The origin, distribution, and termination pattern of nerves supplying the vertebral column and its associated structures have been studied in the human fetus by means of an acetylcholinesterase whole-mount method. The vertebral column is surrounded by ventral and dorsal nerve plexuses which are interconnected. The ventral nerve plexus consists of the nerve plexus associated with the anterior longitudinal ligament. This longitudinally oriented nerve plexus has a bilateral supply from many small branches of the sympathetic trunk, rami communicantes, and perivascular nerve plexuses of segmental arteries. In the thoracic region, the ventral nerve plexus also is connected to the nerve plexuses of costovertebral joints. The dorsal nerve plexus is made up of the nerve plexus associated with the posterior longitudinal ligament. This nerve plexus is more irregular and receives contributions only from the sinu-vertebral nerves. The sinu-vertebral nerves originate from the rami communicantes and, in the cervical region, also from the nerve plexus of the vertebral artery. Thick and thin sinu-vertebral nerves are found. Most frequently three types of thick sinu-vertebral nerves are observed, i.e., ascending, descending, or dichotomizing ones. Finally, the distribution of the branches of the ventral and dorsal nerve plexuses and of the sinu-vertebral nerves is described.

The extrinsic innervation of the abdominal organs in neonatal and adult female rats is described. Mainly an in toto acetylcholinesterase method was used; moreover, formaldehyde-induced fluorescence and acetylcholinesterase were demonstrated in sections. The major splanchnic nerve has its origin in the ninth and tenth thoracic sympathetic trunc ganglia. In the major splanchnic nerve a suprarenal ganglion is present. Sometimes the minor splanchnic nerve, arising from the tenth thoracic ganglion, joins the distal part of the suprarenal ganglion. The left and right major splanchnic nerves join the left and right celiac ganglia in the plexus. The left celiac ganglion is always bigger than the right one. The celiac plexus and the celiac inferior mesenteric plexus are joined by the intermesenteric plexus. Para-aortic nerves, originating in the caudal part of the thoracic sympathetic truncs, also join the abdominal prevertebral plexuses. The lumbar splanchnic nerves, not symmetrical in their origin, join the prevertebral plexuses and give off branches to the abdominal organs. The suprarenal glands receive bundles of nerve fibers, sometimes ganglionated, from the suprarenal ganglion. The kidneys are innervated from the celiac plexus, the upper lumbar splanchnic nerves and the intermesenteric plexus. The ovarian nerves are derived from the celiac plexus, the intermesenteric plexus and the upper lumbar splanchnic nerves. Bundles of nerve fibers run from the suprarenal ganglion in the celiac plexus in the direction of the suspensory ligament of the ovary. In many respects this description is at variance with existing literature on the autonomic innervation in the rat. These differences with the standard literature are relevant to those workers engaged in experiments on the sympathetic innervation of abdominal viscera.

The nerves supplying the spinal dura mater were studied in four human foetuses (16-22 weeks) with the acetylcholinesterase in toto staining method. The ventral spinal dura contains a dense, longitudinally oriented, nerve plexus, which receives its contributions from: (I) the sinuvertebral nerves, (II) the nerve plexus of the posterior longitudinal ligament, (III) the nerve plexus of radicular branches of segmental arteries. Dorsal dural nerves are much smaller in number, do not form an evident plexus and do not reach the medial region of the dorsal dura. The dorsal nerves are derived from the ventral dural plexus at the level of the "intersleeval" parts of the dura mater. The ventral dural nerves may extend up to eight segments, with a great amount of overlap between adjacent nerves. This may provide an anatomical substrate for the understanding of extrasegmentally referred dural pain. The curled bundles of nerve fibres of pathways (I) and (II) provide an adequate adaptation to displacements of the spinal dura mater during flexion and extension. Pathway (III) has not been described before. The described nerve plexuses may be of importance in elucidating the mechanisms of epidural therapies in back pain and peripheral vascular disease.

The extrinsic innervation of the pelvic organs in neonatal and adult female rats is described. Mainly an in toto acetylcholinesterase method is used; moreover, acetyl-cholinesterase is demonstrated in sections. The hypogastric plexus is defined as the nerve plexuses caudal to the inferior mesenteric ganglia comprising the uterine cervical ganglia and various smaller ganglia. The origin of the hypogastric plexus is formed by the hypogastric nerves, bundles of nerve fibers from the lumbar and cranial part of the sacral sympathetic trunks, bundles of nerve fibers from the inferior mesenteric ganglia and the pelvic nerves. The origin of the caudal part of the hypogastric plexus is also constituted by the pudendal nerves. The uterine nerves are derived from the ovarian nerves, the uterine cervical ganglia, the hypogastric nerves and the lumbar sympathetic trunks. The nerves to the urinary bladder are derived from the ganglionated nerve plexuses in the mesometrium as well as from the uterine cervical ganglia. The vaginal nerves are derived from the uterine cervical ganglia, the ganglionated nerve plexus in the mesometrium and the pudendal nerve. The rectal nerves are derived from the ganglionated inferior mesenteric plexus, the uterine cervical ganglia and the pudendal nerves. The hypogastric plexus in the rat is in many respects more complex than is known from the literature. These anatomical data are relevant for instance to experimentators who use the pelvic autonomic plexuses in the rat as a model system for the analysis of autonomic neuronal regulation systems in mammals.

The segmental organization of the thoracic sympathetic trunk and all its ramifications was studied in 6 human fetuses (16-22 weeks) by means of the acetylcholinesterase in toto staining method. Each trunk was divided into 12 sympathetic segments. A segment is defined as that part of the sympathetic trunk which is connected via its rami communicantes with one spinal nerve, without discriminating between grey and white rami. The diameter of the rami communicantes and their direction towards the spinal nerves are variable. The number of peripheral segmental ramifications of the trunk is much larger than assumed previously. Each thoracic sympathetic segment gives off at least 4-5 nerves. Three categories of nerves are discerned: (1) large splanchnic rootlets confined to the greater, lesser and least thoracic splanchnic nerves, (2) medium-sized splanchnic nerves directed towards thoracic viscera, some of which give off branches towards costovertebral joint plexuses and, described for the first time in man, (3) small nerves which ramify extensively and form nerve plexuses in the capsule of the costovertebral joints. The majority of the ramifications is formed by the nerves of the third category. The existence of Kuntz's nerve, connecting the 2nd intercostal nerve and 1st thoracic spinal nerve, is confirmed in four specimens. The nerve plexuses of the costovertebral joints receive a segmentally organized innervation: they receive their input from the neighbouring sympathetic segment and the one cranial to it. It is concluded that the thoracic sympathetic branches in man show a complex, segmentally organized pattern and may have a considerable component of somatosensory nerve fibers. The complex relationships must be taken into account in surgical sympathectomies.