590 MUSCLES. 



diminishes, water is given off, and a re-imbibition takes place and the 

 so-called " solution of the rigor " appears (v. FURTH and LENK). 



The ordinary rigor is an acid rigor and the same applies, according 

 to MEiGS, 1 to the water rigor as a shortening of the muscles takes place 

 when placed in distilled water, by a formation of lactic acid, and because 

 when such a muscle is placed in RINGER'S solution the acid is removed 

 and the muscle again expands. 



The views are rather contradictory in regard to the production of heat 

 rigor. According to v. FURTH this rigor depends upon the coagulation 

 of certain proteins, and its occurrence at lower temperatures in cold- 

 blooded as compared with warm-blooded animals is due, accojrding to 

 v. FURTH, to the fact that in the first a soluble myogen fibrin occurs 

 preformed in the muscle which coagulates at 30-40 C., while in the 

 warm-blooded animals the coagulating substance is musculin (myosin 

 of v. FURTH) which coagulates at a higher temperature. According 

 to INAGAKI 2 the various stages in contractions occurring on heating a 

 muscle (frog) do not correspond to those of the coagulation of the pro- 

 tein which would occur on heating the muscle plasma, and MEIGS has 

 arrived at a similar view. It must be remarked that also a lactic acid 

 formation takes place on heating a muscle, and this prevents an exact 

 comparison of the coagulation of the proteins within and outside 

 of the muscle. The observations of VERNON that the striated and 

 the smooth muscles on heating to between 40 and 50 behave differently, 

 in that the striated become shorter and the smooth become longer, 

 while both kinds become shorter at higher temperatures, indicates against 

 a coagulation at these low temperatures. According to MEIGS 3 we must 

 here also admit of an imbibition rigor, due to the formation of lactic acid, 

 and the different behavior of the two kinds of muscle depends upon a 

 different arrangement of their anatomical elements. 



The chemical rigor produced by different chemically active substances 

 is also produced, according to MEIGS as well as to v. FURTH and LENK, 

 upon a formation of acid, causing a chemical damage of the muscles, and 

 is to be considered as an imbibition rigor. 



As it is now generally admitted that the formation of lactic acid dur- 

 ing the death of the muscle is the cause of the muscle rigor, the question 

 arises, from what constituents of the muscle is this acid derived? The 

 most probable explanation is that the lactic acid is produced from the 

 glycogen, as certain investigators, such as NASSE and WERTHER, have 

 observed a decrease in the quantity of glycogen in rigor of the muscle. 



1 Journ. of Physiol., 39. 



2 Inagaki, Zeitschr. f. Biol., 48; Meigs, Journ. of Physiol., 24. 



* Vernon, Journ. of Physiol., 24; Meigs, Amer. Journ. of Physiol., 24. 



