APPLICATIONS OF THE GRAPHIC METHOD. 193 
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 will be borne in mind that muscle-fibers are tubes con- 
taining semifluid protoplasm, and that a coagulation of the 
latter must give rise to general rigor. This protoplasmic sub- 
stance 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 mus- 
cles by ammonium choride, etc. It resembles the globulins 
generally, but is less soluble in saline solutions than the globu- 
lin of blood (paraglobulin); is less tough than fibrin; has a 
very low coagulating point (55° 1o 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 
disorganization of the tissue. The reaction seems to be due to 
the formation of a kind of lactic acid, probably sarolactic; 
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 
anew 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 off 
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 atmos- 
phere free from 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 an 
explosion. 
After this the muscle becomes greatly changed physically : 
its elasticity and translucency are lost; there is absence of 
muscle-currents; if 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 
18 
