314 INNEBVATION. [CHAP. XI. 



pain and distress. Thus, parts which in their quiescent state are 

 insensible, become painful in the state of excitement. The cause of 

 this is no doubt to be found in a periodical exacerbation of the 

 primary disease of the cord, and the extension of the state of 

 excitement from the seat of the lesion to the whole cord ; to that 

 portion which is in connexion with the brain, as well as to that 

 which is below the lesion. 



The rigid and contracted state of the muscles of paralysed limbs, 

 which frequently accompanies red softening of the brain, arises 

 from the propagation of the excited state of the diseased part of the 

 brain to that portion of the spinal cord which is connected with it, 

 and from which the nerves of the paralysed parts arise. These 

 nerves likewise participate in the irritation of the cord, and thus 

 keep the muscles in a continual state of active contraction. There, 

 is no organic lesion of the cord in these cases ; its state of excite- 

 ment is dependent on the cerebral irritation. 



The convulsions of epilepsy arise from a similar cause, namely, 

 irritation of the brain, involving the whole or a part of the spinal 

 cord, and the nerves arising from it. In many instances the con- 

 vulsions are limited to one half of the body : in such cases there 

 is generally lesion of the brain on one side, and the cerebral excite- 

 ment is propagated only to one half (the opposite) of the cord. 



Some substances exert a peculiar influence upon the spinal 

 cord, and throw it into a state of considerable polar excitement. 

 Strychnine is the most energetic substance of this class. If a certain 

 quantity of this drug be injected into the blood, or taken into the 

 stomach of an animal, a state of general tetanus will quickly ensue, 

 sensibility remaining unimpaired. The slightest touch upon any 

 part of the surface, even a breath of wind blown upon it, will 

 cause a general or partial convulsive movement. The whole extent 

 of the cord is thrown into this polar state, and even the medulla 

 oblongata is involved in it; whence the closed jaws, the spasmodic 

 state of the facial muscles, the difficult deglutition. In this re- 

 markable state of excitement, it is curious to observe that the 

 spinal cord is perfectly natural in point of structure, as far as our 

 means of observation enable us to judge. We have examined some 

 spinal cords of animals which have died exhausted by the effects 

 of the strychnine, but have always found the nerve-tubes and other 

 elements of the cord exhibiting their natural appearance. 



Opium is capable of creating a similar state of polarity in the 

 cord. This is most conspicuous in cold-blooded animals ; but no 

 doubt it produces, in a much less degree, a similar effect in the 



