1857.] as to the Structure and Functions of Nerve, 435 



is perfectly clear that consciousness and volition are entirely 

 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. 



Now, (still carefully excluding the phenomena of conscious- 

 ness,) 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. Thb 

 cranio-spinal nervous centre originates and co-ordinates the con- 

 tractions of all the muscles of the body independently of conscious- 

 ness, and there is every reason to believe that the organ of con- 

 sciousness 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 con- 

 scious 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 mus- 

 cular 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 ele- 

 ments, 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 communication. 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 con- 

 verted into excitement of corresponding motor nerves. The precise 

 modus operandi of the grey matter has been much disputed, but 

 the recent researches of Wagner, Bidder, Kupfer, and Owsjannikow, 

 throw a great light upon, and \astly simplify the whole problem. 

 It would appear that all nerve fibres are processes of ganglionic 



2h2 



