=Tuning Fork Test.=—The normal time rate in seconds set of forks is as follows: Fork 32 64 128 512 2048 4096 B. C. 25 30 30 20 10 A. C. tone 70 90 90 40 20 The tuning fork test, carefully made, is the only known method of measuring the functions of the various structures concerned in audition. =The Whisper Test= is made by producing a clear whisper from residual air only, which should be heard about twenty feet by a normal ear. =The Watch Test= is made by using some loud ticking watch (I prefer an Ingersoll), holding it first near the ear until the patient recognizes the tone, and then taking it beyond the hearing distance and approaching the ear until it is heard. I prefer also to move away from the ear until the limit is reached and strike an average of this with the above results. The average eighteen size Ingersoll watch can be heard for from 100 to 150 inches by the normal ear. The practical test for the patient is his hearing from the spoken voice, and is the most reliable so far as permanent results are concerned. =Low Tone Limit.=—The lowest limit of hearing is about sixteen double vibrations per second, but the lowest practical limit is about thirty-two. There are few people with normal hearing and with musically trained ears who can recognize a definite tone lower than this, so I consider the thirty-two fork sufficiently low for all practical tests. =Conduction Deafness.=—Low tones are lost in tympanic involvement or conduction deafness, and are diagnostic in such cases, but are of no particular value in nerve deafness except when that is complicated by catarrhal deafness. =Practical Hearing Limits.=—The human voice varies from about 60 to 150 double vibrations per second, and most sounds that we really need to hear are less than 700 vibrations per second. This is the reason for using the low forks, 64, 128 and 512. =Measurement of Nerve Force.=—To measure auditory nerve force, the fork (say the 128, whose normal B. C. is 30 seconds) is set into vibration and held gently and with even pressure against the mastoid and the patient is asked to tell or signal the doctor when he ceases to hear the tone. Two or more tests may be made to determine the patient’s personal equation, but the use of control forks (the 64 and 512) will show any such error. Granting that there is no complicating pathology, tympanic or labyrinthine, the number of seconds of hearing over 30 will be the patient’s auditory nerve force. For example, if he hears the fork 30 seconds his hearing will be thirty-thirtieths or normal. If his hearing is 25, 20, 15 or 10 seconds, his auditory nerve force will be respectively 25-30, 20-30, 15-30 or 10-30.