474 ANIMAL PHYSIOLOGY. 
think the facts as they accumulate will more and more show, 
as has been already urged, that the influence of blood-pressure 
on the metabolic (nutritive) processes has been much over- 
estimated. They are not essential but concomitant in the 
highest animals. Turning to the case of muscle we find that 
when a skeletal muscle is tetanized the essential chemical and 
electrical phenomena are to be regarded as changes differing in 
degree only from those of the so-called resting state. There is 
more oxygen used, more carbonic anhydride excreted, etc. The 
change in form seems to be the least important from a physio- 
logical point of view. Now, while all this can go on in the 
absence of blood or even of oxygen, it can not take place with- 
out nerve influence or something simulating it. Cut the nerve 
of a muscle, and it undergoes fatty degeneration, and atrophies, 
True, this may be deferred, but not indefinitely, by the applica- 
tion of electricity, acting somewhat like a nerve itself, and in- 
ducing the approximately normal series of metabolic changes. 
If, then, the condition when not in contraction (rest) differs 
from the latter in all the essential metabolic changes in rate or 
degree only; and if the functional condition or accelerated 
metabolism is dependent on nerve influence, it seems reason- 
able to believe that in the resting condition the latter is not 
withheld. 
Certain forms of paralysis (e. g., hysterical) are not followed 
by atrophy. Why? Because in this form the nerve influence 
is still exerted. 
The recent investigations on the heart make such views as 
we are urging clearer still. It is known that section of the 
vagi leads to degeneration of the cardiac structure. We now 
know that this nerve contains fibers which have a diverse 
action on the metabolism of the heart, and that, according 
as the one or the other set is stimulated, so does the electri- 
cal condition vary; and everywhere, so far as known, a differ- 
ence in electrical conditions seems to be associated with a 
difference in metabolism, which may be one of degree only, 
perhaps, in many instances—still a difference. The facts as 
brought to light by experimental stimulation harmonize with 
the facts of degeneration of the cardiac tissue on section of the 
vagi; but this is only clear on the view we are now presenting, 
that the action of the nervous system is not only universal, 
but that it is constant; that function is not an isolated and 
independent condition of an organ or tissue, but a part of a 
long series of metabolic changes. It is true that one or more 
