THE CERVICAL SYMPATHETIC TRUNK 315 
and follow along its branches to the glands. Through the supe- 
rior cardiac nerve postganglionic fibers run to the heart in man. 
Other postganglionic fibers join the upper four spinal nerves and 
the ninth, tenth, and twelfth cranial nerves to be distributed to 
the blood-vessels and glands in the regions supplied by these 
nerves, and still others run by the laryngopharyngeal - branches 
of the superior cervical ganglion to the larynx and pharynx. 
This will serve as a general survey of the field to be studied. 
In the pages which follow we will take up in detail the structure 
of the superior cervical ganglion, sympathetic trunk and internal 
carotid nerve and pay particular attention to the synapses which 
occur in the ganglion. 
MATERIAL AND METHODS 
The superior cervical ganglion of man, the dog, and cat were 
prepared by the pyridine silver method and cut into sections 
12 to 20 micra thick. Osmie acid preparations were also made 
from the dog and cat. Many of the preparations were cut into 
serial sections at right angles to the long axis of the ganglion, 
beginning at the internal carotid nerve and extending through 
the ganglion and some distance along the sympathetic trunk. 
Other ganglia were also examined, such as the stellate ganglion 
of the cat and the superior cervical ganglion in the rabbit. 
In addition to the study of these parts in normal animals, 
experiments were carried out to determine the effect of partial 
and of complete degeneration of the preganglionic fibers. It 
had been noticed in a study of degenerating and regenerating 
nerves, made several years previously that certain fibers in the 
early stages of degeneration showed an increased affinity for sil- 
ver. It was hoped that this might furnish a clue which would 
lead to the development of a differential stain for degenerating 
axons. A number of ganglia were prepared by the pyridine 
silver method sixteen or seventeen hours after section of the 
sympathetic trunk in the neck to see if by this method the pre- 
ganglionic fibers might be made to stain more intensely through 
an increased affinity for the silver. So far we are not convinced 
