474 



COMPARATIVE PHYSIOLOGY. 



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- 



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LOWER LIMIT OF 

 MEDULLA 



Fig. 338.— Diagram showing course of fibers in spinal cord (after Eanney). 1, 1', direct 



Syramidal bundles; 2, 2', crossed pyramidal Dundles, decussating in medulla; 3. 3', 

 irect cerebellar fibers; 4,4', fibers related to "muscular sense," decussatmg in 

 medulla ; 5, 5', and 6, 6', fibers relating to the appreciation of touch, pain, and 

 temperature. The motor bundles have a dot upon them to represent the motor 

 cells of the cord (anterior horn). Note that the motor fibers escape from the ante- 

 rior nerve-root (a. r.), and that the sensory bundles enter at the posterior nerve- 

 root (p. r.), which has a ganglion (g) upon it. 



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. 



It would seem that the lateral columns are the great high- 



