On the innervation of the ventral abdominal wall in 10th month human embryo.

Abstract

In the ventral abdominal wall of the 10th month human embryo, the sensory nerve fibres in the subserous layer pass into the non-corpusclar and the corpusclar terminations. The formers are far superior to the latters in quantity and divided into the non-ramified and the ramified endings. The latters are likely divided into the Pacinian bodies and the special ones discovered by me. The Pacinian bodies are found rarely and only in the subserous tissue, but develope almost to the rough completion. The special bodies distribute not only in the subserous tissue, but also in other tissues, even much more than the Pacinian bodies, are composed of a good developed inner lulb and a few lamellae surrounding it, and often divide itself into two bodies, to show a twin-like formation. Further-more there is seen as a appendage of this body the formation of a cylinder-body termed the vestibulum corpusculi. The inner bulb occupies the half or sometimes nearly the whole part of the body, and consists of many special nuclei and granular and darkreddish stainable substances, showing no cell-border like a syncytium. The vestibulum is composed of the proper substance which contains a few of special nuclei of syncytial nature and the connective tissue capsule. A medullated fibre penetrates the vestivulum after losing its myelin and takes a wavy course in it. Reaching the inner bulb of the proper body, the nerve fibre takes in general suddenly the straight course and end finally with a clubbed termination. But some of the nerve fibres show the change of thickness and the peculiar winding course, and often divide into some branches. The muscle-spindles in the abdominal muscles in the 01th month human embryo are composed of a few Weismann's fibres and a thick connective tissue capsule like those in other striated muscles, and found in m. rectus abd. most numerous and well developed. In comparison with the muscle-spindles in the tongue-and the thenar of the same month embryo, the abdominal muscle-spindles may be several times in number and much better developed. The nuclei in the Weismann's fibres are divided into the proper nuclei and the special nuclei. The formers are oval and rich in chromatin, while the latters are round and poor in chromatin, and gather in the swelling of the spindle (central nuclei gathering by Felix and etc.). So the swelling formation may be caused, by their gathering. Accordingly, the connective tissue capsule becomes very thin in this place and Weismann's fibres also become so degenerative, that they come in places to disappear incontinously. It seems that the special nuclei might grow from the Schwann's nuclei belonging to the sensory nerve fibres, like the special nuclei in the inner bulb of the terminal body. It is not too much to say that the nerve fibres for the muscle-spindle are almost occupied by the sensory fibres, because the motor and the vege-tative fibres are far inferior to the formers. The sensory terminations show the very complicated figures as well as the regular innervation and are divided into the chief and the accessory terminations. A thick medullated fibre for the muscle-spindle loses its medullary sheath and divides into several branches, most of which advance to the nuclei gathering, to ramify furthermore. This is the chief termination. On the contrary, there are a few branches which do not enter the nuclei gathering, but run along the Weismann's fibres forward and terminate finally by encircling them. This is the accessory termination, which is far inferior to the chief termination in scale. In the cheif termination, the nerve branches to the nuclei gathering run with their subbranches along the sarcolemm spirally or looplikely, , or often quite irregularly and terminate with each peculiar end-apparatus either epilemmally or hypolemmally. The terminal endings sometimes. remarkably terminate in contact with the special cell nuclei.