454 Proceedings of the Boyal Society 
four minor plexuses referred to supply branches which pursue a 
definite direction. Thus the branches from the plexus, situated 
between the pulmonary artery and aorta, and between the former 
and the right auricle, proceed in a spiral direction from right to 
left downwards, so that they cross the muscular fibres composing 
the ventricles. The same may be said of the branches proceeding 
from the plexuses occurring on the posterior surface of the auricles 
and on the posterior coronary sinus. By this arrangement the 
nerves distributed to the heart are brought into intimate contact 
not only with the muscular fibres, but also with the blood-vessels ; 
and this is important, as it is on the latter that the ganglia are most 
frequently detected. 
In the third and concluding part of the investigation, the en- 
largements and fusiform swellings figured by Scarpa* and Leef 
have been examined microscopically, and their precise nature ascer- 
tained. The hearts examined for this purpose were numerous, and 
consisted, among others, of those of man, the horse, ox, camel, 
heifer, dog, panther, deer, seal, and pig. 
The ganglia occur as irregularly shaped enlargements, having 
three, four, five or more nerves connected with them. Sometimes 
they appear as simple dilatations occurring on the nerves as they 
cross the vessels. They are most numerous on the posterior coronary 
sinus, where they form a continuous network not hitherto described ; 
but they are also to be found in large quantities on the vessels and 
throughout the substance of the heart generally. 
When a ganglion, with several nerves proceeding from it, is de- 
tached and treated with carmine and glycerine, it is found, on 
microscopic examination, to be crowded with nerve-cells, the poles 
of which are directed towards the nerves themselves. When one of 
the swellings or dilatations which occur on the nerves, as they cross 
the vessels, is similarly treated, the nerve-cells are seen to form an 
oval patch corresponding in shape with the dilatation, and the poles 
of the cells are directed, as a rule, in the direction of the nerve 
trunk. In some instances the nerves terminate in bulbous expan- 
sions, and on such occasions the expansions in question are crowded 
with nerve-cells, the poles of which are directed towards the attached 
*■ Tabulse Neurologicfe, fob 1794, 
t Phil. Trans., 1849. 
