Abstract
The distribution of sensory nerve fibres derived from the fundamental bronchial plexus shows a considerable difference in cat and rabbit, proportionate to the difference in the histological structure of the bronchial branches in their lungs.
The bronchial walls have the propria mucosae, the submucosa provided with bronchial glands, bronchial cartilages and adventitia far better developed in cat than in rabbit, while the muscularis is comparatively well developed in the latter, too. There is no mentionable difference in the construction of the bronchioli respiratorii and alveolar ducts and sacs of the two animals.
In cat, comparatively well-developed fundamental plexus containing ganglia of sympathetic nature of varying sizes is found in the adventitia of the large bronchial branches. Submucosal plexus is also derived from this plexus. It needs not be reiterated that the nerve bundles of the fundamental plexus extend further into the adventitia of medium- and small-sized bronchial branches. The bronchial plexus contains a rather large number of medullated thick sensory fibres, besides many fine vegetative fibres.
On the other hand, in rabbit, the nerve bundles of the fundamental plexus found in the very thin adventitia lining the muscularis of the bronchial branches are much finer and are found more sparsely scattered. The ganglia are also much smaller in number and size. But it should be noted that the nerve bundles contain quite a number of thick sensory fibres.
In the bronchial branches of cat, while the muscularis is only poorly developed, the propria mucosae is well developed. Perhaps owing to this one-sided development, while, in the muscularis, no such formations reminding of the sensory terminations Type I concerned with the blood pressurefalling reflex originating in very thick sensory fibres as found in the lungs of man and some other mammals could be detected, only a very few simple branched terminations being found formed by finer sensory fibres, in the well-developed propria mucosae, branched terminations originated in sensory fibres of variable sizes were frequently found, and often intraepithelial-fibres in the bronchial epithelium and in the gland ducts were formed by their terminal fibres. It may be mentioned with interest that such intraepithelial fibres were found particularly abundunt in the small-sized bronchial branches.
In rabbit, the propria mucosae of the bronchial branches is very poorly developed, and unbranched and simple branched terminations of thick sensory fibres were found rather more frequent in the better-developed muscularis. Intraepithelial fibres were not rare here, either.
In cat, only a very few of the sensory fibres end in the bronchioli respiratorii, but almost all the rather thick sensory fibres running thus far go farther into the alveolar ducts and sacs to end in unbranched or simple branched terminations therein. Some of these, however, run still farther into the pleura visceralis forming similar terminations in it.
In rabbit, a rather large number of simple branched terminations originated in thick sensory fibres could be found, with the terminal fibres ending in the muscularis or in the epithelium of the bronchioli respiratorii, but none was found to end in the interalveolar septa. But interestingly enough, unbranched and simple branched terminations were often located in the pleura visceralis of rabbit, too.
