APPLICATIONS OF THE GRAPHIC METHOD. 195 
There is a coloring matter in muscle, more abundant in the 
red muscles of certain animals than the pale, allied to hemo- 
globin, if not identical with that body. 
It may be stated as a fact, the exact significance of which 
is unknown, that during contraction the extractives soluble in 
water decrease, while those soluble in alcohol increase. 
It will, however, be very plain, from what has been stated 
in this section, that life processes and chemical changes are 
closely associated, and to realize this is worth much to the 
student of Nature. 
THERMAL CHANGES IN THE CONTRACTING MUSCLE. 
Since very marked chemical changes accompany muscular 
contraction, it might be‘expected that there would be some 
modification in temperature, and probably in the direction of 
elevation. Experiment proves this to be the case. If a ther- 
mometer finely graduated be kept among the muscles of the 
limb of a mammal during the contractions that follow the 
stimulation of the main nerve, a decided rise of temperature 
may be noted during the prolonged tetanus that may be thus 
originated. True, during the contraction of a set of muscles 
under such circumstances, there is a possible fallacy, from the 
excess of blood going to the parts owing to dilatation of the 
blood-vessels, which it would be necessary to exclude—i. e., we 
must either ascertain that such does not take place, or take it 
into account as a factor in the causation of the rise of tempera- 
ture. However, by using a delicate thermopyle, a muscle to 
which no blood passes may be shown to grow warmer during 
contraction. 
But why should a muscle when at rest, as may be shown, 
maintain a certain temperature, unless chemical changes are 
constantly taking place? As already stated, such is the case, 
and the rise on passing into tetanus is simply an expression of 
increased chemical action. 
What is the nature of the combustion originating this heat ? 
Are certain crude materials withdrawn from the blood and 
burned up directly in the muscle-substance; or is the muscle 
‘itself continuously building up and tearing down its own sub- 
stance, all of which implies oxidation ? 
All attempts to explain the facts apart from the latter view 
have been unsuccessful, and we are forced to conclude that 
such is the synoptical statement of the life-history of muscle. 
