THE STUDY OF MUSCLE PHYSIOLOGY. , 193 



The subject can be studied in some of its aspects to great ad- 

 vantage in an isolated individual muscle. 



Three changes in a muscle that has passed into death rigor 

 are constant and pronounced. The living muscle, either alka- 

 line or neutral in reaction, has become decidedly acid ; an 

 abundance of carbonic anhydride is suddenly given off ; and 

 myosin, a specific proteid, has been formed. That these phe- 

 nomena have some indissoluble connection with each other so 

 far as the first two at least are concerned, while not absolutely 

 certain, seems probable, as will be learned shortly. 



It wUl be borne in mind that muscle-fibers are tubes con- 

 taining semifluid protoplasm, and that a coagulation of the lat- 

 ter must give rise to general rigor. This protoplasmic substance 

 can be extracted at a low temperature from the muscles of the 

 frog, and, as the temperature rises, coagulates like blood, giving 

 rise to a clot (myosin) and muscle-serum, a fluid not very unlike 

 the serum of blood. 



This myosin can also be extracted from dead rigid muscles 

 by ammonium chloride, etc. It resembles the globulins gen- 

 erally, but is less soluble in saline solutions than the globulin 

 of blood (paraglobulin) ; is less tough than fibrin ; has a very 

 low coagulating point (55° to 60° C.) ; and is somewhat jelly- 

 like in appearance. The clotting of blood and of muscle is thus 

 analogous, myosin answering to fibrin, and there being a serum 

 in each case, both processes marking the permanent disorgani- 

 zation of the tissue. The reaction seems to be due to the forma- 

 tion of a kind of lactic acid, probably sarcolactic ; though 

 whether due to excessive production of this acid, on the death 

 of the muscle, which for some reason does not remain free in 

 the living muscle, or whether sarcolactic acid arises as a new 

 product, is uncertain. It is certain that the acid reaction of 

 dead muscle is not owing to carbonic acid, for the reddened 

 litmus does not change color on drying. 



That a muscle in action does use up oxygen and give, ofp 

 carbonic anhydride can be definitely proved ; though it is 

 equally clear that the life of a muscle is not dependent on a 

 constant supply of oxygen as is that of the individual, for a 

 muscle can live, even contract long and vigorously, in an atmosi- 

 phere free frem this gas, as in nitrogen. 



From the suddenness of the increase of carbonic anhydride, 

 the onset of death and rigor mortis has been compared to. ait 

 explosion. 



13 



