SPECIAL SENSATIONS. 391 



of in/nervation)^ It is, however, probable that this sensa- 

 tion, by means of which we are made aware of the degree of 

 contraction of our muscles (sense of muscular activity, Gerdy) 

 is the same as that which causes the sensation of fatigue 

 which follows moderate but long-continued exercise, and 

 that its seat lies in the contracted "fibres, while the sensation 

 of fatigue experienced after violent exertion appears to reside 

 principally in the tendons (Sappey). 



II. SPECIAL SENSATIONS. 



THE special sensations render us conscious of external 

 bodies, and of their various properties. They are furnished 

 by the organs of the senses, each of which supposes, 1, an 

 organ susceptible to the impression ; 2, a nerve, by means of 

 which the impression is transmitted ; and 3, a central part of 

 the brain by which the impression is received and under- 

 stood. 



The peripheral organ, which first receives the impression, 

 proceeds always from a more or less modified part of the 

 cutaneous and external surface (epidermis), or of the most 

 primitive parts of the internal surface (epithelium) : thus we 

 have, as organs of the senses proceeding from the skin, the 



1 See also researches by Bernhardt (Zur Lehre von Muskelsinn. 

 Analyse, en " Revue des Sciences Medicales," de G. Hayem. Vol. 

 I. p. 61, 1873). This author holds, with J. Miiller, Ludwig, and 

 Bernstein, that the muscular sense simply consists in the faculty of 

 exactly estimating the intensity of the excitation which, beginning 

 in the encephalon, results in the movement intended. He found, 

 after causing the contraction of the muscles by faradization (the 

 interrupted current) that the person experimented upon experienced 

 much greater difficulty in recognizing the variation between differ- 

 ent weights than when the contraction was produced by the influ- 

 ence of the will. From this Bernhardt concluded that the sense 

 of force is a psychical function < He admits, however, that the sen- 

 sory impressions beginning in the soft parts adjacent to the muscles 

 have a powerful influence in completing the notion or idea formed 

 by the centres of volition. According to him, therefore, the mus- 

 cular sense, properly so called, has no existence. Trousseau, con- 

 sidering the subject from a similar point of view, has also denied 

 the existence of the muscular sense, referring every thing to the 

 sensibility of the soft parts displaced by the movement. See Art. 

 Alaxie, en " Nouv. Diet, de Mod. et de Chir. Prat'." VD!. HI. 

 p. 770.) 



