186 
Proceedings of Royal Society of Edinburgh. 
SESS. 
by the dendritic processes always towards the ceil, and by the axis- 
cylinder and its terminal arborizations always from the cell. In m;y 
opinion, the first statement at present rests on insufficient proof, 
and it will be noticed that, if we admit the second, it upsets the 
older notion of a sensory impulse travelling along a sensory nerve 
from the skin ultimately reaching a nerve cell, say in the cord or 
brain. Further, this statement carries with it a number of start- 
ling conclusions. For example, if the dendritic processes always 
carry impulses towards the cell, the numerous fine axis-cylinders in 
an area of skin, which supply sensibility to that part, must be re- 
garded as the dendritic processes of a bipolar cell in a ganglion on 
the posterior root of a spinal nerve, and the sensory filament we 
have hitherto regarded as an axis-cylinder as a specially enlarged 
division of the dendritic arrangement. If this be so, then the axis- 
cylinder beyond the ganglion is the true axis-cylinder, and its 
arborization in the cord, by which it may become related to another 
neuron, is the liomologue of the end plates at the termination of a 
motor axis-cylinder. Again, if we trace sensory fibres up the cord 
and onwards to the cerebral cortex, these fibres are true axis- 
cylinders, and they end in fine fibrils (again homologous with the 
end plates in muscle), by which an arborization is formed, bringing 
them into relation with the dendritic processes of a neuron, the 
body of which is in the grey matter of the cortex, and which is 
presumably motor. 
There is also a difficulty in understanding the true significance 
of the fine fibrils, already alluded to, which pass off at right angles 
from the main stems. If these come off from fibrils that are con- 
tinuations of the dendron, as they do in the grey layers of the 
cerebrum, do they conduct nervous impulses downwards and out- 
wards to the dendrons of adjacent cells, or do they carry impulses 
from such cells to the cell from the dendron of which they spring ? 
and if they come off from the true axis-cylinder process, do they 
conduct outwards, so as to bring their parent cell into connection, 
by terminal arborizations, with other structures ? 
Again, if there is no continuity of structure, and only contiguity 
of terminations , how is a nervous impulse transmitted from one 
neuron to another ? Some have suggested that this may occur by 
actual movements of the terminations, in a manner analogous to 
