ioi4 



THE MUSCULAR SENSE. 



provided by " muscular sense." Posture, passively maintained, is found 

 to be nearly as accurately perceived as when actively maintained. 

 Sense of posture is very defective in limbs the sensory nerve roots of 

 which are diseased. The appreciation of difference between postures of 

 the limb is not so delicate as to account for the minute alterations — 

 less than an angular degree — at a joint perceived in Goldscheider's 

 experiments. There the perception is one of movement rather than of 

 successive assumption of different postures, — an important distinction, 

 paralleled in the visual and tactual senses. 



Besides purely muscular, articular sensations also probably contri- 

 bute to perception of posture. This has been said 1 to be shown by the 

 position of the fingers being as sensible when the muscles are paralysed 

 as when they are normal, — but in reality such observations fail to prove 

 or negative the assertion. 



Perception of passive movement. — The minimal adequate stimulus 

 for sense of passive movement may be expressed in angular measurement 

 of a movement about a joint. Leyden found that movements of - 5° to 1° 

 at the hip-joint are perceptible ; 2 but we owe most of the measurements 

 on this subject to the careful work of Goldscheider. 3 The liminal 

 excursion for the shoulder-joint is -2° to -4°, the speed of movement not 

 being less than -3° per second. Degree of sensitivity, as judged by the 

 size of the liminal excursion, places the joints in the following order, 4 

 beginning with the least sensitive : — 



Arranging the joints in order of speed of movement required for the 

 limen of perceptible excursion, the list is as follows, 4 beginning with the 

 least sensitive : — 



First phalangeal joint . 



Wrist. 



Metacarpophalangeal . 



Ankle 



Hip . 



Knee .... 



Elbow 



Shoulder 



12° *5 per second. 

 3°-9° 



4° 



2°-3°-5 

 l°-6-3°-2 „ 

 l°-2°-5 



0°-7-l°-4 „ 

 0°-3-l° 



A much smaller (]-), and especially a much slower ( T V), movement 

 is just noticeable at the great proximal joints of the limb than at the 

 small peripheral. The delicacy of sense of movement progressively 



1 Duchenne, "Conscier.ee musculaire," Paris, 1853. 



2 Virehoivs Archiv, 1869, Bd. xlvii. S. 32. 



3 Goldscheider excluded cutaneous sensations of pressure, as far as possible, by casing 

 the segment of the limb in a gutta-percha sheath filled with water. The limb was moved 

 by hydraulic means, and the movement was recorded graphically on a magnified scale 

 upon a rotating cylinder, so that its time and its amplitude of excursion were known. 



4 Goldscheider, Arch. f. Physiol., Leipzig, 1889. 



