370 REPORTS ON THE STATE OF SCIENCE; 



The imiiiediately preceding position may be taken as the measure of 

 auditory acuity of the right car. The procedure is then to be repeated 

 on tlje left side, the right ear being stopped, for the determination of the 

 threshold of auditory acuity of the left ear. 



TACTILE DISCRIMINATION. 



To determine the threshold of local discriininalion of two simultaneous 

 touches on the shin. — The area most suitable for the application of this 

 test is the middle third of the Hexor surface of the left forearm. An 

 asstliesiometer with two ivory points, of which one slides along a milli- 

 metre scale, should be used (Dr. Spearman's pattern is recommended). 



The subject must be comfortably seated, his left forearm bai'ed and 

 supinated and resting upon a pad on the table at a convenient height, while 

 he supports himself by placing his right forearm on the table and across 

 his chest. 



The two points are apjjlied suddenly and simultaneously in a line 

 parallel to the long axis of the forearm, with pressure sufficient distinctly 

 to pit the skin, and continued for about one second. The two points 

 are separated by 80 mm. A series of five applications of the two points 

 at this distance is irregularly interspersed with five applications of a 

 single point. Each contact should be preceded by a warning 'Now.' 

 The subject is instructed to answer ' Two ' or ' One,' according as he 

 judges that he is touched with two points or with one only. He is 

 immediately informed as to the correctness of each answer. If the 

 individual under observation makes no erroneous answers the distance 

 between the two points is reduced to 70 mm., and the series of fi\e 

 double and five single touches is repeated. The same procedure is 

 repeated with two points at 60 mm., 50 mm,, 40 mm., 30 mm., 25 mm., 

 20 mm., 15 mm., 10 mm., 5 mm. When the person being tested gives 

 one or more erroneous replies to double contact in any series of five the 

 series is prolonged to ten double and ten single contacts. A proportion 

 of two wrong answers to eight right in response to the series of ten 

 double contacts is taken as indicating that the distance between the two 

 points is tl.e measure of the threshold of discrimination. If the answers 

 to the double contacts of any one series are to have significance tlie 

 answers to the single contacts of the series must be oftener right than 

 wrong. The answers of the person under observation should be recorded 

 thus ; — 



30 mm ^ ^i"g'*^ touches L/. LL-XX-LX-LL 

 ■ ]_ Double touches LL>^LLLLy^LL 



The answers recorded in this example would indicate that 30 mm. is) 

 the measure of the sensible discrimination of the subject. 



If the individual being tested makes no errors at one step (aay 40 mm.), 

 and breaks down completely at the next step (say 30 mm.), the length 

 midway between the lengths separating the two points in the two cases 

 may be taken as the measure of sensible discrimination. 



MUSCtJLAE POWER. 



To measure power of grip a dynamometer to be obtained from Collin^ 

 8 Rue de I'Ecole de Medecine, Paris, may be used. The subject should 

 squeeze the instrument with the greatest possible effort three times in each 



