270 ANIMAL PHYSIOLOGY. 
failing heart, is also very suggestive. That. many disorders of 
the heart are coincident with periods of mental anguish or 
worry, and that in certain cases of severe mental application 
the heart’s rhythm has become very slow, also point to influ- 
ences of a central origin as greatly affecting the life-processes 
of this organ. 
It has been shown that the vagus nerve in some cold-blooded 
animals, as is probable also in the higher vertebrates, consists 
of two sets of fibers—those which are inhibitory proper and 
those which are not, but belong to the sympathetic system. 
Separate stimulation of the former favors nutritive pro- 
cesses, is preservative; of the latter, destructive. This has 
been expressed by saying that the former favors constructive 
(anabolic) metabolism; the latter destructive (katabolic) me- 
tabolism. It is assumed that all the metabolism of the body 
may be represented as made up of katabolic following anabolic 
processes. 
Whether such a view of metabolism expresses any more 
than a sort of general tendency of the chemistry of the body 
is doubtful. It is a very simple representation of what in all 
probability is extremely complex; and if it be implied that 
throughout the body certain steps are always taken upward in 
construction to bé always afterwards followed by certain down- 
ward destructive changes, we must reject it as too rigid and 
artificial a representation of natural processes. 
We think, however, that, upon all the evidence, pathological 
and clinical as well as physiological, the student may believe 
that the vagus nerve, like the other nerves of the body, accord- 
ing to our own theory, exercises a constant beneficial, guiding 
—let us say determining—influence over the metabolism of the 
organ it supplies; and we here suggest that, if this view were 
applied to the origin and course of cardiac disease, it would 
result in a gain to the science and art of medicine. 
THE ACCELERATOR (AUGMENTOR) NERVES OF THE HEART. 
It has been known for many years that in the dog, cat, rab- 
bit, and some other mammals, there were nerves proceeding 
from tertain of the ganglia of the sympathetic chain high up, 
stimulation of which led to an acceleration of the heart-beat. 
Very recently these nerves have been traced in a number of 
cold-blooded animals, and the whole subject placed on a broader 
and sounder basis. 
