On Sensory Innervation of Larynx in Goat

Abstract

The sensory nerve distribution in the mucous membrane of the goat's larynx is very rich in the laryngeal side but much poorer in the lingual side of the epiglottis, in proportion to the development of the submucosal and the proprial plexus in the sides, becomes ever poorer as we go down from the basis of the epiglottis along the mucous membrane of the laryngeal wall outside the epiglottis, and drastically diminishes in the lower portion of the larynx beyond the rima glottidis. The above finding is little different from that on the larynges of man and other animals. The sensory terminations in the goat's larynx, however, are incomparably poorer than in man, slightly poorer than in dog, but rather better than in rabbit in their development. It is of interest that their terminal mode shows some peculiarities specific to the animals.
No sensory terminations related with the HERING's blood pressure falling reflex as found in the human and canine larynges were ever found in goat's larynx, as in the case with rabbit, but simple glomerular terminations, nerver found in the rabbit's larynx, were found in my caprine specimens, though in as small number as in the dog's larynx. No sensory terminations composed of such enormous thick fibres as peculiar to the rabbit's larynx were to be found in the goat's as little as in the dog's larynx. Thus, the sensory terminations found in the goat's larynx consist in subepithelial and intraepithelial branched terminations originated in medium-sized fibres and not a few simple glomerular terminations.
In the laryngeal side of the epiglottis, somewhat rather complex branched terminations spread out over a considerable area subepithelially are found in formation. Their terminal fibres often show perceptible change in size in their courses and sometimes form intraepithelial fibres. Complex branched terminations are not rare either; the terminal fibres of these sometimes have small glomerular bodies formed of fine branched fibres at their ends. The intraepithelial fibres usually belong in the simple branched type and in very many cases run up into the very surface layer of the epithelium.
Branched terminations may be found in the lingual side of the epiglottis too, but these are far smaller in number and simpler in from than those in the laryngeal side. No intraepithelial fibres were found here.
In the laryngeal mucous membrane outside the epiglottis, especially, above the rima glottidis somewhat rather complex subepithelial branched terminations and intraepithelial fibres may be found, but in the rima the terminations are considerably worse developed. In the plica vocalis, however, the sensory terminations are better developed at least than in dog, simple branched terminations and intraepithelial fibres also being found in small numbers. In the pars intracartilaginea of the rima glottidis, sensory terminations may be found in a larger number and in more complex forms than in the plica vocalis.
It may be that the stratified flat epithelium lining not only the laryngeal side of the epiglottis but the wall of the larynx down to the rima glottidis as well in goat and in dog admits of such a formation, so that an abundance of taste-buds are found here, in a number larger than in dog and of course larger than in man. The nerves supplied to these taste-buds, as in the dog's larynx, do not show difference in quantity by locality, as seen in the case with man, where they are gradually distributed as we go down from the upper parts of the larynx toward its lower portions. Thus, in the goat's laryngeal wall, taste-buds devoid of nerve supply and those comparatively well supplied with sensory fibres are found in mixed coexistence in the same place. Comparatively complex proprial plexus is found in the propria beneath the taste-buds, and the sensory fibres from the plexus mostly run toward the taste-buds to end in branched terminations therein, some of them running further intra- and extragemmally.