Abstract
The bronchial plexus found in the bronchial branches of hedgehog is far poorer in development than those in dog and goat and the nerve bundles run periadventitially, accompanying small ganglia frequently along their courses. The ganglion cells in them are provided with only indistinct nerve processes and barely show their multipolarity. The nerve bundles, interestingly enough, contain a larger relative number of thick sensory fibres than in goat and dog. These sensory fibres end in various types of terminations.
In the first place, I must mention the sensory terminations Type I concerned with the blood-pressure falling reflex found in a rather large number in the well-developed muscularis of the large and medium-sized bronchial branches. In hedgehog, these are in the form of unbranched and simple branched terminations formed by thick terminal fibres showing frequent and conspicuous change in size but devoid of such neurofibrillar leaves as found in such terminations in man. Sometimes, these terminations are of large complex branched type.
Subepithelial and intraepithelial sensory terminations are found in the bronchial branches of hedgehog as in those of man, Formosan macaque, dog, goat and bat, but in different construction and distribution density from those in the other animals. Very few of these terminations are found within the epithelium of the small-sized bronchial branches only, the greatest majority of them consisting of unbranched and simple branched terminations formed beneath the epithelium. The terminal fibres of these terminations are large or medium in size and show conspicuous change in size during their winding courses and usually end just beneath the epithelium in sharp or blunt points. Such subepithelial terminations are found only sporadically in the large- and the medium-sized bronchial branches but more abundantly and somewhat more complex in form in the small-sized branches. Some very simple glomerular terminations were also discovered.
Some of the sensory terminations are formed by exceptionally stout fibres, chiefly in the adventitia or beneath the epithelium of some small-sized bronchial branches only. In such terminations, a thick stem fibre after losing its myelin sheath further thickens into an enormously thick fibre which shows conspicuous change in size, and often divides into 2 or 3 terminal fibres which end either sharply or bluntly.
Subepithelial sensory fibres are not rare either in the bronchioli, but these are simpler in construction than those in the small-sized bronchial branches above, being limited to the simplest types of unbranched and simple branched terminations. Intraepithelial sensory fibres are also not rarely found here.
Very simply formed sensory terminations are found sporadically around the alveolar ducts and the alveolar sacs that is in the interalveolar connective tissue as in bat and goat.
A rather large number of sensory fibres are found running into the pleura visceralis of hedgehog. They terminate in unbranched and simple branched terminations formed of thick terminal fibres, which show frequent change in size and end sharply beneath the epithelium. Terminations formed of very thick fibres are not rare either in the pleura.
Small groups of smooth muscle fibres are sporadically found in the visceral pleura and sensory fibres are very often found running through or around them. These formations may possibly represent so many special receptors of some kind of stimuli.
