THE CIRCULATION OF THE BLOOD. O71 
There are variations in the distribution of these nerves for 
different groups of animals, but it will suffice if we indicate 
their course in a general way, without special reference to the 
variations for each animal group: 1. These nerves emerge from 
the spinal cord (upper dorsal region), and proceed upward 
before being distributed to the heart. 2, They may leave for 
their cardiac destination either at (a) the first thoracic (or basal 
cardiac ganglion, as it might be named in this case), (b) the in- 
ferior cervical ganglion, (c) the annulus of Vieussens, or (d) the 
middle cervical ganglion, 
Accelerator Center in Medulla. 
Superior Cervical Ganglion. 
Middle Cervical Ganglion. 
Spinal Cord. 
Inferior Cervical Ganglion. 
Region of First Rib. 
Accelerator Nerves. 
Fic. 241.—Diagram to illustrate the origin, course, etc., of accelerator impulses. It will be 
understood that this is intended to indicate the general plan, and not precisely what takes 
place in any one animal. Thus, while the accelerator nerves may arise in this way, it is 
not meant to be implied that the heart is actually epee by three nerves of such origin 
‘im any case. The arrows, as before, indicate the path of the impulses. 
- 
Their course has been traced by physiological methods; thus 
it has been found that, in all animals examined, stimulation 
of the spinal cord or the various parts mentioned above, or 
nerve branches from them, gave rise either to acceleration of 
