THE CERVICAL SYMPATHETIC TRUNK 349 
nerve impulses through the ganglion, we have shown to be formed 
by the branching of the preganglionic fibers. In a paper which 
follows, Johnson presents conclusive evidence that commissural 
neurones do not exist in the ganglia of the sympathetic trunk of 
the frog. 
Finally, diffusion of nerve impulses might occur through 
collaterals given off by the postganglionic axons before they left 
the ganglion. 
That such collaterals exist has been shown by Dogiel, but we 
must conclude from his descriptions and figures that they do not 
occur on the majority of the axons. Michailow does not find 
them except on the axons of his cells of Type [X. He shows that 
they end in plates located in the connective tissue of the gangha 
between the nerve cells or against the outside of the capsule of a 
nerve cell. This mode of termination does not speak for them as 
serving the function of transferring impulses from one neurone to 
another. In fact, they rather resemble certain collaterals from 
the axons of spinal ganglion cells which in all probability serve 
no such function. 
The complete absence of fine branching axons in the superior 
cervical ganglion after degeneration of the preganglionic fibers 
is strong evidence against the existence of connections between 
the various cells of the ganglia. In such a ganglion the post- 
ganglionic axons can be seen to accumulate in bundles of parallel 
fibers and run as directly as possible toward the emerging nerves. 
From all that has been said we may conclude that there is no 
physiological or histological evidence for the existence in the 
superior cervical ganglion of a mechanism for the general diffu- 
sion of nerve impulses. And the same conclusion would prob- 
ably be equally valid for all the ganglia of the sympathetic 
trunk. We have already discussed the question of commissural 
fibers joining cells located in adjacent ganglia. 
Are there any synapses between sensory and motor neurones 
within the superior cervical ganglion such as would be required 
by the conception of the ganglion as a center for visceral reflexes? 
So far as we have been able to learn, no one has ever described 
any reflex through this ganglion. According to Langley (’00 a), 
