On Nerve Supply of the Suprarenal Glands of Some Animals

Abstract

The cortex of the suprarenal glands of dog and flying-squirrel, being an epitheliogenetic endocrine organ, was found devoid of fibres of cortical nerves proper. Of course the periaterial plexus send out nerve fibres which enter its parenchyma accompanying the blood capillaries, but these are extremely small in quantity and cannot be called nerves proper to the cortex. So, the greatest majority of the capillaries and cortical cells are free of nerve supply. Therefore, the mechanism occcasioning the secretion from this part may be interpreted as consisting in the seeping out of the secretory granules from the gland cells by pressure of dilation of the blood capillaries.In dog, the extracapsular connective tissue around the suprarenal gland is rich in fat tissue and contain extracapsular or suprarenal plexus with ganglia of varying size. In the rather thick capsule is formed the intracapsular plexus containing only a very few ganglion cells. In flying-squirrel, however, the capsule as well as the extracapsular tissue is very poorly developed, so that the plexuses in them are also very ill-developed. The ganalion cells in the dog's suprarenal plexus belong either to DOGIEL's Type I or to his Type II; their nerve processes are usually well developed.The suprarenal glands of these animals contain no ganglion cells in its medulla and in its cortex, unlike in the case of man. Therefore, it seems that the presence of nerve cells in the medulla has little functional significance.The nerve bundles or fibres originating in the extra- and intracapsular plexus, without sending out branches into the cortex, run through it into the medulla, so that these are the nerves proper to the latter. This medulla lies in the main in the central part of the suprarenal gland in flying-squirrel, but in dog it is otherwise found distributed in a manner suggestive of its embryological development. Medullar cell groups are found in the extra- and intracapsular spaces too, often keeping connect with the medulla at the center. Some medullar cells are found arranged cord-wise along the fibres of the medullar nerves proper running through the cortex.The medullar nerves proper are not rarely composed of thick fibres only, but usually thin fibres also come into the composition. These nerves proper, unlike those in man, run forth toward the center of the medulla, upon entering it, while sending out irregularly winding finer branches. The nerve fibres here seem to become the fewer, the smaller the animal in body size.Upon parting from the nerve bundles, the medullar nerve fibres run solitary courses as enormously thick fibres showing peculiar winding and perceptible change in size, while thick branch fibres of the same nature and besides many far thinner terminal fibres showing less change in size are sent out during the courses. These fibres of two types never end freely but always come into mutual anastomosis and form a large nervous network in the medulla. In this network, the thick fibres run peculiar looped or augular courses, so that the size and the shape of its meshes are much variegated, forming rectangles, polygones, rhomboids, ovals, spindle-forms and club-forms of varying size. Besides, quite nondescript meshes are also seen. The reticular formation by the thin fibres is also very peculiar, some very large-sized meshes appearing among the usual small-sized ones.The nerve fibres running in the medulla are not accompanied by SCHWNN's cells, because the medulla is composed of sympathetic chromaffin paraganglion cells originating in mother cells, the KOHN's so-called accessory cells, from which the sympathetic SCHWANN's cells are also derived, and thus can naturally dispense with SCHWANN's cells.The above-mentioned enormously thick fibres, besides coming into contact supply to the medullar cells, seem also to effect intracellular supply upon penetrating through these cells.