72 ON THE NATURE AND ACTION OF THE 



Action on the Spinal Cord. 



The spinal cord has the threefold function of a conductor of 

 sensory impressions, a conductor of motor impressions, and a 

 reflex centre ; and in examining into the nature of the action 

 of cobra-poison upon it, we must consider the manner in which 

 each of these functions is affected. 



Cobra-poison, as has already been intimated, has a powerful 

 paralysing action upon the reflex function of the cord ; and this 

 is exemplified in Experiment XLVII, etc. 



As a conductor of sensory impressions, the cord is able to 

 transmit two kinds, viz., tactile and painful, and these have been 

 stated to pass through different parts of the cord, the former 

 being conveyed by the posterior and lateral white columns, and 

 the latter by the grey matter. 



From Experiments XXXVI and LX it would appear that 

 the power to convey tactile impressions is retained, both in 

 warm-blooded animals and frogs, after the transmission of 

 painful impressions has almost, or entirely, ceased. Thus, in 

 Experiment XXXVI the frog's leg moved when the animal was 

 laid upon its back, although an extremely painful stimulus, the 

 application of sparks from a coil to the eye, had caused in it 

 only the feeblest movement. In Experiment LX no response 

 was elicited by striking, pinching, or pricking the paws of the 

 animal, but when the ear was tickled the cat shook its head, or 

 moved its paw to ward off the irritant. 



Erom these cases we think we are justified in concluding that 

 the grey matter of the spinal cord, thiough which painful 

 impressions are transmitted, is paralysed by cobra-poison ; but 

 the white sensory columns are little, if at all, affected. The 

 power of the cord to conduct motor impressions from the 

 encephalic ganglia appears to be little, if at all, affected, until 

 the apparent death of the animal; for in Experiment LX we 

 find that, very shortly before respiration ceased, and when 

 ordinary reflex action from the cord was nearly gone, purposive 

 or voluntary movements were still made. The absence of 

 movements in Experiment L, when the cord was irritated by a 

 needle, as well as the rapid loss of its power to produce move- 

 ment in the limbs when irritated by a Earadic current, is, we 



