278 



INDUCTION. 



Method of DiflFerence. Now, in the 

 case of those who died from accident 

 or violence, with their muscles in a 

 good state of nutrition, the muscular 

 irritability continues long after death, 

 rigidity sets in late, and persists long 

 without the putrefactive change. On 

 the contrary, in cases of disease in 

 which nutrition has been diminished 

 for a long time before death, all these 

 effects are reversed. These are the 

 conditions of the Joint Method of 

 Agreement and Difference. The cases 

 of retarded and long-continued rigi- 

 dity here in question agree only in 

 being preceded by a high state of 

 nutrition of the muscles ; the cases 

 of rapid and brief rigidity agree only 

 in being preceded by a low state of 

 muscular nutrition ; a connection is 

 therefore inductively proved between 

 the degree of the nutrition and the 

 slowness and prolongation of the rigi- 

 dity. 



5thly. Convulsions, like exhausting 

 exercise, but in a still greater degree, 

 diminish the muscular irritability. 

 Now, when death follows violent and 

 prolonged convulsions, as in tetanus, 

 hydrophobia, some cases of cholera, 

 and certain poisons, rigidity sets in 

 Tery rapidly, and, after a very brief 

 duration, gives place to putrefaction. 

 This is another example of the Method 

 of Agreement, of the same character 

 with No. 3. 



6thly. The series of instances which 

 we shall take last is of a more com- 

 plex character, and requires a more 

 minute analysis. 



It has long been observed that in 

 some cases of death by lightning cada- 

 veric rigidity either does not take place 

 at all, or is of such extremely brief 

 duration as to escape notice, and that 

 in these cases putrefaction is very ra- 

 pid. In other cases, however, the usual 

 cadaveric rigidity appears. There 

 must be some difference in the cause 

 to account for this difference in the 

 •ffect Now "death by lightning 

 may be the result of, let, a syncope 

 by fright, or in consequence of a direct 

 or reflex influence of lightning on the 



par vagum ; 2dly, hemorrhage in or 

 around the brain, or in the lungs, the 

 pericardium, &c. ; 3dly, concussion, 

 or some other alteration in the brain ;" 

 none of which phenomena have any 

 known property capable of account- 

 ing for the suppression, or almost 

 suppression, of the cadaveric rigidity. 

 But the cause of death may also be 

 that the lightning produces " a violent 

 convulsion of every muscle in the 

 body," of which, if of sufficient in- 

 tensity, the known effect would be 

 that " muscular irritability ceases 

 almost at once." If Dr. Brown- 

 S^quard's generalisation 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 cannot be 

 commanded at pleasure, but on the 

 same natural agency in a manageable 

 form, that of artificial galvanism. Dr. 

 Brown-S^quard galvanised the entire 

 bodies of animals immediately after 

 death. Galvanism cannot operate in 

 any of the modes in which the stroke 

 of lightning may have operated, ex- 

 cept the singular one of producing 

 muscular convulsions. If, therefore, 

 after the bodies have been galvanised, 

 the durati jn of rigidity is much short- 

 ened and putrefaction much accele- 

 rated, it is reasonable to ascribe the 

 same effects when produced by light- 

 ning to the property which galvanism 

 shares with lightning, and not to 

 those which it does not. Now this 

 Dr. Brown -S^quard 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 



