MancJiester Memoirs, Vol. xlii. (1898), No. \%. 5 



difficulty of distinguishing between actual fusion and mere 

 contact being in many situations exceedingly great, and 

 the instances where the linkage is obviously one of contact 

 only being exceedingly numerous. And, indeed, while 

 admitting that the existence of a distinct mechanical gap 

 is not an essential feature of the linkage, we may still 

 assume that at each linkage there is between the linked 

 units a line of demarcation, the material on the one side 

 of which differs from that on the other. 



Passing now to the question, what are the physical 

 events, the events which we can lay hold of objectively, 

 which take place during the life of a nerve cell, and 

 which we may assume to be different when the nerve 

 cell is at rest from what they are when the nerve cell 

 is in a state of activity, we find that nearly all our 

 exact knowledge is derived from observations made 

 on nerve cells or parts of nerve cells prolonged outside the 

 central nervous system as nerve fibres connecting that 

 central nervous system, the brain or the spinal cord, with the 

 various tissues of the body. These nerve fibres are on the 

 one hand efferent fibres, the channels or instruments by 

 which the central nervous system transmits influences to, 

 or acts upon muscular and other tissues; and, on the other 

 hand, afferent fibres, the channels or instruments by which 

 various tissues, as the result of changes taking place in 

 them, transmit influences to, or produce effects in the 

 central nervous system. 



The efferent nerve fibre is simply the prolonged axon 

 of a nerve cell lying in the spinal cord or brain; the axon, 

 for instance, of a cell whose nucleus and dendrites lie 

 wholly within the spinal cord, leaves the spinal cord, and 

 pursues its way, clothed with myelin or medulla and sup- 

 ported by connective tissue, until it reaches its destination, 

 a muscular fibre for example, in which, after previous 

 division, it ends in a terminal arborescence in connection 



