io22 THE MUSCULAR SENSE. 



24 grms. The static leverage being taken into account, the observations 

 indicate that the delicacy of perception of resistance as measured by the 

 minimum perceptible is greater for peripheral than for proximal segments of 

 the limb. 



Liminal difference. — H. E. Weber, measuring the just noticeable difference 

 between weights successively lifted by the same arm, found that difference 

 one-fortieth part of the lesser of the two weights compared. The law which 

 he had previously induced from observations on tactile stimuli, he therefore 

 recognised as applicable to the muscular appreciation of resistances. That 

 law states that the increase of stimulus required to be perceptible as an 

 increase is not any fixed quantity, but one that bears a constant ratio to the 

 total stimulus. 



Weber's observations on the application of his law to kinsesthetic sensa- 

 tions rest on experiments that deal with only a small number of compared 

 weights. He attempted to exclude participation of touch in the discrimination 

 by hanging the weight in a cloth, the gathered ends of which were compressed 

 as tightly as possible between the fingers. In that way he sought to keep 

 the tactile stimulus maximal and invariable throughout. Since then fuller 

 series and stricter methods have been pursued. Fechner in his historical 

 research 1 recorded 24,576 separate judgments on weights of vessels, which 

 could be filled in various degree and lifted each by a wooden handle. Hitzig's 2 

 kinaesthesiometer has been frequently employed ; it is a set of balls outwardly 

 alike, but individually loaded so as to be of different weights. Merkel 3 used 

 pressure on a balance-beam ; Jacobi 4 preferred a form of steel-yard, one end 

 of which was lifted by the hand. Goldscheider 5 employed a weight attached 

 by a cord running over a pulley. Langlois and Richet 6 observed as index to 

 the fineness of the muscular sense in the respiratory mechanism, the smallest 

 rise in the mercury column of a manometer which caused perceptible im- 

 pediment to the expiration of the observer. 



The observations obtained by these methods can be dealt with by — (1) 

 The methods of just discernible differences ; (2) the method of average error ; 

 (3) the method of right and wrong answers ; (4) the method of intervals 

 apparently equal ; or (5) the method of doubling the stimulus. These 

 methods have been already alluded to. 



In Jacobi's observations, 7 the liminal difference remained pretty constantly 

 oV throughout a long range of weights. Experiment finds, in fact, that in 

 the muscular, as in the other senses, the liminal difference is not expressible 

 throughout the range of even work-a-day stimuli as a constant fraction of the 

 total stimulus. Experiments in Hering's laboratory 8 on the liftings of eleven 

 weights, ranging from 250 to 2750 grms., showed the liminal sensible increment 

 to vary from ^ T at 250 grms. to T j ¥ at 2500 grms. ; at 2750 grms. to rise 

 to Jy again. Merkel found that for weights below 200 grms. and above 

 2000 grms., and moved by the finger, the discriminative power was less than 

 for the range between those figures. On the contrary, neither Fechner, 9 

 nor Midler and Schumann 10 found the discriminative delicacy decline with 

 weights even far heavier than 2 kilos. 



1 Ber. d. k. sachs. Gesellsch. d. Wissensch., Leipzig, 1860, S. 76. The vessels used are 

 still in the University, Gottingen. 



2 Neurol. Centralbl., Leipzig, 1888, Bd. vii. 



3 Op. cit. 



4 Arch./, exper. Path. u. Pharmakol., Leipzig, 1893, Bd. xxxii. S. 49. 



5 Arch. f. Physiol., Leipzig, 1891. 



6 Rev. phil., Paris, 1890, p. 557. 



7 Arch. f. exper. Path. u. Pharmakol., Leipzig, 1893, Bd. xxxii. S. 49. 



8 Sitzungsb. d. math.-phys. CI. d. k.-bayer. Akad. d. Wissensch. zu Alihnchcn, 1875, Bd. 

 lxxii. Abth. 3, S. 342, etc. (Hering's own experiments and those of his pupils, Biedermann 

 and Loewit; agree.) 



9 Op. cit. 



10 Arch./, d. ges. Physiol., Bonn, 1889, Bd. xlv. 



