390 ORGANS OF THE SENSES. 



of the muscles), but the muscular sense is none the less an 

 indisputable fact. 1 Cl. Bernard has made it certain by vari- 

 ous experiments : if all the cutaneous nerves of the lirnb of 

 an animal be cut, the skin is rendered completely insensitive, 

 although the animal still continues to walk tolerably well, 

 probably because the muscular sensibility is preserved. If 

 the posterior roots (that is, all the sensory nerves, muscular 

 and others) are cut, instead of the cutaneous branches, the 

 movements made by the animal become much less steady. 

 In cases of extensive paralysis in man, when the sensory 

 branches of the muscles are implicated, the patient appears 

 to move his limbs with difficulty, and to be able to do so, 

 only when watching them so as to direct their movements 

 (Cl. Bernard). Finally, some pathological observations have 

 been made in which paralysis of the muscular sense was ob- 

 served, while the sensibility of the skin remained, or vice 

 versa (Landry, Axenfeld). This sensibility, or rather mus- 

 cular sense, enables us to judge of the force and extent of our 

 movements : we judge of their force by distinguishing the 

 difference between different weights, raised one after the 

 other, provided that the variation in the weight of each be 

 at least -^ (Weber) ; and it is remarkable that the sensibility 

 for lifting weights is much more acute than for the pressure 

 produced by such weight (see farther on, sense of touch) ; 

 this proves once more that the sensibility of the muscles is 

 entirely distinct from that of the skin. 



The study of the muscular sense is still, however, wrapped 

 in such obscurity that some authors (Trousseau) have entirely 

 denied its existence, while others differ greatly in their 

 opinions respecting it : thus Wundt maintains that " the seat 

 of the sensations of motion appears to lie, not in the muscles 

 themselves, but rather in the motor-nerve cells (of the ante- 

 rior gray matter of the spinal axis), since we experience not 

 only the sensation of a movement performed, but also that 

 of one which has been only intended : the sensation of move- 

 ment thus appears to be directly connected with motor inner- 

 vation" (for which reason Wundt designates it as the sensation 



1 See Duchenne (de Boulogne), " De 1'Electrisation Localisee," 

 p. 389. Paris, 1872. 



Cl. Bernard, " Leons sur la Physiologic et la Pathologic du 

 Syst. Nerveux." Vol. I. p. 246. 



Jaccoud, " Les Paraplegies et 1'Ataxie du Mouvement." Paris, 

 1831. 



