SPINAL CORD. Ill 



and the loss of sensibility will be complete. At the same time, 

 on the same side as the section the sensory function may be ex- 

 aggerated, and there may be hypersesthesia to such a degree that 

 even a touch may cause exquisite pain. 



What results follow electrical stimulation of the posterior columns 



of the cord ? 



If stimuli be applied to the posterior columns of the cord by 

 a galvanic current, signs of sensibility are shown in the reflex 

 actions ; but it is only near the nerve-roots that the sensibility 

 seems very marked. The intensity of the response increases with 

 the strength of the current. 



What reaction follows a similar stimulation of the anterior col- 

 umns. 



Motion in the parts below, and the motion is of a convulsive 

 character. No pain seems to accompany the convulsive contrac- 

 tions of the muscles. 



What is the effect in the lateral columns? 



The stimulation of the anterior portion results in motion, which 

 gradually decreases as one approaches the posterior nerve-roots, 

 and then merges into the signs of sensibility similar to those 

 excited by stimuli applied to the posterior columns. 



What practical lesson does this impress? 



That inflammatory changes in the meninges of the posterior 

 portion of the cord excite pain, while meningitis of the anterior 

 portion excites convulsions. 



What important function, besides conduction, does the spinal cord 

 perform ? 



The origination of motion in response to stimuli, or reflex action. 



What difficulties present themselves in the study of the reflex 



function of the cord in mammals ? 



The great shock which follows injury of the spinal cord in mam- 

 mals renders the study of its function difficult. It is sometimes 

 hours, or even days, before any experiments can be conducted after 

 the division of the cord in a warm-blooded animal, because of the 

 failure of the reflexes to act ; and when they do act the amount of 

 degeneration which has followed the operation is uncertain. Cold- 

 blooded animals (especially the frog) are used largely in such 



