RIGOR MORTIS. 589 



fermentative rigor, because it seems to depend in part on the action of 

 an enzyme. A muscle may also become stiff or other reasons. The 

 muscles may become momentarily stiff by warming, in the case of frogs 

 to 40, in mammalia to 48-50, and in birds to 53 C. Distilled water 

 may also produce a rigor in the muscles (water-rigor). Acids, even very 

 weak ones, such as carbon dioxide, may quickly produce a rigor (acid- 

 rigor), or hasten its appearance. A number of chemically different 

 substances, such as chloroform, ether, alcohol, ethereal oils, caffeine, 

 and many alkaloids, produce a similar effect. 



When the muscle passes into 'rigor mortis it becomes shorter and 

 thicker, harder and non-transparent, and less ductile. The acid part 

 of the amphoteric reaction becomes stronger, which is explained by most 

 investigators by the assumption of a formation of lactic acid. There is 

 hardly any doubt that this increase in acidity may at least in part be 

 due to a transformation of a part of the diphosphate into monophosphate 

 by the lactic acid. The statements as to whether in the rigor mortis 

 muscles, besides acid phosphate also free lactic acid exists or not are 

 rather contradictory; 1 that an acid formation precedes the rigor is gen- 

 erally admitted and this acid formation is now accepted as being in close 

 relation to the rigor. While we used to consider the appearance of a clot 

 consisting of myosin (KUHNE) or of myogen- and myosin fibrin (v. FURTH) 

 as the essential moment for the rigor, we now admit, based upon the 

 investigations of MEIGS, v. FURTH and LENK, 2 that the most essential 

 factor is the imbibition of the disdiaclasts, which become broader or 

 shorter, by their taking up of water from the sarcolemma fluid and this 

 action produced by the acid formation. This view stands in accord with 

 the experience on the imbibition of colloids and muscles in water or salt 

 solutions, in the presence and absence of acid, as well as the fact that the 

 rigor can be retarded by the artificial circulation of blood or by the action 

 of salt solutions, namely by those which contain small amounts of 

 NaHCOs. This also agrees well with the old experience, that the muscle 

 work, which is also connected with a formation of acid, accelerates the 

 appearance of rigor. 



On further post-mortal changes, namely by a further accumulation 

 of acid, a progressive coagulation of the proteins gradually occurs. In 

 this coagulation the ability of the colloid systems to imbibe water 



1 It is impossible to enter into the details of the disputed theories as to the reac- 

 tion of the muscles, etc. We shall only refer to the works of Rohmann, Pfliiger's 

 Arch., 50 and 55, and HefTter, Arch. f. exp. Path. u. Pharm., 31 and 38. These 

 works contain also the researches of the earlier investigators more or less completely. 



2 Meigs, Journ. of Physiol. 39 and especially, Amer. Journ. of Physiol., 24 and 

 26; v. Fiirth and Lenk, Bioch. Zeitschr., 33, and Wien. klin. Wochenschr., 24 (1911). 



