466 



COMPARATIVE PHYSIOLOGY. 



Pig. 339.— Multipolar ganglion cell from anterior 

 gray matter of spinal cord of ox (after Dei- 

 fers). a, axis cylinder process; A, branched 

 processes. 



Now, in reality this is 

 very complex, though it 

 can be analyzed into ite 

 factors. Thus, afferent 

 nerves are concerned, the 

 spinal cord as a reflex 

 center, efferent nerves to 

 the muscles called into 

 action, the cord as a con- 

 ductor of impulses which 

 result in sensations, emo- 

 tions, and thoughts refer- 

 able to the brain ; so that 

 if we would grasp the state 

 of affairs it is of impor- 

 tance to so combine the 

 various processes in our 

 merrtal conception that it 

 shall in our miads form 

 that whole which corre- 

 sponds with nature, as we 

 have been insisting upon 

 in the last chapter. With 

 this admonition, and as- 

 suming a good kaowledge 

 of the general and minute 

 anatomy of the spinal 

 cord, we shall proceed to 

 discuss its functions. 



THE REFLEX FUNCTIONS. OF THE SPINAL CORD. 



The following experimental observations may readily be 

 made by the student himself: Let a decapitated frog be sus- 

 pended freely (from the lower jaw). It hangs motionless and 

 limp at first, but when it recovers from the shock (abolition of 

 function) to the spinal cord produced by the operation, it may 

 be shown that this organ is functional : 1. When a piece of 

 bibulous paper dipped in dilute acid is placed upon the thigh, 

 the leg is drawn up and wipes away the offending body. 3. If 

 the paper be placed on the anus, both legs may be drawn up, 

 either successively or simultaneously. 3. If the leg of one 



