492 ANIMAL PHYSIOLOGY. 
rior columns. From the cells of the anterior cornua, impulses 
travel by the anterior nerve-roots to the motor nerves, by 
which connection is made with the muscles. 2. Sensory im- 
pulses enter the cord from the afferent nerve-fibers by the pos- 
terior nerve-roots, passing probably by the posterior columns to 
the posterior cornua, thence to the lateral columns, decussation 
being largely immediate though not completed for some dis- 
tance up the cord. 
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Fic. 849._Diagram showing course of fibers in spinal cord (after Ranney). 1, 1’, direct pyrami- 
dal bundles; 2, 2’, crossed pyramidal bundles, decussating in medulla; 38, 3’, direct 
cerebellar fibers ; 4, 4’, fibers related to “‘ muscular sense,” decussating in medulla; 5, &’, 
and 6, 6’, fibers related to the appreciation of touch, pain, and temperature. The motor 
bundles have a dot pen them to represent the motor cells of the cord (anterior horn). 
Note that the motor fibers escape from the anterior nerve-root (a. r.), and that the sensory 
bundles enter at the posterior nerve-root (p. 7.), which has a ganglion (g) upon it. 
It would seem that the lateral columns are the great high- 
ways of impulses; though in all instances it is likely that the 
gray matter of the cord plays an important part in modify- 
ing them before they reach their destination. Some observers 
