PROFESSOR ALISON ON THE NERVES OF THE EYEBALL. 87 



destined solely to convey the influence of sensation and emotion downwards to the 

 organs of organic life, these nerves are every where bound up in the same sheath 

 with the nerves of common sensation, by which impressions are carried upwards 

 to the brain. 



Thus the study of the nerves of the eyeball enables us, I think, to give a de- 

 cided opinion as to the following points : 



1. That all strictly animal muscular movement is not only excited, directly 

 or indirectly, by Sensations producing it, but is continually guided and regulated 

 by sensations which succeed and result from it. 



2. That it is the province of these resulting sensations, commencing or anti- 

 cipated, to determine on individual muscles the influence of the Will ; and where 

 distinct annual movements are always consentient, it is because the sensations 

 thus guiding them are the same. 



3. That neither the connections of nerves at their roots (so far as anatomy 

 has detected them), nor the Plexuses which they form in their course, can be 

 assigned as the cause of consentience of their movements, or of any combinations 

 of their actions ; but that the plexuses of nerves, placing both the sentient and 

 motor nerves of the muscles of the extremities in connection with a large surface 

 of the spinal cord, seem to be designed and fitted to render the muscular sensations 

 more distinct, and the acts of the will more energetic than they otherwise would 

 have been, and thereby to give power, facility, and precision to the combinations 

 and successions of muscular contractions in all movements of the limbs. 



4. That the action in nervous matter which is excited by an act of the will, 

 can traverse a Ganglion, but is never felt to be exercised, and therefore cannot be 

 applied to any specific object, beyond it, apparently because of a modification of 

 the endowments, both of sensitive and motor filaments of nerves, where they are 

 subdivided and intermixed with the grey matter of a ganglion. 



5. That the motor filaments of nerves which have passed through ganglia 

 may be affected by changes in the sensitive as well as the motor filaments which 

 enter the ganglia ; and that in this way, probably, the influence of sensations and 

 emotions of mind (which must be transmitted through the ganglia, because it 

 affects especially muscles which have only ganglionic nerves) is conveyed from 

 many parts of the spinal cord, and concentrated on the muscles of organic life. 



6. That the influence of changes in the nervous system, and especially of 

 such as accompany sensations and emotions of mind, on the capillary circulation, 

 on the functions of nutrition and secretion, and on the properties of the blood, 

 may be transmitted downwards by the nerves of common sensation, and that it 

 is probably with a view to this influence that the ganglia are formed on the roots 

 of those nerves. 



VOL. XV. PART I. A a 



