194 COMPARATIVE PHYSIOLOGY. 



After this the rauscle becomes greatly changed physically ; 

 its elasticity and translucency are lost ; there is absence of 

 muscle-currents ; it is wholly unirritable, is less extensible — it 

 is, as before stated, firmer — it is dead. 



But these fundamental phenomena, the increase of carbonic 

 anhydride and the acid reaction, are observable after prolonged 

 tetanus. It was, therefore — ^putting all the facts together that 

 we now refer to and others, not forgetting that a muscle is 

 always respiring, inhaling oxygen, and exhaling carbonic an- 

 hydride — not unreasonable to conclude that normal tetanus 

 and rigor mortis were but exaggerated conditions of a natural 

 state. The coagulation of the muscle protoplasm {plasma), 

 giving rise to myosin, was, however, a serious obstacle to the 

 adoption of this view. But it has very recently been urged 

 with great plausibility that an old view is correct, viz., that 

 rigor mortis (contracture) is the last act of muscle-life ; it is, in 

 fact, a prolonged tetanus or contracture, ending in most cases, 

 though not all, in coagulation of the myosin. This state can 

 be induced and recovered from in favorable cases by cutting 

 off the blood from a part by ligature, and later readmitting it 

 to the starving region. It has been suggested that the prod- 

 ucts of the muscle-waste, usually washed away by the blood- 

 stream, in such an experiment and after death, collect and act 

 as a stimulant to the muscle, causing it to remain in permanent 

 contraction. 



The other constituents of dead muscle and their relative 

 properties may be learned from the following table (Von Bibra) : 



Water 744-5 



Solids : Myosin, elastic substance, etc., in- 

 soluble in water 155'4 



Soluble proteids 19-3 



Gelatin 207 



Extractives and salts 37'1 



Fats 23-0 



255-5— 235-5 



Total 1,000 



Among the extractives of muscle very important is creatin 

 (-2 to -3 per cent), a nitrogenous crystalline body. Certain 

 allied forms, as xanthin, hypoxanthiu (sarkin), carnin, taurin, 

 and uric acid,- are also found. 



Glycogen (animal starch), very abundant in all the tissues, 



