156 THERMAL AND CHEMICAL CHANGES IN MUSCLE [CH. XIII. 



and in both cases also the muscle is electro-positive to uncontracted 

 muscle. 



Here, however, the analogy must end : for living contracted 

 muscle is irritable, dead muscle is not. Living contracted muscle is 

 more extensible than uncontracted muscle ; muscle in rigor mortis is 

 not so (see fig. 156, p. 128). The contraction of living muscle is 

 favoured by feeding it with a solution of dextrose, while the process 

 of rigor is hindered by the same solution. (F. S. Lee.) 



Our correct knowledge of the proteids of muscle and of the phenomena of rigor 

 mortis date from the year 1864, when Kiihne obtained muscle-plasma by subjecting 

 frozen frog's muscle to strong pressure. A good many years later I was successful 

 in repeating these experiments with mammalian muscle. By fractional heat coagula- 

 tion, and by their varying solubilities in neutral salts, I was able to separate four 

 different proteids in the muscle-plasma. 



1. A globulin precipitable by heat at 47 C. This is analogous to the cell- 

 globulin found in most protoplasmic structures. I gave it the name paramyosinogen. 



2. A proteid with many of the characters of a globulin, coagulable by heat at 

 56 C. ; and this I termed myosinogen. 



3. A globulin (myo-globulin), precipitable by heat at 63 C. 



4. An albumin similar in its properties to serum albumin is also present ; but 

 this and the myo-globulin only occur in quite small amounts. 



In addition to these, there is a small quantity of nuclei-proteid from the nuclei, 

 and in the red muscles haemoglobin is present ; the normal pigment of the so-called 

 pale muscles is termed myo-hcematin by MacMunn, and this is doubtless a derivative 

 of haemoglobin. 



The two most abundant and important proteids are the first two in the list, 

 namely, paramyosinogen and myosinogen. They occur in the proportion of about 

 1 to 4, and both enter into the formation of the muscle-clot (myosin). The myo- 

 globulin is possibly not a separate proteid, but only some myosinogen which has 

 escaped coagulation : the albumin is probably derived from adherent blood and 

 lymph. 



In 1895 v. Fiirth took up the subject. On the main question we are in substantial 

 agreement, namely, that in the muscle-plasma there are the two proteids just alluded 

 to, and that these both contribute to the formation of the muscle-clot. The main 

 points of difference between us are in the names of the proteids. He uses physio- 

 logical saline solution to extract the muscle-plasma, and this extract coagulates 

 spontaneously on standing ; he is doubtful whether a specific myosin-ferment brings 

 about the change. Paramyosinogen he terms myosin, and this passes directly into 

 the clotted condition (myosin-fibriri) ; but myosinogen, called myogen by v. Fiirth, 

 first passes into a soluble condition (coagulable by heat at the remarkably low 

 temperature of 40 C.) before it clots : the soluble stage he calls soluble myogen-fibrin, 

 and the clot myogen-fibrin. 



We may put this in a diagrammatic way as follows : 



Muscle Plasma. 



I 



Paramyosinogen. Myosinogen. 



(rayosin of v. Fiirth.) (myogen of v. Fiirth.) 



Soluble mj 



fibrin. Mvogre 



I 



Soluble myogen-fibrin. 

 Myosin-fibrin. Myogen-fibrin. 



I 

 Myosin or Muscle-clot, 



