EXAMPLES OP THE FOUR METHODS. 467 



of the Method of Difference, requiring no comment. A further 

 and very important corroboration was obtained by the same 

 method. When the animal was killed, not shortly after the 

 section of the nerve, but a month later, the effect was reversed ; 

 rigidity set in sooner, and lasted a shorter time, than in the 

 healthy muscles. But after this lapse of time, the paralysed 

 muscles, having been kept by the paralysis in a state of rest, 

 had lost a great part of their irritability, and instead of more, 

 had become less irritable than those on the healthy side. This 

 gives the A B C, a b c, and B C, b c, of the Method of Dif- 

 ference. One antecedent, increased irritability, being changed, 

 and the other circumstances being the same, the consequence 

 did not follow ; and moreover, when a new antecedent, con- 

 trary to the first, was supplied, it was followed by a contrary 

 consequent This instance is attended with the special advan- 

 tage, of proving that the retardation and prolongation of the 

 rigidity do not depend directly on the paralysis, since that was 

 the same in both the instances ; but specifically on one effect 

 of the paralysis, namely, the increased irritability ; since they 

 ceased when it ceased, and were reversed when it was reversed. 



2ndly. Diminution of the temperature of muscles before 

 death increases their irritability. But diminution of their tem- 

 perature also retards cadaveric rigidity and putrefaction. 



Both these truths were first made known by Dr. Brown- 

 Sequard himself, through experiments which conclude accord- 

 ing to the Method of Difference. There is nothing in the 

 nature of the process requiring specific analysis. 



Srdly. Muscular exercise, prolonged to exhaustion, dimi- 

 nishes the muscular irritability. This is a well-known truth, 

 dependent on the most general laws of muscular action, and 

 proved by experiments under the Method of Difference, con- 

 stantly repeated. Now it has been shown by observation that 

 overdriven cattle, if killed before recovery from their fatigue, 

 become rigid and putrefy in a surprisingly short time. A 

 similar fact has been observed in the case of animals hunted to 

 death ; cocks killed during or shortly after a fight ; and 

 soldiers slain in the field of battle. These various cases agree 



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