730 REPORT—1904. 
discovery gave them meaning, but before the vasomotor mechanism was discovered. 
The blood-vessels of an organ may be turgid at one time, constricted almost to 
obliteration at another. With the conductive network of the nervous system the 
temporal changes are even greater, for they extend to absolute withdrawal of 
nervous influence. Our schemata of the pattern of the great central organ take no 
account of temporal data. But the pattern of the web of conductors is not 
really immutable. Functionally its details change from moment to moment. In 
any active part it is a web that shifts from one pattern to another, from a first to 
a second, from a second to a third, then back perhaps to the first, and then to a 
fourth, and so on backwards and forwards. As a tap to a kaleidoscope, so a new 
stimulus that strikes the central organ causes it to assume a partially new pattern. 
The pattern in general remains, but locally the patterns are in constant flux 
of back and forward change. These time-changes offer, I venture to think, a 
study important for understanding the integrative function of the nervous system. 
If we regard the nervous system of any higher organism from the broad point 
of view, a salient feature in its architecture is the following. At the commence- 
ment of every reflex arc is a receptive neurone, extending from the receptive 
surface to the central nervous organ, That neurone forms the sole avenue which 
impulses generated at its receptive point can use whithersoever may be their 
distant destination. That neurone is therefore a path exclusive to the impulses 
generated at its own receptive points, and other receptive points than its own 
cannot employ it. 
But at the termination of every reflex are we find a final neurone, the 
ultimate conductive link to an effector organ, gland or muscle. This last link in 
the chain, eg., the motor neurone, differs obviously in one important respect 
from the first link of the chain. It does not subserve exclusively impulses 
generated at one single receptive source alone, but receives impulses from many 
receptive sources situate in many and various regions of the body. It is the sole 
path which all impulses, no matter whence they come, must travel if they would 
reach the muscle-fibres which it joins. Therefore, while the receptive neurone 
forms a private path exclusive for impulses of one source only, the final or efferent 
neurone is, so to say, a public path, common to impulses arising at any of many 
sources in a variety of receptive regions of the body: The same effector organ 
stands in reflex connection not. only with many individual receptive points, 
but even with many various receptive fields. Reflex arcs arising in manifold 
sense-organs can pour their influence into one and the same muscle. A limb- 
muscle is the terménus ad quem of nervous arcs arising not only in the right eye 
but in the left, not only in the eyes but in the organs of smell and hearing; not 
only in these, but in the geotropic labyrinth, in the skin, and in the muscles and 
joints of the limb itself and of the other limbs as well, Its motor nerve is a 
path common to all these. 
Reflex arcs show therefore the general feature that the initial neurone is a 
private path exclusive for a single receptive point; and that finally the arcs 
embouch into a path leading to an effector organ, and that this final path is 
common to all receptive points wheresoever they may lie in the body, so long as 
they have any connection at all with the effector organ in question. Before finally 
converging upon the motor neurone arcs usually converge to some degree by their 
private paths embouching upon internuncial paths common in various degree to 
groups of private paths. The terminal path may, to distinguish it from inter- 
nuncial common paths, be called the final common path. The motor nerye to a 
muscle is a collection of such final common paths. 
Certain results flow from this arrangement. One seems the preclusion of 
qualitative differences between nerve-impulses arising in different afferent nerves. 
If two conductors haye a tract in common, there can hardly be qualitative 
difference between their modes of conduction. 
A second result is that each receptor being dependent for communication with 
its effector organ upon a path not exclusively its own but common to it with 
certain other receptors, that nexus necessitates successive and not simultaneous 
use of the common path by various receptors using it to different effect, 
