THE MUSCULAR SENSE. POWER-SENSE. 937 



there results the recognition of the temporary position of the extremities. 

 Some muscles, for example the respiratory muscles, possess only slight 

 muscular sensibility, which seems to be absent normally from the heart 

 and unstriated muscles. 



Method of Testing. Weights are wrapped in a cloth and are suspended from 

 the part to be tested (for example the leg) by a sling. The subject estimates 

 the amount of the weight by lowering and raising it; and also the difference in 

 resistance (of the weights), as well as the minimum of resistance (appreciation of 

 the smallest weight). The electro-muscular sensibility also may be tested by 

 causing the muscles to contract by means of induction-currents and having the 

 subject report as to the sensation thereby produced. In this way also the mini- 

 mum of sensibility and of pain can be determined. 



A healthy person recognizes a weight of i gram applied to his upper extremity ; 

 likewise an addition of one gram when the original weight was 15 grams, an addi- 

 tion of two grams when the original weight was 50 grams; and an addition of 3 

 grams when the original weight was 100 grams. The power-sense differs in 

 different fingers. The lower extremity (with the weight suspended from the 

 knee), recognizes from 30 to 40 grams; but often only a heavier weight. Often, 

 a difference of from 10 to 20 grams can be detected, or from 30 to 70 grams. In 

 general, the same differences are detected whether the original weights are light 

 or heavy. In blind persons the muscular sense is often heightened. 



Section of the sensory nerves causes derangement of the fine grada- 

 tions of movements. Meynert supposed that the motor cortical centers 

 represented the cerebral center for the muscular sense, the muscles being 

 connected by motor and sensory paths with the ganglion-cells in these 

 centers. Support is given this view by the occurrence of complete 

 ataxia as a result of destruction of those areas in which the psychomotor 

 cortical centers of the extremities are situated. 



Illusions occur in the range of the muscular sense. A weight held 

 by one limb appears to become lighter as soon as other muscles of the 

 limb are contracted, although these do not themselves aid in supporting 

 the weight. Under converse conditions the weight appears to be 

 heavier. If equally heavy objects of different size are lifted, the larger 

 appear to be the lighter. A weight raised with both hands seems 

 lighter than when raised with one hand. The following illusion has 

 been observed with respect to the muscular sense of the tongue. If 

 the tip of the tongue is pressed against a narrow interval between the 

 teeth, and is moved to and fro, there results a feeling as if the teeth 

 yielded in movement. 



Excessive muscular activity causes the sensation of fatigue, of 

 oppression and weight in the limbs, which is referable to the muscular 

 sense. 



Pathological. Abnormal heightening of the muscular sense is rare (muscular 

 hyperalgia and hyperesthesia) . It occurs in the distressing condition of unrest 

 designated anxietas tibiarum (fidgets), which is attended with continual change 

 in the position of the limbs, and not rarely may be a source of annoyance even 

 to healthy persons at night. Cramp is a condition attended with intense pain 

 as a result of irritation of the sensory nerves of the muscles; it occurs also in 

 association with inflammatory processes. Impairment of the irritability of the 

 nerves of muscular sensibility appears also in part to be responsible for certain 

 choreic and ataxic movements. In tabetic patients the muscular sense in the 

 upper extremities may be normal or diminished; in the lower extremities it is 

 usually considerably diminished. Occasionally, the electromuscular sensibility 

 is impaired or even lost; in other cases the subjective sense of muscular activity 

 is lost (paralysis of muscular consciousness). Adequate doses of cocain or alco- 

 hol are capable of heightening the muscular sense, while amyl nitrite blunts it. 



