Ganglion

“ The thoracic ganglion expands, on either side of the oesophagus, into a mass which extends nearly as far forward as the apex of the cerebral ganglion. These lateral masses give off nerves to the appendages. From the back of the transverse portion proceed three nerves. The median nerve passes above the generative organs, and soon branches into two nerves which presently swell out to form ganglia of considerable size, beyond which they soon join again and give off an anastomosing network of nerve-fibres. The lateral nerves immediately branch. ”

“ Considerable differentiation has already set in in the constitution of the ganglia themselves, which are composed of an outer mass of ganglion cells enclosing a kernel of nerve fibres, which lie on the inner side and connect the successive ganglia. There are still distinct thoracic and abdominal ganglia for each segment, and there is also a pair of separate ganglion for the cheliceræ, which assists, however, in forming the œsophageal commissures. ”

“ I do not know what it is; all is solid when the ganglion is cut. I think then by admitting, even to a certain extent, the internal arrangement that this author has observed in the ganglions, we cannot describe these organs in the point of view in which he has presented them.
We know but little of the alterations that diseases produce in the texture of the ganglions. I have already many times examined in diseases of the heart, of the liver, of the stomach, the intestines, the ganglions that send nerves to these viscera ”

“ It sends a short branch to the recurrent lacrimalis of the sympathetic system. At this point there is formed a reddish-yellow ganglion, the petrosal ganglion, which is similar to the petrosal ganglion of mammals. Frequently it is found close below the large superior cervical nerve ganglion. The petrosal ganglion is frequently connected by special fibers with the cervical nerve ganglion, the large superior cervical nerve ganglion and the ganglion radicis vagi. The glosso-pharyngeus is divided into the following branches. ”

“ Again, while it is true that no ganglia are known to exist in the margins of the Scyphomedusæ outside of the ganglia in the marginal bodies, yet, ganglion cells and nerve fibers are found in the subumbral part of the margin as well as in the rest of the umbrella. And as I know no reason why scattered ganglion cells may not function as ganglia, it is possible that the contractions in question were spontaneous. ”

“ If we follow the course of the motor nerves in a {103} direction away from the muscles to which they are distributed, they will be found, sooner or later, to terminate in ganglia (fig. 24 A, gl.c; fig. 25, gn. 1–13) . A ganglion is a body which is in great measure composed of nerve fibres; but, interspersed among these, or disposed around them, there are peculiar structures, which are termed ganglionic corpuscles, or nerve cells (fig. 24, B) . ”

“ Diagram of the ganglia of Nucula castrensis, reconstructed from serial sections. The probable position of the connectives is shown and the proportionate distances between ganglia are given. The upper ganglion is the cerebro-pleural with large nerves leading off from the ganglion which is itself lobed into four chief lobes. The pedal ganglion is next. In section the pedal ganglion at one place seems to be made up of four parts which may correspond to four connectives from the cerebro-pleural although only one pair of connectives was clearly determined. ”

“ The ganglia are nerve centers which receive and generate impulses; the nerve trunks are filaments which convey impulses. The gray matter of the cord described above is the ganglionic portion, and the outer white matter is made up of nerve fibers which convey impulses from one part of the cord to another, or to and from the brain.
The nerves that have their roots in the spinal cord superiorly, are sensory; that is, they convey the sensory impulses from the periphery to the cord ganglion and to the brain. They have a ganglion just outside the cord. ”

“ These ganglion cells lie chiefly in the sub-pericardial tissue in the posterior wall of the auricles between and around the orifices of the venae cavae and pulmonary veins and between the aorta and pulmonary artery. The minute structure of these ganglia and the terminations of the nerves have been studied particularly by Dogiel. The inhibitory fibres arise from a centre in the spinal bulb which is in tonic action and constantly bridles the heart's action. When the vagi are divided the frequency of the heart increases and the blood pressure rises. ”

“ Why has not nature placed ganglions in the nerves of the extremities as in those of the other parts? If there is only a division of the nerve into finer filaments, in the ganglion, why is there not a proportion between the filaments that enter on one side, and those that go out at the opposite? ”

“ Along the under side of each ganglion there is a very thick layer of cells, continuous behind, with the layer of ganglion cells which is placed on the under surface of the œsophageal commissures. These cells have, moreover, an arrangement very similar to that in the ventral cords, so that a section through the supra-œsophageal ganglia has an obvious resemblance to what would be the appearance of a section through the united ventral cords. On the outer borders of the ganglia the cells extend upwards, but they end on about the level of the optic nerve (fig. 19D) . ”

“ The nervous system consists of a cerebral ganglion in the head, a conspicuous ventral ganglion in the trunk, and of lateral commissures uniting these ganglia on each side. The whole of this system has retained its primitive connexion with the ectoderm. The cerebral ganglion also gives off a nerve on each side to a pair of small-ganglia, united by a median commissure, which have sunk into and control the muscles of the head. As in other animals there is a minute but extensive nervous plexus, which permeates the whole body and takes its origin from the chief ganglia. ”

“ As it is in the nature of a single ganglion to be affected only by special stimuli from particular 424 parts of the body; so it is in the nature of a single ruler to be swayed in his acts by exclusive personal or class interests. As it is in the nature of an aggregation of ganglia, connected with the primary one, to convey to it a greater variety of influences from more numerous organs, and thus to make its acts conform to more numerous requirements ”

“ At the cephalic end of the cerebro-pleural ganglion the large ganglionic cords are in evidence. A little distance from the cephalic end on the dorsal side there are quite large groups of cells down from the surface and surrounded by nerve fibers. The course of the fibers here is quite complex. On the ventral lateral sides of the ganglia are paired light areas of fibers which may be traced into the fibers of the ganglionic cords. ”

“ They proceed from a small ganglion or enlargement in the upper part of the neck, or from a collection of minute ganglia within the abdomen. They go to the heart, and it beats; and to the stomach, and it digests. They form a net-work round each vessel, and the frame is nourished and built up. They are destitute of sensation, and they are perfectly beyond the control of the will. ”

“ In respect to the nervous system, there are no diagnostic characters; there are, however, not as many as two pairs of ganglia to a segment. The brain is well developed, sending a pair of slender nerves to the small eyes. The ganglia of the segment bearing the first pair of legs is fused with the subœsophageal ganglion. Grassi was unable to detect a true sympathetic system, but he suspects the existence of a very small frontal ganglion.
The slender dorsal vessel, provided with ostia and valvules, pulsates along the entire length of the trunk; an aorta passes into the head. ”

“ It is covered deeply with muscles. This portion is known as the cervical sympathetic nerve trunk. A trunk lies on each side of the cervical vertebræ. The large thoracic nerve ganglion, the inferior cervical, is located along this trunk at the entrance of the thorax. From this ganglion there is given off the recurrent cardiacus which supplies the heart. The end branches of the sympathetic nerve trunk blend with the pneumogastric nerve. The inferior nerve ganglion is the ganglion cardiacum. Near this ganglion is found a nerve plexus in which there are imbedded peripherlistic ganglia. ”

“ They are met with in young adults who follow laborious occupations or who indulge in athletics, and they cause stiffness, discomfort, and impairment of the use of the limb. A ganglion is sometimes met with on the median aspect of the head of the metatarsal bone of the great toe and may be the cause of considerable suffering ”

“ The nerve fibers that connect with a ganglion are not structurally continuous with the cells of the ganglion, so that a sense impression or a feeling impression is conveyed from one ganglion to another by fibers which are discontinuous at the ganglion. ”

“ The acoustic nerve, which next to the optic is the thickest in the body, divides soon after entering the tibia into two branches, one almost immediately forming a ganglion, the supra-tympanal ganglion, the other passing down to the tympanum, where it expands into an elongated flat ganglion, the organ of Siebold (Fig. 293) , and closely applied to the anterior tracheæ. ”

“ They become more elongated and fibrous, their main attachment to the neural tube being still at its posterior (dorsal) surface, near which they first appeared. Later still they become applied closely to the sides of the neural tube and send fibres to it below as well as above. Below (ventral to) the neural tube a ganglion appears, forming only a slight swelling, but containing a number of characteristic nerve-cells. The ganglion is apparently formed just below the junction of the anterior and posterior roots, though probably the fibres of the two roots do not mix till below it. ”

“ Close to each cerebral ganglion is a pleural ganglion, and each is connected by a long nerve with the pedal ganglion of the same side, the two connectives of either side being united in the distal art of their course. ”

“ In birds then, the upper cervical ganglion is that which in man the opthalmic ganglion, the ganglion of Mekel and others are. This disposition, which is natural in birds, agrees with what I have sometimes observed in the human subject between the first lumbar and the last thoracic ganglions, as well as between the lumbar and sacral ganglions themselves. 2dly, In many instances there are no ganglions in the spot where the pretended sympathetic nerve communicates with the spinal marrow. ”

“ There is a certain part of the spinal cord, at the top of the neck, which is what we call a ganglion, that is, a centre of nervous power: in fact, the whole of the spinal cord is a series of such ganglia; but this ganglion at the top of the neck is the one which is the centre of the actions which are concerned in the act of sucking. Now, this act of sucking is rather a complicated one, it involves the action of a great many muscles put into conjoint and harmonious contraction. We will say, then, that here is a nervous centre. [Dr. Carpenter made a sketch upon the black-board.] ”

“ Yes, I remember, now, it is anatomical. It's a ganglion—a nerve centre—it is what is called the zylobalsamum process."
"Well, go on; and if you come to any more of them, omit the names; they make one feel so uncomfortable." ”

“ The infra-œsophageal ganglion-mass, then, in most of the Arthropoda may be spoken of as formed by the fusion of the prosomatic or mouth-ganglia, the mesosomatic and metasomatic remaining separate and distinct. The number of ganglia which have fused may be observed by examination of the embryo, in which it is easy to see indications of the individual ganglia or neuromeres, although all such indication has disappeared in the adult; thus the {53}infra-œsophageal ganglia of the cray-fish have been shown to be constituted of six prosomatic ganglia. ”

“ In the succeeding ganglia the lobes are in general motor; the fibres composing the œsophageal commissures, and which arise from the œsophageal commissural lobes, extend not only to the subœsophageal ganglion, but pass along through the succeeding ganglia to the last pair of abdominal nerve-centres. [40] Since, then, there is a 227direct continuity in the fibres forming the two main longitudinal commissures of the nervous cord, and which originate in the brain, it seems to follow that the movements of the body are in large part directed or coördinated by the brain. ”

“ This strip, becoming gradually smaller behind, reaches nearly, though not quite, the posterior limit of the junction of the ganglia. Behind it there is, however, a region where [Pg 891] the whole dorsal surface of the ganglia is without any covering of nerve-cells.
This tongue of ganglion cells sends in, slightly behind the level of the eyes, a transverse vertical prolongation inwards into the white matter of the brain, which is shewn in the series of transverse sections in fig. ”

“ The chain of GANGLIA lying on the ventral side of the abdomen consists primitively of pairs of ganglia corresponding with the twelve segments, which are connected by longitudinal and transverse commissures. But many changes in the ganglia may be seen in insects caused by partial or entire amalgamation of single ganglia, so that in a few cases only one abdominal ganglion is present. In conclusion, a definite INTESTINAL NERVOUS SYSTEM is always present. ”

“ Fig. 241.—Section through the head of Machilis, showing the brain (br) , and subœsophageal ganglion (soe. g) ; cl, clypeus; lbr, labrum; oc, ocellus.
While the supraœsophageal ganglion, or “brain,” of the insect is much more complex than any other ganglion, consisting more exclusively both of sensory as well as motor ganglia and their nerves, it should be borne in mind that the subœsophageal ganglion also receives nerves of special sense, situated on the palpi and on the tongue, as in the bee and other insects; hence this ganglion is probably complex, consisting of sensory and motor cells. ”