action potentials which often amount to 30 mV. Actually the attempt to record such single fiber responses from the auditory nerve turned out to be successful* The results obtained indioated that the nerve fibers arising in the basal turn reapond to all the frequencies examined (between £00 and 10,000 ops) at sound levels of about 50 db above 0*0002 nlorobar» Unlike teas cell-body responses from ths ooahlear nucleus, none of the spontaneous discharges observed In

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... these primary p sensory neurons wore ever inhibited by sound stimulation* The synopsis of this work was presented in the Spring Meeting of the American Physiological Society in 1953 (20). I i £ i in _yttQ l *i-. s -METHODS Surpical operation* Guinea pics were anaesthetised with Dial in ure thane (0*5» ecu/kg* body weight)* An incision was made through the skin along the mas so tor muscle* After ligating the external jugular vein both the masseter muscle and the mandible were out across in the mldd&e* and the posterior half of the mandible was removed* By lifting the posterior part of the masseter muscle, the bulla was then exposed* Hoxt all the tissues around the styloid process were carefully separated from the surface of the bone and the process was out across, with a dental drill, as close to its base as possible* After cleaning the surface of the bulla a large opening was made in the bulla to expose the cochlea, the ossicles and the tympanic membrane* Then, with a small dental drill (size 1/2). a small hole approximately 1 mm* in diameter was made toward the modiolus through the thick bone bounded by the soala tympani of the cochlea, the vestibule and the cerebral cavity* Tliis hole was started on the edge of tfre bulla at the point approximately 3*S> mm« away from the round window* and at the depth of approximately 2 n»a & it reached the modiolus* The histologlcal specimen shown in Fig« 1 | "hows the position and the direction of the hole* The surface of the acoustic nerve was then cleaned with a sharp needle and forceps* All these operations were duu»