406 S. W. RANSON AND P. R. BILLINGSLEY 
About half of the material was fixed in osmic acid and the 
remainder in ammoniated absolute alcohol for the pyridine 
silver stain. The rami communicantes are so small and short 
that pyridine silver preparations were made in only a few in- 
stances, so that our observations on these are based chiefly on - 
osmic acid preparations. For the rest of the work abundant 
material was available in which to compare the myelin sheath 
and axon content of the various parts of the sympathetic trunk 
and the splanchnic nerve. 
When small nerves are subjected to the action of the silver 
and pyrogallic acid a diffuse precipitate forms throughout the 
specimen which renders it useless for microscopic study. In 
order to do away with this it is only necessary to subject large 
blocks of tissue to the action of the reagents. This can best be 
accomplished by imbedding the nerve in the spinal cord. The - 
small nerve to be studied is dissected free and a fine silk thread is 
tied at either end of the stretch to be removed. With the aid of 
a long straight slender needle the thread attached to the end of 
the nerve is drawn through a piece of spinal cord and the nerve 
drawn in after it. The spinal cord should be prepared before 
the nerve is dissected out. The cervical portion of the cat’s cord 
freed from dura and split in the median sagittal plane into two 
lateral halves makes satisfactory blocks. Each lateral half is 
then cut into segments a little longer than the pieces of nerve 
to be removed. During these manipulations the nerve and 
cord should be protected from drying by the use of normal salt 
solution. In drawing the nerve into the cord the needle is run 
longitudinally through the anterior gray column and the thread 
pulled through until the nerve lies imbedded in the cord. The 
segment of the cord is then laid with its lateral convex surface 
upon a glass cover-slip and the silk threads attached to either 
end of the nerve are tied over the cover-slip so as to put gentle 
traction on the nerve. After two hours in ammoniated alcohol 
the silk thread can be cut off near the cord, which is then removed 
from the cover-slip and pared down with a razor until it forms a 
bar, the cross-section of which is not more than 4 mm. square. 
This should consist chiefly of the anterior gray column in which 
the nerve lies imbedded. 
