Sensory innervation of the motor organs of the foot.

Abstract

In the motor organs of the foot of the 3rd month human embryo, corpuscular terminations have been found in a large number. Most of these belong to the Golgi-Mazzoni corpuscles, the Pacinian bodies being found in far smaller number.Pacinian bodies are mostly still very small in size as well as underdeveloping in structure. The inner bulb is generally thin and slender, but sometimes broad and swollen, the specific nuclei therein being still immature. The connective tissue lamellae covering the inner bulb number 3-4 pieces only. A comparatively thick sensory fiber entering into the inner bulb gradually increases in size and, without branching, ends bluntly near the distal pole of the inner bulb. Interestingly enough, Pacinian bodies of compound type mostly consisting in two small bodies encased in a common lamellar capsule have not rarely been found in the motor organs, especially in the dorsal side of the foot.Golgi-Mazzoni bodies, well-developed in the 3rd month embryo, are recognized in a rather large number in various places of the motor organs, especially in the surroundings of the metatarsal bones and sesamoid bones. These are of cylindrical form and divided into small-sized and large-sized ones.In small-sized bodies, the inner bulb contains single row of specific nuclei in its periphery and is surrounded by a broad transparent layer, which is covered by a single circular layer of fibrocytes and an outermost single layer of elongated connective tissue cells. A thick nerve fiber running into the inner bulb proceeds along its longer axis and ends bluntly near the distal pole of the inner bulb, without branching. In large sized bodies, the inner bulb is swollen and richer in specific nuclei, but the transparent layer is rather ill-developed. A sensory fiber toward each body is almost of medium size and ends sharply or bluntly in the inner bulb, without branching.Golgi-Mazzoni bodies gathered in groups were recognized in the foot motor organs, especially frequently within or along the periosteum of the metatarsal as well as the sesamoid bones. The sensory fibers entering into the individual bodies are of large or medium, sometimes of small size and derived from the separate fibers respectively, but rarely they consist of terminal branches coming out from one stem fiber. Such groups are here consisting of 2-4, sometimes of 5 Golgi-Mazzoni bodies, and they are divided into two types, the one composed of small-sized and the other of large-sized bodies.Besides, simply branched terminations being ill-developed are found in the periosteum of the foot bones in a never large number. Further, there are found in the periosteum of the metatarsal bones rather complex, branched terminations here and there, though they are composed of finer branch fibers, which frequently arrive at the inner layer of the periosteum and mostly end in sharp points. On the contrary, here in the periosteum no such a branched termination, as composed of powerfully thick branch fibers and presumed to be specific to the periosteum could be found.Any muscle or tendon spindle could not be found in the foot of the 3rd month embryo.