APPLICATIONS OF THE GRAPHIC METHOD. 208 
There are some advantages in investigating changes in tem- 
perature by the graphic method. Curves from a muscle-nerve 
preparation show that elevation of temperature shortens ‘the 
latent period and the curve of contraction. Lowering the tem- 
perature has an effect exactly opposite, as might be supposed, 
and these changes take place in the muscles of hoth cold-blooded 
and warm-blooded animals, though more marked in the latter. 
The modifications evident to the eye are accompanied by 
others, chemical in nature, and a comparison of these shows 
that the rapidity and force of the muscular contraction run 
parallel with the rapidity and extent of the chemical changes. 
Certain drugs also modify the form of the muscle-curve very 
greatly, so that it appears that the molecular action which un- 
derlies all the phenomena of muscle and nerve (for what has 
been said of muscle applies also to nerve, if we substitute 
nervous impulse for contraction) can go on only within those 
narrow bounds which, one realizes more and more in the study 
of physiology, are set to the activities of living things. 
What is the Intimate Nature of Muscular and Nervous Action ?— 
The answers to these questions, to which some allusion has been 
already made, are by no means certain. Some believe that, 
since the nitrogeneous waste of the body,if judged by the urea 
of the urine, is not augmented, some carbohydrate breaks up, 
which would be in accord with the fact that the gaseous inter- 
change of the body generally is increased during exercise, espe- 
cially the excretion of carbonic anhydride. 
Upon the whole, however, such a view does not harmonize 
well with the behavior of protoplasm generally, and it is possi- 
ble to conceive of other processes which would give rise to car- 
bonic anhydride and additional waste products. 
It seems to be likely that the muscle protoplasm builds up 
and breaks down as a whole; that this is constantly going on; 
and that the oxygen which is stored away (intra-molecular) 
suffices for immediate use; but that when a contraction takes 
place all the chemical processes are heightened, so that we 
may conceive most naturally of the various aspects of muscular 
life as phases of a whole, the parts of which are closely linked 
together. 
Another unsettled point is the explanation of the fact that 
a nerve, when stimulated nearer the nerve-center, gives rise to a 
more marked contraction, with the same stimulus than when 
excited nearer the muscle. 
Some suppose that the change that in a nerve constitutes an 
