SENSORY GANGLIA IN VOLUNTARY MOVEMENT. G71 



side or to the other, we feel that we can do so but very imperfectly, and with 

 a sense of effort referred to the muscles themselves, this sense being the 

 result of the state of tension in which the muscles are placed by the effort 

 to move the eyes without the guiding visual sensation. Now, on the other 

 hand, the Will may determine to fix the eyes upon an object; and yet this 

 very fixation may be only attainable by a muscular movement, which move- 

 ment is directly excited by the visual sense, without any exertion of volun- 

 tary power over the muscles. Such is the case when we deterrainately look 

 steadily at an object, while we move the head horizontally from side to side ; 

 for the eyeballs will then be moved in the contrary direction by a kind of 

 instinctive effort of the external and internal recti, which tends to keep the 

 retinae in their first position, and to prevent the motion of the images over 

 them. So, when we look steadily at an object, and incline the head towards 

 either shoulder, the eyeballs are rotated upon their antero-posterior axis 

 (probably by the agency of the oblique muscles) apparently with the very 

 same purpose, that of preventing the images from moving over the retinae 

 (see chap, xv, sect. 3). Now we cannot refuse to this rotation any of the 

 attributes which really characterize the so-called voluntary movements; and 

 yet we are not even informed by our own consciousness that such a move- 

 ment is taking place, but know it only by observation of others, or by the 

 reflection in a mirror. 



542. The muscular contractions which are concerned in the production of 

 Vocal tones, are, in like manner, always accounted voluntary ; and yet it 

 is easy to show that the Will has no direct power over the muscles of the 

 larynx. For w r e cannot raise or depress the larynx as a whole, nor move 

 the thyroid cartilage upon the cricoid, nor separate or approximate the 

 aryteuoid cartilages, nor extend or relax the vocal ligaments, by simply 

 willing to do so, however strongly. Yet we can readily do any or all these 

 things, by an act of the Will exerted for a specific purpose. We conceive 

 of a tone to be produced, and we ivill to produce it ; a certain combination 

 of the muscular actions of the larynx then takes place, in most exact 

 accordance with one another ; and the predetermined tone is the result. 

 This anticipated or conceived sensation is the guide to the muscular move- 

 ments, when as yet the utterance of the voice has not taken place ; but 

 Avhilst we are in the act of speaking or singing, the contractile actions are 

 regulated by the present sensations derived from the sounds as they are pro- 

 duced. It can scarcely but be admitted, then, that the Will does not 

 directly govern the movements of the Larynx ; but that these movements 

 are immediately dependent upon some other agency. 



543. Now what is true of the two preceding classes of actions, is equally 

 true of all the rest of the so-called voluntary movements ; for in each of 

 them the power of the Will is really limited to the determination of the 

 result; and the production of that result is entirely dependent upon the 

 concurrence of a "guiding sensation," which is usually furnished by the very 

 muscles that are called into action. It is obvious, therefore, that we have 

 to seek for some intermediate agency, which executes the actions determined 

 by the Will ; and when the facts and probabilities already stated are duly 

 considered, they tend strongly in favor of the idea that even voluntary 

 movements are executed by the instrumentality of the Automatic apparatus, 

 and that they differ only from the automatic or instinctive in the nature of 

 the stimulus by which they are excited, the determination of the Will here 

 replacing, as the exciting cause of its action, the sensory impression which 

 operates as such in the case of an instinctive movement, and which is still 

 requisite for its guidance. 



544. This view' of the case derives a remarkable confirmation from the 



