MUSCLES AND PHENOMENA OF CONTRACTION. 135 



tends to the lower extremities. After some time this rigor 

 begins to disappear and the dead body again becomes mov- 

 able at its joints. This loosening is usually attributed to 

 the beginning stage of decomposition, but this is probably 

 not right. According to the more general explanation rigor 

 mortis is due to the clotting of the muscle plasma. Such a 

 formation of a solid muscle clot would of course at once ex- 

 plain the immobility of the body. A more recent view, 

 however, and one which seems to have most in its favor, 

 explains rigor mortis as a final severe contraction of the 

 muscles brought about by the chemical changes which in- 

 duce death. It would be, in other words, a severe tetanus 

 produced by a series of disintegrating chemical changes 

 which accompany the dissolution of life. According to 

 this view the relaxation which follows after the rigor would 

 be merely a return of these muscles to their relaxed condi- 

 tion. That this rigor is probably a contraction and not a mere 

 coagulation of internal albumens is further supported by the 

 fact that a good deal of heat is liberated, and that the 

 muscles show all those phenomena which accompany ordi- 

 nary severe contraction. 



The Source of Muscular Energy. 



The view that muscles possessed a kind of vital energy, 

 which of course Could not therefore be measured like or- 

 dinary physical energies, has long been abandoned, and we 

 know now that muscles must derive their energy to contract 

 in accordance with the same laws that determine what the 

 energy - yielding power of an ordinary steam engine or 

 dynamo shall be. Muscle energy is identical per se with 

 physical and chemical energies. The question now arises, 

 in what manner, from the material that is carried to it by the 

 blood, does it get its energy to produce heat and motion? 

 Without going into a discussion of older views, the follow- 

 ing seems the explanation most in accord with all the ob- 

 served facts. 



