316 S. W. RANSON AND P. R. BILLINGSLEY 
that any advantage was obtained by this procedure. It is true 
that the majority of our best preparations of the preganglionic 
fibers were obtained in this way, but since we occasionally ob- 
tained just as good stains in normal animals we are in doubt 
as to the value of the preliminary division of the fibers. We 
shall consider these as preparations of the normal ganglia since 
if there is any change it is only in the direction of an increased 
affinity of these fibers for the silver. 
In order to obtain complete degeneration of the preganglionic 
fibers the sympathetic trunk was divided in the neck. The 
operation was performed aseptically on cats and dogs, the nerve 
being cut about 2 inches below the ganglion. After periods of 
from eight to fifty days some of the animals were killed. It was 
found that after the longer periods some regeneration had oc- 
curred and the shorter periods were scarcely adequate for full 
degeneration. In order to avoid these difficulties, a second 
operation was performed on some of the animals twenty to 
fifty days after the first, the nerve being cut cephalad to the 
neuroma. Eight days after the second operation the animals 
were killed. 
In dealing with small nerves and ganglia we have found that 
the pyridine silver stain often fails to give good results apparently 
because the volume of the tissue is too small. In order to over- 
ecme this difficulty we find it desirable to imbed the small nerve 
or ganglion in the spinal cord. For this purpose we have tied a 
fine silk thread to the sympathetic trunk and with a long fine 
needle have drawn the trunk with the attached superior cervical 
ganglion and internal carotid nerve into a lateral half of the 
spinal cord along the line of the ventral gray column. After 
fixation for two hours in ammoniated alcohol the block of spinal 
cord can be pared down with a razor until it forms a bar the cross- 
section of which is not more than 4 mm. square. Within this 
block of cord the nerve is held extended and straight and is pro- 
tected from the two direct action of the reagents. The cord is 
dissected away from the nerve just before it is dehydrated and 
cleared in preparation for imbedding. 
