1887.J 



and its Relation to Putrefaction. 



449 



there does not seem to be usually an intimate relation between the 

 apparent intensity and the duration, for a short-lived rigor produced 

 .at a high temperature may look most pronounced, while a fish 

 in a strong rigor (which may last for twenty-four hours or more) 

 has often neither the gill-covers nor fins extended, nor the body dis- 

 tinctly arched. We must suppose that there is some relation between 

 the duration of the rigor and the condition of the muscles when it 

 sets in. If before the rigor appears the latent energy of the muscles 

 has been all but exhausted, either before or after death, naturally or 

 artificially, the rigor though well marked will be of short duration, 

 while on the other hand if a considerable amount of rigor-producing 

 material is left when the stiffening supervenes, the rigor, though not 

 strikingly resembling a tetanic spasm, will be more intense and more 

 persistent. 



As the rigor comes on, all the muscles shorten (or contract), the 

 extensors usually overcoming the flexors and the muscles of one side 

 (or probably the red muscles of one side) overcoming the muscles of 

 the other, and thus leading to arching or lateral curvature of the 

 trunk. This curving is sometimes so intense that a fish 10 inches in 

 length may form the arc of a circle little over 6 inches in diameter. 

 Up to a certain time after the rigor sets in it may, either by electrical 

 stimulation or mechanically, be broken down, not once, but several 

 times ; but the oftener the coming on of the rigor is interfered with, 

 the final rigor is the weaker and the less persistent. Apparently at 

 ordinary temperatures there is a regular order, not only in the stiffen- 

 ing of the various groups of muscles, but also of the various bundles 

 of the individual muscles. If this is the case, the alternate appear- 

 ance and disappearance of the rigor may, as already indicated, be 

 accounted for by saying that when a partial rigor is broken down, the 

 stiffening of certain muscles or portions of muscles has been arrested 

 or destroyed, and when the rigor sets in again new muscles or muscular 

 bundles have stiffened, while those in which the rigor had previously 

 appeared either remain limp or have their rigidity completed. When 

 rigor which has been fully established in isolated muscles or groups 

 of muscles is destroyed, it never reappears. I have not yet succeeded 

 in recording in a satisfactory manner the strength of the rigor under 

 different conditions, but from the results already obtained, it appears 

 the more rapidly the rigor comes on the more closely it resembles an 

 ordinary muscle contraction. 



A comparative table showing the changes which take place in the 

 muscles of different animals at different temperatures while the rigor 

 is coming on and going off would be very instructive. It may be 

 mentioned that in fish, as in other vertebrates, as the rigor comes on 

 there is a rise in temperature, and the reaction changes often 

 rapidly from slightly alkaline or neutral to distinctly acid. In a 



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