31 8 ON THE PRESENT STATE OF KNOWLEDGE 



excluded from any influence upon the action of the nervous matter, 

 which must be regarded as a substance exhibiting certain phenomena, 

 whose laws are as much a branch of physical inquiry as those 

 presented by a magnet. 



Xow (still carefully excluding the phenomena of consciousness), 

 we shall find on careful examination, that all the properties of Nerve 

 are of the same order as those exhibited by the nervous substance of 

 the heart. Every action is a muscular action, whose proximate cause 

 is the activity of a nerve, and as the muscles of the heart are related 

 to its ganglia, so are the muscles of the whole body related to that 

 great ganglionic mass which constitutes the spinal marrow, and its 

 continuation the medulla oblongata. This cranio-spinal nervous 

 centre originates and co-ordinates the contractions of all the muscles 

 of the body independently of consciousness, and there is every reason 

 to believe that the organ of consciousness stands related to it as the 

 pneumogastric is related to the cardiac ganglia ; that volition whether 

 it originates, or whether it controls action, exerts its influence not 

 directly on the muscles but indirectly upon the cranio-spinal ganglia. 

 A volition is a conscious conception, a desire ; an act is the result of 

 the automatic unconscious origination and co-ordination, by the 

 cranio-spinal ganglia, of the nervous influences required to produce 

 certain muscular contractions. 



Whatever may be the ultimate cause of our actions then, the 

 proximate cause lies in nerve substance. The nervous system is a 

 great piece of mechanism placed between the external world and our 

 consciousness ; through it objects affect us ; through it we affect 

 them ; and it therefore becomes a matter of the highest interest to 

 ascertain how far the properties and laws of action of nerve substance 

 have been ascertained by the physiological philosopher. 



Nerve substance has long been known to consist of two elements, 

 fibres and ganglionic corpuscles. Nerve fibres are either sensory or 

 motor, and the activity of any one fibre does not influence another. 

 But when nerve fibres come into relation with ganglionic corpuscles, 

 the excitement of a sensory nerve gives rise to that of a motor nerve, 

 the ganglionic corpuscles acting in some way as the medium of com- 

 munication. The "grey matter" which occupies the middle of the 

 spinal marrow has long been known to be the locality in which the 

 posterior roots, or sensory fibres, of the nerves of the body, and the 

 anterior roots, or motor fibres, come into relation with ganglionic 

 corpuscles ; and as the channel by which, in what are called reflex 

 actions, the activity of the sensory nerves is converted into excitement 

 of corresponding motor nerves. The precise modus operandi of the 



