304 INDUCTION. 



" a violent convulsion of every muscle in the body," of which, if of suffi- 

 cient intensity, the knovtai effect would be that "muscular irritability 

 ceases almost at once." If Dr. Brown-Sequard's generalization is a true 

 law, these will be the very cases in which rigidity is so much abridged as 

 to escape notice ; and the cases in which, on the contrary, rigidity takes 

 place as usual, will be those in which the stroke of lightning operates in 

 some of the other modes which have been enumerated. How, then, is this 

 brought to the test? By experiments, not on lightning, which can not be 

 commanded at pleasure, but on the same natural agency in a manageable 

 form, that of artificial galvanism. Dr. Brown-Sequard galvanized the en- 

 tire bodies of animals immediately after death. Galvanism can not operate 

 in any of the modes in which the stroke of lightning may have operated, 

 except the single one of producing muscular convulsions. If, therefore, af- 

 ter the bodies have been galvanized, the duration of rigidity is much short- 

 ened and putrefaction much accelerated, it is reasonable to ascribe the 

 same effects when produced by lightning to the property which galvanism 

 shares with lightning, and not to those which it does not. Now this Dr. 

 Brown-Sequard found to be the fact. The galvanic experiment was tried 

 with charges of very various degrees of strength ; and the more powerful the 

 charge, the shorter was found to be the duration of rigidity, and the more 

 speedy and rapid the putrefaction. In the experiment in which the charge 

 was strongest, and the muscular irritability most promptly destroyed, the 

 rigidity only lasted fifteen minutes. On the principle, therefore, of the 

 Method of Concomitant Variations, it may be inferred that the duration 

 of the rigidity depends on the degree of the irritability; and that if the 

 charge had been as much stronger than Dr. Brown-Sequard's strongest, as 

 a stroke of lightning must be stronger than any electric shock which we 

 can produce artificially, the rigidity would have been shortened in a corre- 

 sponding ratio, and might have disappeared altogether. This conclusion 

 having been arrived at, the case of an electric shock, whether natural or 

 artificial, becomes an instance, in addition to all those already ascertained, 

 of correspondence between the irritabiUty of the muscle and the duration 

 of rigidity. 



All these instances are summed up in the following statement: "That 

 when the degree of muscular irritability at the time of death is considera- 

 ble, either in consequence of a good state of nutrition, as in persons who 

 die in full health from an accidental cause, or in consequence of rest, as in 

 cases of paralysis, or on account of the influence of cold, cadaveric rigidity 

 in all these cases sets in late and lasts long, and putrefaction appears late, 

 and progresses slowly ;" but " that when the degree of muscular irritability 

 at the time of death is slight, either in consequence of a bad state of nu- 

 trition, or of exhaustion from overexertion, or from convulsions caused by 

 disease or poison, cadaveric rigidity sets in and ceases soon, and putrefac- 

 tion appears and progresses quickly." These facts present, in all their 

 completeness, the conditions of the Joint Method of Agreement and Dif- 

 ference. Early and brief rigidity takes place in cases which agree only in 

 the circumstance of a low state of muscular irritability. Rigidity begins 

 late and lasts long in cases which agree only in the contrary circumstance, 

 of a muscular irritability high and unusually prolonged. It follows that 

 there is a connection through causation between the degree of muscular ir- 

 ritability after death, and the tardiness and prolongation of the cadaveric 

 rigidity. 



This investigation places in a strong light the value and efficacy of the 



