EXAMPLES OF THE FOUR METHODS. 465 



The accumulated proof of which the Theory of Dew has 

 been found susceptible, is a striking instance of the fulness of 

 assurance which the inductive evidence of laws of causation 

 may attain, in cases in which the invariable sequence is by no 

 means obvious to a superficial view. 



4. The admirable physiological investigations of Dr. 

 Brown-Sequard afford brilliant examples of the application 

 of the Inductive Methods to a class of inquiries in which, for 

 reasons which will presently be given, direct induction takes 

 place under peculiar difficulties and disadvantages. As one of 

 the most apt instances I select his speculation (in the Pro- 

 ceedings of the Royal Society for May 16, 1861) on the rela- 

 tions between muscular irritability, cadaveric rigidity, and 

 putrefaction. 



The law which Dr. Brown-Sequard's investigation tends 

 to establish, is the following : " The greater the degree of 

 muscular irritability at the time of death, the later the cada- 

 veric rigidity sets in, and the longer it lasts, and the later also 

 putrefaction appears, and the slower it progresses." One 

 would say at first sight that the method here required must 

 be that of Concomitant Variations. But this is a delusive ap- 

 pearance, arising from the circumstance that the conclusion to 

 be tested is itself a fact of concomitant variation. For the 

 establishment of that fact any of the Methods may be put in 

 requisition, and it will be found that the fourth Method, though 

 really employed, has only a subordinate place in this particular 

 investigation. 



The evidences by which Dr. Brown-Sequard establishes the 

 law may be enumerated as follows : 



1st. Paralysed muscles have greater irritability than 

 healthy muscles. Now, paralysed muscles are later in as- 

 suming the cadaveric rigidity than healthy muscles, the rigidity 



any thermoraetric effect at the earth's surface. Even, therefore, in a case so 

 favourable as this to Nature's experimental talents, her experiment is of little 

 value except in corroboration of a conclusion already attained through other 

 means. 



VOL. I. 30 



