ALBERT

Notes: Summary The pars tuberalis of the hypophysis of Rana temporaria presents the general structural and the cytological characteristics of an endocrine gland. It is composed of elongated cells with long, branching processes ending on the external basement membrane of the pericapillary space. The pars tuberalis cells produce secretory granules which are accumulated in the pericapillary endings of the processes. Corresponding to its separate localization, the pars tuberalis of Rana temporaria has a separate vascularization of which the efferent capillaries anastomose with the capillary plexus of the median eminence. The general direction of the blood flow of the pars tuberalis is towards the capillaries of the median eminence. Also, the secretory products of the pars tuberalis pass into the blood stream of the hypophysial portal system. Several characteristics of the pars tuberalis show that its function must be different from that of the pars distalis of the hypophysis. Moreover, in contrast with the pars distalis, the activity of the pars tuberalis is not regulated by neurohumoral factors. The results show that a role of the pars tuberalis in the regulation of the activity of the pars distalis of the hypophysis is not excluded.

Notes: Summary Electron microscopic studies and three-dimensional graphic reconstructions from serial sections have shown that the large axon terminals of synaptic glomeruli in the ventrobasal nucleus of the rat are invaginated by spine-like protrusions from the astrocyte processes surrounding the glomeruli (“micro-trophospongium”). The astrocytic protrusions are similar in dimensions and internal morphology to the synapse-bearing dendritic excrescences that also invaginate the large axon terminals. Consequently astrocytic protrusions may be overlooked, or confused with dendritic excrescences sectioned at a non-synaptic level. The intimate neuronal—neuroglial relationship at such large axon terminals may reflect ion-exchange or metabolic interactions between the astrocytes and the axon terminal.

Notes: Summary The innervation of the adrenal cortex of the rat and the pig is investigated with the electron microscope. Nerve fibers containing synaptic and two types of dense-cored vesicles come into contact with endocrine cells. There are no specialized pre- and postsynaptic membranes. The synaptic cleft is about 200 Å wide. Generally the basement membrane between nerve and cell is absent. These observations are discussed on the base of more recent experimental findings. Small fibers having an average diameter of about 0.2 to 0.5 μ and containing only tubules and filaments are considered to represent parts of an afferent nervous system.

Notes: Summary The innervation of the mesenteric microvasculature was studied in fetal and neonatal rabbits with the aid of methods demonstrating fluorescence of catecholamines and cholinesterase activity as well as a silver impregnation procedure. The results showed that: (1) adrenergic nerve fibers were present, coursing independently in the mesentery by day twenty-one of gestation, and were found routinely in the adventitia of arterioles and venules by day 25 of gestation; (2) cholinesterase positive cells and fibers of the myenteric plexus were present by day 18 of gestation but cholinergic fibers were not present in the mesentery until day 26; the latter not being associated with blood vessels; and (3) nerve fibers in the mesentery thought to be sensory stained positively with the Holmes silver method on day 18 of gestation.

Notes: Summary The sciatic nerves were analysed using light and electron microscopes in the mouse, rat, guinea pig, cat, and dog (see Methods of G. Schnepp et al., 1971). 1. In light microscopic material, the ratio “g” between mean axon diameter and mean fibre diameter increased from 0.4 for small fibres to 0.6 for the thick fibres. For a given fibre diameter the myelin sheaths in rats and dogs were the thickest, while those in mice were the thinnest. 2. The ratio “g” in electron micrographs on the other hand was constant at 0.6 over a wide range of fibre diameters. The ultrastructural values agreed with those postulated by Rushton (1951) for optimal nerve conduction. In the electron microscopic material, the myelin sheaths were the thickest in the rat. 3. A linear proportionality was confirmed to exist between internodal length and increasing fibre size. Independently of fibre size, in all sciatic nerves, a few fibres were found with internodal length of about 300 μ. 4. In electron micrographs, no species differences were observed in the structure or distribution of unmyelinated nerve fibres.

Notes: Summary Quantitative electron microscopic studies have been carried out on the human thymus. According to the equation L v =(2n)/F (Hennig, 1963) we have calculated that there is less than 0.204 mm nerve per 1 mm3 thymus tissue inside the blood-thymus-barrier (level of significance of 0.95). This result is compared to the degree of innervation in brown adipose tissue, which contains more than 160 mm nerve per 1 mm3 tissue. The biological significance of the paucity of neuronal elements in the thymus is undetermined.

Notes: Summary 1. The Harderian gland in rabbits, representing the type of a tubulo-alveolar gland, is located on the medial and posterior aspect of the eyeball and consists of two different parts, a small white lobe and a larger red one. The secretory cells in the tubular endpieces of both lobes are lipids containing cells. The lipid droplets can be stained with Sudan IV and Sudan black B. The luminal surface of both cell types is characterized by an alcianophilia at pH 2,5. 2. The tubules of both lobes have a single layer of columnar epithelium. The lipid vacuoles in the cells of the red lobe are large, these of the white lobe small. The multilocular cytoplasm of all cells contains many free ribosomes and high amounts of mitochondria lying very closely together. All cells exhibit numerous and large Golgi-zones but only few ergastoplasm membranes. 3. The lateral surfaces of the secretory cells are connected by elaborate junctional complexes (Zonulae occludentes, zonulae adhaerentes, desmosomes). These lateral surfaces are increased by intercellular canaliculi. 4. Before being released into the glandular lumen, the limiting membranes of adjacent lipid droplets fuse, thus forming a large lipid vacuole. Extrusion generally is characterized by the coalescence of the limiting membrane with the plasmalemma, the formation of an opening at the cell surface and the discharge of the secretory lipid material. In the course of another mechanism of extrusion, the fat vacuoles are transported to the apical part of the cell where consequently the plasmamembrane bulges into the lumen. Eventually the fat vacuole is pinched off surrounded by a thin cytoplasmic envelope. 5. Terminal fibers of the autonomic nervous system penetrate the basal membrane and can be found closely attached to the secretory or myoepithelial cells, partly by forming large swellings, which may be deeply embedded into the cytoplasm of the innervated cell. These terminal parts of the axons contain groups of synaptic and dense-cored vesicles, mitochondria and neurotubuli. Specific pre- and postsynaptic membranes have not been observed. The possible function of the harderian gland is discussed.

Notes: Summary Electron microscopic studies have been carried out on the innervation of the mammalian anterior pituitary and parathyroids. The total area of grid squares (2.25·10−2mm2) examined was 2000 per gland and species. In the pituitary pars distalis and in the parenchyma of the parathyroid gland we did not observe a single axon profile. According to the equation $$L_V = \frac{{2n}}{F}$$ proposed by Hennig (1963) we have calculated that there might be—if any—0.133 mm of nerves per 1 mm3 tissue in those two endocrine glands (level of significance 0.95). Comparing these results to the degree of innervation in brown adipose tissue containing more than 160 mm nerve per 1 mm3 tissue we can not imagine that such a small degree of innervation is of any biological importance. In the pituitary pars tuberalis two types of axon terminals have been found both inside and outside the basement membrane surrounding the epithelial complexes. One type contains “synaptic” and two populations of smaller dense-cored vesicles, the other one contains a population of larger granules which have some properties of the classical elementary granules. Further investigations have to clarify the functional significance of those nerve endings.

Notes: Summary Nerve fibers were demonstrated in the glycogen body of the avian lumbar spinal cord by using silver-impregnation and fluorescence microscopic (Falck-Hillarp) techniques. These nerve fibers originated from nuclear areas in lateral juxtaposition with the glycogen body. The fluorescence of the nuclear area was strongest near the polar regions of the glycogen body. It was suggested that the aminergic neurons of the avian lumbar spinal cord may influence the glycogen body. The avian glycogen body was compared with other storage sites of glycogen within the central nervous system.

Notes: Summary By means of electron microscopy “light” and “dark” pinealocytes can be distinguished in the guinea-pig pineal gland. Glial cells are rare. In the “light” pinealocyte. the most frequent cell type, some “vesicle-crowned rodlets” (VCR) show circumscribed thickenings. From these structures “vesicle-crowned balls” (VCB) have to be clearly distinguished. Furthermore “cylinders” occur, which, it is suggested, are precursors of VCB. “Dark” pinealocytes characterized by chromatin-rich nuclei and electron-dense cytoplasm are rare and contain fewer vesicles, VCR, VCB and “cylinders” than “light” pinealocytes. Numerous non-myelinated nerve fibres are situated within perivascular spaces, a few also in the parenchyma. Synapses between nerve fibres and pinealocytes were not observed. In the pineal gland of pregnant guinea-pigs the following changes can be observed in the second half of gestation. The “light” cells show many nuclear indentations and an increase of “active” zones, mitochondria, smooth ER, agranular vesicles, VCR, VCB, and “cylinders” respectively. The “dark” cells increase in number. After birth these changes reverse to normal within one week. Constant darkness leads to an activation of the “light” cells accompanied by an increase of the VCR and to an increase in number of the “dark” cells. Under constant illumination the “light” cells show a decrease of their organelles and a strong increase of the VCR. After 70 days the VCR also show a change in shape. Following reserpine treatment the VCR decrease in number and show signs of degeneration. It is discussed that the VCR function as pre- or postsynaptic structures and that they are involved either in transmitting impulses from nerve fibres to pinealocytes or from one pinealocyte to the other.

Notes: Summary Retinae from two- and three-day-old rats were explanted in plasma clots and grown in vitro with the flying coverslip method. After seven to seventeen days in culture, the retinal tissue was fixed with aldehydes and osmium tetroxide and embedded for examination with the electron microscope. Study of cross sections (perpendicular to the coverslip) revealed a histotypic pattern of organization, especially in the thicker regions of the explants. Layering of cells quite similar to that in the intact retina was seen to develop from the relatively primitive, explanted retinal epithelium. However, each layer contained fewer cells than its counterpart in vivo. All major neuronal cell types were distinguished by their location and cytological characteristics. Development of the saccules of sensory cell outer segments was observed to occur in vitro by an infolding of the plasma membrane. Synaptic ribbon complexes developed to the mature form in the outer plexiform layers, while conventional synapses were numerous in the inner plexiform layers. Synaptic ribbons were also seen in bipolar cell axons in the inner plexiform layers. Amacrine and ganglion cells in these regions were relatively sparse. A survey of posterior regions of noncultured three-day-old rat retinae showed no synapses of any sort; therefore the synapses in the cultures formed in vitro. The retina is recommended for studies of synaptogenesis in tissue culture, for it offers several advantages over expiants from other areas of the neuraxis, including a clear layering pattern, many identifiable cell processes with characteristic synaptic relationships between them, and a well-defined sequence of developmental events.

Notes: Summary This investigation is concerned with pineal organs of human embryos 60 to 150 days old. At every stage central nerve fibres enter the pineal organ by way of the habenular commissure, but are restricted to the pineal's proximal part. On about the 60th day of the development the sympathetic nervus conarii grows into the distal pole of the pineal organ from a dorso-caudal direction and plays the predominant part in the innervation of the pineal organ. After penetrating, it soon branches out and forms a network in the pineal tissue. Much later, not until the 5th embryonic month, sympathetic nerves appear accompanying the supplying vessels in the perivascular spaces. After a short time these nerves pierce the outer limiting basement membrane and penetrate the parenchyma. Towards the end of the 5th embryonic month the axons of the sympathetic nerves form varicosities containing clear and dense core vesicles. At this point large amounts of laminated granules appear primarily in cell processes, probably of pinealocytes. Isolated granules also occur in the varicosities of axons. The granules encountered here are most likely secretory granules.

Notes: Summary Nervous (sensory) pathways of the pineal complex were studied in Lampetra planeri. The following observations were made: (1) The pineal tract, containing more than 600 unmyelinated fibres, connects directly or indirectly to the posterior commissure. (2) Connections of the nervous region (NR) adjoining the parapinéal organ (“ganglion parapinéales” of Tretjakoff or “division of the left habenular ganglion” of Studnička) have been re-examined; our study shows that the rostral division of NR is connected to the parapineal organ by a short tract and to the left habenular ganglion (LHG) by a nervous layer (NL). The NR, NL, and LHG contain the same following elements: (1) A collection of typical neurones (which are rare in the NL) in an abundant meshwork of nerve fibres. (2) At least two main types of axons: (a) Type 1 axons, containing few granules (1,000–1,300 Å diameter). (b) Type 2 axons, containing numerous granules (900–2,500 Å diameter), and resembling neurosecretory axons. Type 2 axons are not observed in the pineal and parapinéal organs. (3) Axo-dendritic and axo-axonic(?) synapses. Our study concludes that NR and NL represent the rostral part of LHG; nevertheless, NR and NL may contain the parapinéal tract. The problem of possible incorporation of epithalamic elements (e.g., elements of the habenular ganglia) into the parapinéal and pineal organs in other animals has been considered phylogenetically.

Notes: Summary Umbilical vessels of guinea-pig fetuses were studied shortly before birth. In all umbilical cords investigated an innervation of the umbilical vessels is lacking. The intrafetal parts of the umbilical vessels on the other hand are richly innervated. A marked difference in the amount of nerve fibres and the pattern of innervation is found between artery and vein. The artery is supplied by a dense nerve plexus which spins around the media and which originates from nerve bundles within the outer adventitial layers. The comparatively scanty innervation of the vein exhibits a more coarsely meshed net pattern. The nerve bundles in the vein exhibit a close affinity to the vasa vasorum. Number and type of the close contacts between the muscle cells are different in the various sections of the umbilical vessels. Similar to the distribution of nerves they are almost absent in the vessels of the umbilical cord, numerously, however, in the intrafetal parts. Contrary to the innervation, the close contacts in the vein are developed more numerously and more broadly than in the corresponding artery.

Notes: Summary The vessels of the glomera that lie between the aorta and the pulmonary trunk, on the anterior and posterior wall of the pulmonary trunk, as well as the so-called glomus pulmonale of the cat have been injected with gelatine-india ink mixture. The paraganglia mentioned above are associated with the coronary circulation as chemoreceptors and are designated as the glomera coronaria. The investigations demonstrate a morphologic similarity with the glomus caroticum. Section of the vagus causes a degeneration of the synaptic structures on the glomus cells as well as changes in the cells themselves.

Notes: Summary The development of adrenergic nerves to the anterior eye segment was studied in human and guinea-pig embryos. Adrenergic terminals had already appeared in the earliest human embryos available (4–6 cm). They first appeared mainly in nerve trunks in the primitive chorioid, especially in the region of the developing ciliary body. Adrenergic nerves then grow into different structures of the eye as these develop, but typical terminals in contact with effector cells appeared late during the development, about the 25–30 cm stage. No adrenergic nerves were observed in the chamber angle. Corneal adrenergic nerves (also intraepithelial terminals) appeared much more frequently in embryos than in adults. No adrenergic neurons were observed in the retina. In the guinea-pig, the first adrenergic fibres were observed at about gestation day 35. The general principle of the development was very similar to that of the humans. At gestation day 45 to 50, the supply of adrenergic fibres was essentially that of the adult animal, except that the corneal adrenergic fibres were increasing until just before birth and that the adrenergic terminals of the chamber angle appeared shortly before term.

Notes: Summary Two neuron types are distinguished by electron microscopy in the lateral geniculate nucleus (LGN) of the monkey-a large cell (P cell) interpreted as a geniculostriate relay cell, and a small cell (I cell) interpreted as an inhibitory interneuron. The I cell, distinguished by its small size, infolded nucleus, small mitochondria, cilium and small granular bodies, forms about 10% of the total neuron population. It could not be determined whether this cell has an axon, but its dendrites, which contain aggregates of flattened vesicles, are thought to form a proportion of the “F processes”, profiles which are post-synaptic to the retinal (RLP) axons and presynaptic to the dendrites of the P cells. The small dark (RSD) axon terminals of unknown origin contact the dendrites of both cell types. After eye enucleation the P cells of the affected laminae of the LGN shrink and partially withdraw their dendrites from the neuropil. By 29 months' survival, they have only a narrow cytoplasmic rim around the nucleus. A necrotic process also occurs, affecting fine dendrites by 22 days and large profiles by 45 days, but it is not clear whether whole cells are destroyed by this process. At 45 days the I cells are commonly seen to form somatodendritic synapses. The appearance of these synapses is interpreted as the result of a withdrawal to the soma of the presynaptic dendrites. It is concluded that the I cells are probably inhibitory interneurons subject to excitation and presynaptic inhibition by the RLP and RSD axons, and a diagram is presented to demonstrate the possible significance of these connections for the transmission of information through the LGN.

Notes: Summary Light- and electron-microscopic observations were made on the alpha, beta and delta cells of the pancreatic islets of the domestic fowl and on their cytologic changes following the administration of glucose, glucagon, insulin, alloxan and carbutamide. 1. Under the light and electron microscope, two types of islets are recognized: (1) the “alpha” islet composed of alpha and delta cells and (2) the “beta” islet made up of beta and delta cells. 2. Alpha cells are large, round or columnar in shape, and contain less-developed cellular organelles and characteristic alpha granules. These dense, spherical granules are surrounded by a single smooth membrane and the matrix, with high magnification, exhibits a glomerular structure. 3. Beta cells are round, oval, or irregular in shape, and contain more or less developed cellular organelles and characteristic beta granules. These granules are polymorphic and consist of three main types; needle or bar-shaped, spherical, and ring-shaped; they are enclosed by a smooth membrane. 4. Delta cells are characterized by the presence of less dense spherical granules (diameter about 500 mμ) that are partially surrounded by an indistinct membrane. They are considered to be an independent type of cell of unknown function. 5. “Acinar-islet cells” with intermediate endocrine and exocrine morphology, are observed between the endocrine and exocrine cells along the periphery of the islets. The presence of occasional fragments of plasma membrane suggests that the cytoplasm of acinar and islet cells may intermingle. 6. The alpha cells exhibit margination of granules and release of granules by emiocytosis, in hypoglycemia induced by the administration of insulin or carbutamide. 7. After administration of glucose, glucagon or carbutamide, beta cells exhibit vacuolation and release of granules by intracytoplasmic dissolution of the specific needle- or bar-shaped granules followed by diacrine passage through the plasma membrane. On the other hand, after the administration of glucose, glucagon or carbutamide, Gomori-positive, dense, small-cored granules occur in the periphery of cytoplasm along the capillary with indications of release by emiocytosis. 8. Delta cells increase remarkably and extrude granules by emiocytosis, after the administration of glucagon, alloxan or carbutamide. 9. Administration of carbutamide stimulates the secretory activity of beta cells, as indicated by the diacrine feature of specific beta granules and the emiocytosis of small-cored granules. Carbutamide also causes an increase of immature non-granular cells in the alpha and beta islets.

Notes: Summary Electron microscopic studies of neural processes in the cerebellum, optic tectum, and cerebral hemisphere of the frog reveal a distinctive system of SER cisternae lying at intervals (commonly 1–2 μm apart) perpendicular to the long axis of axons and dendrites, interconnected by tubular, longitudinally orientated SER elements, and in direct continuity with the outer membrane of mitochondria. The transverse cisternae are fenestrated, with a single mierotubule (or rarely, two) passing through the centre of each 50–75 nm fenestration. Extensions of the SER-microtubule complex may be located parasynaptically in axon terminals and dendrites. The SER of dendritic spines also appears to be continuous with the fenestrated cisternae. Possible roles for the specialized SER (particularly of the parasynaptic extensions), such as calcium ion sequestration and ATP or monoamine oxidase transport, are discussed.

Notes: Summary The innervation of the portal vein of the white rat was examined with light-, fluorescence-, and electronmicroscopic techniques. The results are as follows: 1. Paraldehyde treated vein preparations (Falck's fluorescence method) demonstrate a predominantly longitudinally orientated external nerve plexus, being situated on the outermost muscle cells. Near the liver the nerve net is characterized by broad meshes, near the intestinal tract by narrow ones. The circular subendothelial inner plexus originates in the outer plexus of the intestinal vascular bed. 2. Nerve bundles in the fibrous adventitia were demonstrated with Gomori's Acethylcholinesterase method. In other respects, the enzyme activity was only observed in the intercellular spaces of the muscle layer. The electronmicroscopic demonstration of Acetylcholinesterase (Karnovsky's method) further showed that the enzyme activity is restricted to the muscle cell membrane. 3. The electronmicroscopic examination verified the results obtained with fluorescence microscopic techniques. a) In the proximity of the liver, only isolated nerve bundles occur on the outer muscle layer. The individual nerves are entirely surrounded by Schwann cells. Only a few of the axons in the vicinity to the muscle cell have agranular vesicles. Evaginations of the vesicular axons occur infrequently. Their distance from the muscle cell amounts to 1000–2000 Å. b) In more than one thousand thin sections, no axons were found inside the thick muscular layer. c) Subendothelial axons (inner plexus) are either partially or totally evaginated from the Schwann cells. They are densely filled with empty vesicles (350–650 Å) and contain a few dense core vesicles of 800–1600 Å in diameter. Synaptic endings were not observed. d) A dense collection of vesicle-containing axons, that were partially in their entirety and partially only from the muscle cell proximal side evaginated from the Schwann cells, were observed in the single muscle layer at the junction of the superior mesenteric and the portal vein. From these bundles, smaller bundles and individual axons pass between the muscle cells and reach the endothelium. Typical synapses were not observed. No vesiclecontaining axon was nearer than 1000 Å to the muscle cell. 4. Those axons possessing vesicles and being evaginated are considered to be vegetative conducting pathways. The excitation of the effector structures by transmitter substances is discussed in connection with the post mortem autonomic vascular contractility.

Notes: Summary 1. There is a gradual proximo-distal increase in the thickness of the muscle coat of the human ductuli efferentes, duetus epididymidis and ductus deferens. Circularly arranged smooth muscle bundles predominate in the ductuli efferentes and ductus epididymidis of the caput section. Scanty strands of longitudinally and obliquely oriented smooth muscle bundles form an additional, incomplete outer muscle layer around the ductus epididymidis of the corpus. Small smooth muscle-like cells constitute the muscle elements of the upper sections of the excretory ducts (from the ductuli efferentes to the midcauda). At the transition of the corpus and cauda epididymidis ordinary large smooth muscle cells join the small contractile cells to form—in more distal sections of the cauda—a composed, thick subepithelial muscle coat. In most distal portions of the cauda, the two-layered muscle coat of the ductus epididymidis is transformed into a three-layered coat, a pattern of construction which is retained in the vas deferens. 2. Electron microscopically, three types of contractile cells are distinguished in the human ductuli efferentes and ductus epididymidis: a) contractile cells of medium transparency containing exclusively thin myofilaments (60 Å in diameter), b) dark contractile cells containing bundles of thin myofilaments (60 Å in diameter) and single coarse filaments (140 Å in diameter), c) light contractile cells with loosely dispersed, interweaving thin and thick myofilaments. Commutual diameter changes at regular intervals are seen in individual myofilaments, giving the impression of structural periodicity not unlike that of filaments of striated muscle. Ordinary smooth muscle cells of the cauda epididymidis and vas deferens are characterized by uniformly sized, closely packed but evenly distributed thin myofilaments with numerous dense patches. 3. Fluorescence microscopy performed on formaldehyde treated freeze dried tissues reveals that the contractile cells of the ductuli efferentes in man and monkey receive a low number of single adrenergic terminal fibres penetrating the depth of the muscle coat. The adrenergic innervation of the ductus epididymidis is restricted to small peritubular nerve fascicles running contiguous to the most superficially located bundles of smooth muscle-like cells. The adrenergic ground plexus is rather wide-meshed in the proximal cauda, becomes increasingly dense in more distal cauda sections and in initial, funicular portions of the vas deferens, and reaches maximum density in abdominal parts of the ductus. Perivascular and adventitial adrenergic plexuses are well developed at arteries of the caput and corpus epididymidis in man, monkey, rabbit, guinea-pig and rat. 4. Electron microscopically, noradrenergic nerves have been identified by the presence of small granular vesicles in preterminal varicose axon dilatations. Nerve fibre swellings filled with small empty spherical vesicles have been considered to belong to “cholinergic” neurons whereas occasional varicosities equipped with some large membrane bound granules and abundant mitochondria may represent local expansions of sensory axons. 5. Neuromuscular relationships in the upper sections of excretory ducts comprise adrenergic synapses by distance (more than 1000 Å), and a few intimate, ensheated close contacts, whereas the main type of contact of nerves to ordinary smooth muscle cells in the lower duct section is by means of close but not intimate approach (500–2000 Å). 6. Adrenergic synapses in the ductus epididymidis and ductus deferens of the monkey resemble—what concerns their morphology, relationship to effectors and distribution pattern—those of man. 7. In accordance with the total number of vascular and non-vascular adrenergic nerves, visualized by fluorescence microscopy, the amount of noradrenaline varied considerably in different sections of the human male internal genital organs: The lowest amounts were estimated in the testis (0.12±0.03 μg/g). Medium to high concentrations were detected in various sections of the caput and corpus epididymidis (ductuli efferentes 0.60±0.09 μg/g; ductuli efferentes and caput 0.72±0.13 μg/g; corpus epididymidis 1.04±0.25 μg/g; proximal cauda 0.95±0.17 μg/g; distal cauda 0.97±0.19 μg/g). The highest noradrenaline content was found in the human vas deferens (prox. vas deferens 1.11±0.21 μg/g; interm. vas deferens 1.20±0.42 μg/g; distal portion 1.43±0.39 μg/g). 8. For comparison, the noradrenaline content of the testis and epididymis of the rhesus monkey, the epididymis of the rabbit and the vas deferens of the rabbit, mouse, guinea-pig and rat has been determined. 9. Adrenaline of exogenous origin was detected in the vas deferens, cauda epididymidis and plexus pampiniformis of two cases who received this catecholamine as part of the local anaesthetic drug mixture. Due to methodological reasons, the presence of small amounts of adrenaline of endogenous source in adrenergic nerves of the human and monkey internal male genital organs cannot be excluded. 10. The differences in motility behaviour of the ductus epididymidis (spontaneous, rhythmic contractions) and ductus deferens (absence of any spontaneous movements under conditions at rest) in vivo and in vitro have been correlated with the occurrence of specialized contractile cells in the upper segment (ductuli efferentes, ductus epididymidis of the caput, corpus and initial cauda) and ordinary large smooth muscle cells in the lower segment (ductus epididymidis of the distal cauda and the vas deferens) and furthermore correlated with differences in the pattern of the adrenergic innervation; the concept is advanced that progressive cytological differentiation of smooth muscle cells and the development of a dense direct adrenergic innervation suppresses autocontractility and, that the reverse condition may favour spontaneous motility of smooth muscle elements.

Notes: Summary 1. Three species of the genusGnathonemus (Gn. petersii, moorii andstanleyanus) as all species of the family Mormyridae possess two pairs of electric organs situated symmetrically on each side of the vertebral column between the caudal, dorsal and anal fins. Each organ is composed of a series of 70–170 electroplaques. 2. The stalks of the electroplaques contain no nerves. Unbranched motor nerve fibres innervate the end sections of the stalks by synaptic knobs inserting into cavities of the electroplasma. 3. The electroplasma membrane surrounds the stalk (also in the region where the stalk penetrates through holes in the body of the electroplaque) and the electroplaque. The membrane is deeply indented on the cranial side as well as on the caudal side of the electroplaque. Through this the surface is greatly enlarged. In the inside of the electroplaque are striated muscles. 4. The motor and sensory nerve fibres are clearly different in diameter. 5. The number of the nerve cells in the spinal ganglions is, in the electric organ, about a multiple larger than in the segments of the body muscular system situated in front of the electric organ. 6. The reconstruction of the peripheral sensory nerves of one segment (in view of electron microscopical analyses), reveals that these, with the exception of two free nerve endings in the integument and the free nerve endings in the dorsal myoseptum, mainly innervate four large tendons on the side of the electric organs. 7. The innervation of the electric organs leads to the hypothesis that the tendons, in connection with the function of the electric organs, possess sensory functions.