On Innervation of Pig Penis

Abstract

The termination of vegetative nerve fibres is represented by STÖHR's terminalreticulum in distal part of pig penis too.
The n. dorsalis penis in pig is composed of a large number of medullated sensory fibres and a small number of non-medullated vegetative fibres, the former comprising 2/3 of thick fibres and 1/3 of thin fibres in quantity. The thick fibres probably pass into such terminations to receive sexual sensation as the below-described specific branched terminations, genital nerve bodies and PACINIAN bodies, while the thin fibres end in simple branched terminations to receive pain and other general sensations.
1. The PACINIAN bodies are formed also in the distal part of the penis along the tunica albuginea of the corpus cavernosum penis. They are characteristically much smaller than those in man, with few lamellae and a branched sensory termination within the spacious inner bulb.
2. The genital nerve bodies are classifiable into 3 types as by man, but the type II is again divisible into 2 sub-classes. The essence of the inner bulb is represented by a differentiation of SCHWANN's sheeth, showing the synzytial nature constituted of a granulated ground substance and specific cell nuclei. The type I bodies are chiefly capsulated, found in the papillae and tunica propria of the glans penis and are characterized by showing a complex glomerular arrangement of small fibres all over the space in the inner bulb.
The type II sub-class 1 is also capsulated and found in the same positions, but only the central part of the inner bulb, often including more or less also its peripheral part, is occupied by a branched sensory termination. Ditto sub-class 2 is generally small in size, by which a thick fibre passes over into a rather simple branched termination in the inner bulb inside the capsule, forming specific small terminal bodies of various sizes in the course or at the tips of the terminal branches.
Type III is found outside the tunica albuginea of the corpora cavernosa or between the outer and inner layers thereof. Genital bodies belonging hereto are generally non-capsulated and are poor in specific cell nuclei. Their nerve terminations are represented by the branched type as in type II sub-class 1. Those outside the tunica albuginea show more complexity than those between the layers.
3. Simple branched terminations. These originate in finer medullated fibres and are represented as the endings with a few simple nerve branches beneath the epithelium.
4. Specific complex branched terminations. These are not observed in human genitals. They give the impression of plexus-like terminations originating in a number of medullated fibres, but they are in reality complicated branched terminations based upon only two or three thick fibres. The terminal state of the terminal branches is so characteristic, that their tips often pass into round or berry-shaped bodies in various sizes formed by neurofibril distension or sometimes into genital nerve bodies. Besides, they show in their course very peculiar neurofibril expansions or glemerular formations.