THE VOICE. 819 



ing muscle on its attachments ; and undoubtedly in many instances of cramp, 

 the pain is chiefly felt at the joints ; and, as we know, Pacinian bodies are 

 abundant around the joints. Afferent nerves, however, having a different 

 disposition from the ordinary motor nerves which terminate in end-plates, 

 have been described as present in muscle ; and analogy would lead us to sup- 

 pose that these afferent fibres, though possessing a low general sensibility, 

 might be easily excited in a specific manner by a muscular contraction ; but 

 further investigations are necessary before these can be accepted as the true 

 nerves of the muscular sense. 



752. In favor of the view that the muscular sense is peripheral and 

 not central in origin may be urged the fact that the sense is felt when the 

 muscles are thrown into* contraction by direct galvanic stimulation instead 

 of by the agency of the will. Many authors, while admitting the existence 

 of a muscular sense of peripheral origin, contend that we also possess and 

 are very largely guided in our movements by what might be called a 

 " neural " sense of central origin. That is to say, the changes in the central 

 nervous system involved in initiating and carrying out a movement of the 

 body so affect our consciousness that we have a sense of the effort itself. 



It has been observed that when the posterior roots are divided, move- 

 ments become less orderly, as if they lacked the guidance of a muscular 

 sense ; and although the impairment of the movements may be due in part 

 to the coincident loss of tactile sensations, it is probable that it is increased 

 by the loss of the muscular sense. There is a malady or rather a condition 

 attending various diseased states of the central nervous system called loco- 

 motor ataxia, the characteristic feature of which is that, though there is no 

 loss of direct power over the muscles, the various bodily movements are 

 effected imperfectly and with difficulty, from want of proper coordination, 

 In such diseases the pathological mischief is frequently found in the posterior 

 columns of the spinal cord and the posterior roots of the spinal nerves, that 

 is, in distinctly afferent structures ; and the phenomena seem in certain cases 

 at least to be due to inefficient coordination caused by the loss both of the 

 muscular sense and of ordinary tactile sensations. The patients walk with 

 difficulty, because they have imperfect sensations both of the condition of 

 their muscles and of the contact of their feet with the ground. In many 

 of their movements they have to depend largely on visual sensations ; hence 

 when their eyes are shut, they become singularly helpless. In other cases 

 again ataxia may be present without any impairment of touch ; but a dis- 

 cussion of the varied phenomena of this class of maladies cannot be entered 

 into here. 



CHAPTER VI. 



SPECIAL MUSCULAR MECHANISMS. 

 THE VOICE. 



753. [THE larynx is a membrane-cartilaginous chamber, broader above 

 than below, and situated in the anterior median portion of the neck. It 

 consists of a number of cartilages, which are articulate with each other, 

 connected by ligaments, moved by a number of muscles, and lined by a 

 mucous membrane. 



