NERVE TERMINATIONS IN LUNG OF RABBIT 119 
Plesehko (’97), by staining with methylene-blue, found motor 
terminations in the smooth muscle of the trachea. He also 
figured and described ganglion cells with processes which pass 
to the smooth muscle bundles, there to divide into fine fibers 
which terminate in the individual muscle cells. These ganglion 
cells are surrounded by pericellular plexuses of fine varicosed fibers 
formed by the splitting up of nerve processes which apparently 
are given off from the vagus nerve. ‘There is present, therefore, 
in the trachea the typical relation of preganglionic (vagus) 
fibers to the terminal ganglionic cells with their postganglionic 
fibers. The latter are represented by the axones which pass to 
the trachealis muscle, there to ramify in the manner above 
described. 
According to Miller (18), the musculature of the bronchi is a 
direct continuation of the musculature of the trachea. It will 
appear that the same pattern of innervation also holds for the 
smooth muscle of the bronchi and their branches that is present 
in the trachea. 
Clusters of ganglionic cells (figs. 8 and 9) are found along the 
primary bronchi and their larger branches. These clusters 
constitute small ganglia which are usually located along the 
course of the larger nerve bundles on the wall of the bronchial 
tree. The larger clusters of cells, which are located nearer to 
the hilum of the lung, are surrounded by a connective-tissue 
capsule. This capsule also contains frequently a fairly large 
nerve trunk, which is composed of both myelinated and unmye- 
linated fibers. The myelinated fibers are of three sizes, corre- 
sponding to the description given by Chase and Ranson (’14) 
of the fibers in the vagus nerve. There are a few myelinated 
fibers of large size and more numerous myelinated fibers of small 
and medium size. 
It has been long known that in the walls of the larger bronchi 
the muscle occurs in bands. In the smaller subdivisions where 
no plates of cartilage are present, the muscle is said to constitute 
a continuous sheet. No muscle fibers are found distal to the 
alveolar ducts, but there isa sphincter-like band at the extremities 
of these ducts, surrounding the openings into the atria, as was 
THE JOURNAL OF COMPARATIVE NEUROLOGY, VOL. 33, NO. 2 
