138 THERMAL AND CHEMICAL CHANGES IN' MUSCLE [CI1. XII. 



of lactic acid known as sarcolactic acid. The inorganic salts are 

 chiefly salts of potassium, especially potassium phosphate. 



The condition of dead muscle reminds one somewhat of contracted 

 muscle. Indeed, the similarity is so striking that Hermann pro- 

 pounded the idea that contracted muscle is muscle on the road to 

 death, the differences between the two being of degree only. He 

 considers that, on contraction, a hypothetical material termed inogen 

 is broken up into carbonic acid, sarcolactic acid, and myosin; on 

 death the same change occurs, only to a much more marked extent. 



This idea is a far-fetched one, but it is a useful reminder of the 

 similarities of the two cases. In chemical condition, contracted and 

 dead muscle are alike, so far as the formation of acid products is 

 concerned; there is, however, no evidence of any formation of a 

 muscle-clot (myosin) during the contraction of living muscle, as 

 there is in dead muscle. Then heat is produced in both cases, 

 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. 129, p. 111). 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 proteins 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 proteins 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 (myoglobulin), precipitable by heat at 63 C. 



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

 this and the myoglobulin only occur in quite small amounts. 



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

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

 pale muscles is termed myohcematin by MacMunn, and this is doubtless a derivative 

 of haemoglobin. 



The two most abundant and important proteins 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 probably derived from the adherent connective tissue and the albumin 

 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 proteins just alluded 

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

 points of diiference between us are in the names of the proteins. 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 



