The tracheal and bronchial parasympathetic ganglia in the cat were studied using the histochemical-tiocholine method of Koelle and Friedenwald and histological techniques. Intensively stained AChE-positive nerve structures, i.e., ganglia and nerve fibres on the wall of the trachea and bronchi, were observed. The ganglia were situated mainly on the dorso-lateral surface of these organs, but they were also present on the ventral surface. The largest ganglia were found in the vicinity of the vagus nerve branches and on the surface of the tracheal smooth muscle. Numerous ganglia (95–210) of different sizes (40 x 230 µm to 260 x 520 µm) and shapes (spindle, longitudinal, oval, elliptical and multiform) were interconnected by nerve fibres and formed a dense ganglionated plexus. The ganglia forming this nerve structure were located mainly on the level of intercartilaginous spaces. They received the nerve branches from the cervical and the upper thoracic branches of vagus nerve and cervical and upper thoracic segments of the sympathetic trunk. Similar AChE-positive ganglionated plexus containing 28–33 ganglia connected by nerve fibres was observed on the posterior wall of the bronchi.
Histological investigations confirmed the presence of fascicles of nerve fibers and nerve cells aggregations in the external membrane of the trachea and bronchi. The ganglia consisted of 2–25 cells on the cross-section. They were located mainly on the level of intercartilaginous spaces and contained (except ganglionic neurocytes, nerve fibres) satellite cells and small blood vessels. All the ganglia had thin connective capsule.