EXAMPLES OP THE FOUR METHODS. 



577 



of the Method of Difference were 

 adequately secured. 



In the same manner in which Dr. 

 Brown-S^quard proved that paralysed 

 muscles have greater irritability, he 

 also proved the correlative proposi- 

 tion respecting cadaveric rigidity and 

 putrefaction. Having, by section of 

 the roots of the sciatic nerve, and 

 again of a lateral half of the spinal 

 cord, produced paralysis in one hind- 

 leg of an animal while the other 

 remained healthy, he found that not 

 only did muscular irritability last 

 much longer in the paralysed limb, 

 but rigidity set in later, and ended 

 later, and putrefaction began later, 

 and was less rapid than on the healthy 

 side. This is a common case of the 

 Method of Difference, requiring no 

 comment. A further and very im- 

 portant 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 irri- 

 table than those on the healthy side. 

 This gives the A B C, a 6 c, and B 

 C, b c, of the Method of Difference. 

 One antecedent, increased irritability, 

 being changed, and the other circum- 

 stances being the same, the conse- 

 quence did not follow ; and, more- 

 over, when a new antecedent, contrary 

 to the first, was supplied, it was fol- 

 lowed by a contrary consequent. This 

 instance is attended with the special 

 advantage of proving that the retar- 

 dation and prolongation of the rigidity 

 do not depend directly on the paraly- 

 sis, since that was the same in both 

 the instances ; but specifically on one 

 •ffect of the paralysis, namely, the in- 

 creased irritability, since they ceased 

 when it ceased, and were reversed 

 when it was reversed. 



2dly. Diminution of the tempera- 



ture of muscles before death increases 

 their irritability. But diminution of 

 their temperature also retards cada- 

 veric rigidity and putrefaction. 



Both these truths were first made 

 known by Dr, Brown-S^quard him- 

 self, through expei'iments which con- 

 clude according to the Method of 

 Difference. There is nothing in the 

 nature of the process requiring specific 

 analysis. 



3dly. Muscular exercise, prolonged 

 to exhaustion, diminishes 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, constantly 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 in no circumstance 

 directly connected with the muscles, 

 except that these have just been sub- 

 jected to exhausting exercise. Under 

 the canon, therefore, of the Method 

 of Agreement, it may be inferred that 

 there is a connection between the two 

 facts. The Method of Agreement, 

 indeed, as has been shown, is not 

 competent to prove causation. The 

 present case, however, is already 

 known to be a case of causation, it 

 being certain that the state of the 

 body after death must somehow de- 

 pend upon its state at the time of 

 death. We are therefore warranted 

 in concluding that the single circum- 

 stance in which all the instances 

 agree is the part of the antecedent 

 which is the cause of that particular 

 consequent, 



4thly. In proportion at the nuti'i- 

 tion of muscles is in a good state, 

 their irritability is high. This fact 

 also rests on the general evidence of 

 the laws of physiology, grounded on 

 many familiar applications of the 



