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Electron microscopy of superior cervical ganglia of the mouse shows both pre- and postganglionic elements impinging upon the soma of principal neurons. The preganglionic cholinergic axon terminals are estimated to cover about 0.7% of the total surface area of the neuronal soma and are characterized by dense packing of synaptic vesicles which remain unchanged after the administration of 5-hydroxydopamine. Postganglionic elements are estimated to cover about 1.8% of the total surface of the neuronal soma. In many cases they contain small granular vesicles (with or without agranular reticulum), and are considered to be represented in part by vesiculated segments of the dendrite and in part by recurrent axon collaterals of the principal neuron. These postganglionic elements usually make puncta adhaerentes, but occasionally an efferent synapse, on the soma of principal neurons in the ganglion. Evidence is presented which suggests that the soma, in turn, is capable of influencing the perisomal, postganglionic elements through a somatic efferent synapse.

An ultrastructural study has been made of the suprasylvian gyrus of the cat after its complete surgical isolation. In acute experiments (36 to 48 hours after isolation) the distribution and type of degenerative changes in axons and axon terminals belonging to extra-gyral fibers have been studied. The number of dark degenerating boutons nerver reaches 15% of the synaptic population. Such boutons are scattered throughout all cortical layers, but they are more numerous in the superficial than in the deeper layers. The majority of the dark degenerating boutons establish synaptic contact on dendritic spines, less frequently they synapse on dendritic shafts, and only rarely on neuronal perikarya. In some instances the degeneratin presynaptic boutons and their postsynaptic spines seem to follow a simultaneous degenerative process, as they are apparently entrapped in the same astrocytic cytoplasm. Nevertheless, free postsynaptic spines, bearing normal-looking postsynaptic densities are occasionally observed in the neuropil of the acutely isolated cortex, as well as in subacute (13 days after isolation) and chronic (30 to 46 days after isolation) animals. In the chronically isolated gyrus, except for the intense, diffuse gliosis, the presence of numerous dark, degenerating, small myelinated fibers and the persistence of some degenerating boutons, the nervous parenchyma seems, from a qualitative assessment, to have a normal appearance. A quantitative coparison of the various kinds of synapses in the unoperated suprasylvian gyrus and in the chronically isolated gyrus, has been carried out, since this is the only way to study the final result of deafferentation on the synaptic arrangement in the isolated cortex. The number of axon terminals is decreased by 20 to 30% in the chronic preparation. This diminution of synapses is more marked in the superficial than in the deeper layers: thus, the index of synapses in superficial layers is one synapse/10/μm2 in control animals, and decreases to one synapse/17/μm2 in chronic animals. However, in the deeper layers it is one synapse/13/μm2 in control animals and only decreases to one synapse/16/μm2 in chronic animals. The large majority of the lost boutons formerly synapsed on dendritic spines. In addition to the loss of synapses and to the intense gliosis, other morphological alterations were observed: reduction in the size of all cortical neuronal perikarya, modification of some vascular beds with dilatation of the Virchow's spaces, and spread of the basal membranes for long distances from the capillaries. A number of pathological features are encountered in the chronically isolated suprasylvian gyrus: (1) loss of afferent fibers, (2) loss of dendritic spines, (3) neuronal atrophy, (4) intense marginal and interstitial gliosis, and (5) alterations of some perivascular spaces; the last feature may give a morphological explanation for the particular electrophysiology observed in this type of cortex; since it may give rise to alterations in the permeability of the vascular barrier, resulting in chemical modifications of the interstitial milieu which may be the cause of the altered neuronal activity.

The synaptic organization throughout the nucleus gracilis has been investigated in unoperated cats. Axon terminals of variable size can establish synaptic contacts with neuronal somata, dendritic processes, initial segment of axons or with other axon terminals at “complex synaptic arrangements.” Large boutons with rounded vesicles are regularly associated with smaller boutons containing flattened vesicles; the latter type of bouton forms frequently a double synapse being presynaptic to the large bouton and to the element postsynaptic to this (“complex synaptic arrangements”). Medium-sized to small axon terminals of the “isolated” type contain primarily either rounded or flattened vesicles. These boutons are surrounded by a thin glial process which also wraps the postsynaptic element, mostly represented by a small dendritic profile. The “isolated” type of bouton seems to be more abundant in the rostral than in the caudal part of the nucleus. In all unoperated control animals altered axons and axon terminals are present. They are enlarged and display hyperplasia and dilatation of tubular profiles of smooth endoplasmic reticulum as well as proliferation of microtubules and various aspects of mitochondrial degeneration. In cats sacrificed 48 hours after section of lumbo-sacral dorsal roots a high number of “dark” boutons are observed in various stages of degeneration. These terminals are identifiable with the large boutons containing rounded vesicles and postsynaptic to the smaller boutons with flattened vesicles. The morphology of dorsal root terminals in the nucleus gracilis is discussed in relation to that of primary afferent terminals in other central structures and to the functional aspects of axo-axonic contacts. The sensori-motor cortex was removed in another series of animals which were sacrificed after one to four days. As a consequence of such lesions cortical fiber terminals in the nucleus gracilis may undergo either the “dark” or the “light” type of degeneration. These terminals are of smaller size than those of primary afferents, they usually synapse on dendritic profiles of small diameter, are not involved in axo-axonic contacts and seem to contain rounded vesicles. Therefore they can be identified with at least some of the small and medium-sized boutons of the “isolated” type.

A general account is given of synaptic organization in the rat LGd, with special emphasis on the intrinsic neurons, and the vesicle-containing P-boutons to which they give rise. The account is based on ultrastructural studies of normal adult rats, and of experimental animals surviving from less than one day to more than four weeks following unilateral eye removal or ablation of the visual and peri-visual cortex. P-boutons originate as narrow stalks or as blunt outpushings from presynaptic dendritic shafts. Commonly a single appendage comprises a series of P-boutons interconnected by narrow intervaricose portions. There is a very close correspondence in size and appearance between such appendages characterized by electron microscopy and the complex dendritic appendages seen in Golgi impregnations. P-boutons represent the principal synaptic territory of the intrinsic neuron. They arepresynaptic to relay cell dendrites (or dendritic appendages), and to other P-boutons (or, less commonly, to presynaptic dendrites). They arepostsynaptic to other P-boutons (or, less commonly, to presynaptic dendrites), to axon terminals containing ‘flattened’ vesicles (F-boutons), and to large intraglomerular axon terminals containing spherical synaptic vesicles (R-boutons). Degeneration of R-boutons after enucleation indicates that most are the terminals of retinal afferents. The P-boutons are intermediate elements in various serial synapses, the most characteristic of which is the intraglomerular triplet (or triad) synapse. At triplet synapses, a P-bouton and a relay cell dendrite onto which the P-bouton synapses, both receive at least one synaptic contact from an R-bouton. The possible role of triplet synapses in rapid feed-forward inhibition is considered. P-boutons and presynaptic dendrites also establish reciprocal synaptic relationship with one another, although closely spaced reciprocal synapses (c. 0.25 μm apart) are rare. The F-bouton population originates at least in part from small myelinated axons. The F-boutons contain closely packed, cylindrical synaptic vesicles, establish Gray type 2 contacts and are never postsynaptic. They are greatly outnumbered by P-boutons within the glomeruli, but synapse extensively in the extraglomerular neuropil onto both intrinsic and relay cell somas and dendrites, and onto the initial axons of relay cells. The possibility that some F-boutons originate from brain stem afferents is considered.

Gas flow analysis, autoradiography, and electron microscopy were performed on radial nerve cords of sea stars injected intragastrically with [14C] leucine tracer, a precursor of axonal proteins. Neurotubules, neurofilaments, and axonal transport were demonstrated for the first time in sea stars. This transport occurred at two rates (fast phase: 240–480 mm/da, slow phase: 20–40 mm/da) moving in both the cellulifugal and centripetal directions. The rate in the centripetal direction was slightly slower. Displacement of peaks of radioactivity appeared cyclic.Transneuronal transport apparently occurred between several groups of neurones suggesting the possibility of metabolic communication, perhaps across the synapse, between groups of neurones or even areas of the nervous system. Regenerating nerve cords demonstrated an increase in the rate (400–600 mm/da) and quantity (6–11 times as much) of label transported to cord termini.

Synapse development was studied by electron microscopy in the molecular layer of the dentate gyrus of the rat at 4 different ages: 4, 11, 25, and at least 90 days after birth. At 4 days after birth, less than 1% of the synapses seen in the adult are present. Even by 11 days the total number of synapses is still less than 5% of those in the molecular layer of the adult. Synaptogenesis is most active between 4 and 11 days when the total number of synapses approximately doubles every day. Between 4 days and adult the total number of synapses increases by nearly 100-fold in the dendate gyrus.

The three dorsal ocelli of worker honeybees have been studied by light and electron microscopy. Each ocellus has a single flattened spheroidal lens and about 800 elongated retinular cells. Retinular cells are paired and form a two-part plate-like rhabdom between their distal processes. Each rhabdomere comprises parallel microvilli projecting laterally from the apposed retinular cells. Primary receptor cell axons synapse within the ocellus with ocellar nerve fibers of two different calibers. Each ocellus has eight thick fibers ca 10 mm in diameter and several thinner ones less than 3 mm in diameter. Fine structural evidence suggests that retinular axons end presynaptically on both types of ocellar nerve fibers. Since all retinular cells apparently synapse repeatedly with the thick fibers this involves a convergence of about 100:1. Thick fibers always terminate postsynaptically within the ocellus while thin fibers terminate presynaptically on other thin fibers, thick fibers or retinular axons. Structural evidence for synaptic polarization indicates that retinular cells and thick fibers are afferent, thin fibers efferent. Thus complex processing of the ocellar visual input can occur before the secondary neurons of the three ocelli converge to form the single short ocellar nerve which runs to the posterior forebrain.

Scanning and transmission electron microscopy of the capsule and adjacent tissues of the eye of Helix aspersa revealed strands of tissue interconnecting tentacular wall and optic capsule. These strands are composed of collagen, glial and muscle cells, and bundles of axons. After entering the capsule, the axons synapse with the muscle cells in the capsule. The structure of the capsule and capsular strands is similar to that of the tentacular wall. Tentacle, capsule, and capsular strands appear to be innervated by axons of common origin. The functional significance of the neural pathway here described is discussed.

Publisher Summary This chapter describes the behavioral pharmacology of d -amphetamine. Food deprivation and amphetamine are both known to increase behavioral arousal in the rat. Amphetamine is generally believed to induce psychomotor excitation by increasing the synaptic release of catecholamines, and by blocking their reuptake from the synapse. The importance of this factor in the potentiation of amphetamine stimulation after chronic reserpine treatment has been evaluated. Groups of rats given chronic reserpine treatment showed significantly increased spontaneous locomotor activity, and an enhanced response to d -amphetamine as compared with controls. It is noteworthy, that the chronic reserpine treatment produced variable effects on final body weight, and the increased spontaneous activity, and the enhanced responsiveness to amphetamine were observed only in those individual animals which suffered marked weight loss. The food intake of the control group was restricted so that it was similar to the ad libitum intake of the rats treated with reserpine. In this case, where both the saline and the reserpine-treated groups suffered similar weight losses over 10 days, the chronic reserpine group was in no sense more responsive to amphetamine than were the controls.

The retinula cell axons entering the synaptic region of the optic lamina in the crayfish form large expanded bag-like terminals which are organized with other neural elements into structural units called ‘cartridges’. The cytoplasm of the terminals contains synaptic and coated vesicles, ER cisternae, clusters of tubular elements, and mitochondria. Several mitochondria are often found associated with a single large rod-shaped inclusion present within each terminal. The rod-like formation could be demonstrated in both light and EM material, it is composed of 85–95 A filaments and averages I μm in width and 6.5 μm in length. The terminal synaptic contacts are characterized by a bar-shaped presynaptic density and three postsynaptic elements. Some synaptic vesicles appear aligned along the bar density which measures approximately 800 A in width and 0.75 μm in length. Each terminal synapse has three postsynaptic elements which have an electron-dense fringe along their membrane bordering the synaptic cleft. From the planes of section through this contact a composite reconstruction is presented. Also present along the central border of the terminals are numerous small invaginated processes, some of which extend almost to the middle of the terminal. No membrane specializations were found along these processes and they have been tentatively identified as neuronal.

The synapse-bearing nerve terminals of the opener muscle of the crayfish Procambarus were reconstructed using electron micrographs of regions which had been serially sectioned. The branching patterns of the terminals of excitatory and inhibitory axons and the locations and sizes of neuromuscular and axo-axonal synapses were studied. Excitatory and inhibitory synapses could be distinguished not only on the basis of differences in synaptic vesicles, but also by a difference in density of pre- and postsynaptic membranes. Synapses of both axons usually had one or more sharply localized presynaptic "dense bodies" around which synaptic vesicles appeared to cluster. Some synapses did not have the dense bodies. These structures may be involved in the physiological activity of the synapse. Excitatory axon terminals had more synapses, and a larger percentage of terminal surface area devoted to synaptic contacts, than inhibitory axon terminals. However, the largest synapses of the inhibitory axon exceeded in surface area those of the excitatory axon. Both axons had many side branches coming from the main terminal; often, the side branches were joined to the main terminal by narrow necks. A greater percentage of surface area was devoted to synapses in side branches than in the main terminal. Only a small fraction of total surface area was devoted to axo-axonal synapses, but these were often located at narrow necks or constrictions of the excitatory axon. This arrangement would result in effective blockage of spike invasion of regions of the terminal distal to the synapse, and would allow relatively few synapses to exert a powerful effect on transmitter release from the excitatory axon. A hypothesis to account for the development of the neuromuscular apparatus is presented, in which it is suggested that production of new synapses is more important than enlargement of old ones as a mechanism for allowing the axon to adjust transmitter output to the functional needs of the muscle.

An electron microscopic study of the retina of the albino rat, with particular emphasis on the synaptic organization of the inner and outer plexiform layers, has been correlated with specimens impregnated with a modified Golgi technique. The central element of the photoreceptor “triad” in the outer plexiform layer is a bipolar cell dendrite. Two types of synaptic contacts were observed in the inner plexiform layer, the “dyad” ribbon synapse and the conventional synapse. The postsynaptic elements of the “dyad” consisted of an amacrine process and a ganglion cell dendrite. Conventional synapses were made by amacrine processes which were usually presynaptic to bipolar terminals. Reciprocal synapses between processes making ribbon synapses and those making conventional synapses were seen. Golgi technique revealed the presence of two types of bipolar cells, three types of amacrine cells, and one type each of horizontal and ganglion cell. These findings are discussed in relation to reported receptive field organization.

Summary (1) A diphasic response consisting of a negative-, followed by a positive-going dorsal root potential (DRP) was evoked in L6 or L7 dorsal rootlets of unanesthetized spinal cats by 10 times group I threshold stimulation of the gastrocnemius-soleus muscle nerve. (2) The administration of 2.5 mg/kg bicuculine reversibly abolished, within 30 sec, first the negative and then the positive DRP. The time course for the recovery of the negative DRP was longer than that of the positive DRP. (3) Smaller doses of bicuculline (0.2–1.0 mg/kg) were usually much more effective against the negative than the positive DRP in terms of both magnitude and duration of suppression. (4) A selective action against the negative DRP was also observed, but with less consistency, after picrotoxin (3.0 mg/kg) administration. (5) Semicarbazide (200 mg/kg) induced a gradual diminution and often abolition of both DRPs over the course of 3 h. A selective reduction of the negative DRP occured after 60 min. (6) Suppression of the positive DRP by agents which block the receptor attachment (bicuculline and picrotoxin) and synthesis (semicarbazide) of GABA suggests that GABA is a transmitter in the pathway(s) mediating primary afferent hyperpolarization. (7) The possibility that GABA synapses occur in each of two separate pathways leading to the afferent terminal is discussed. According to this model, the positive DRP represents the GABA-mediated inhibition of a tonic non-GABA-mediated PAD; the negative DRP is conducted through a separate pathway terminating in a GABA-mediated axo-axonic synapse. The differential susceptibility would reflect, according to this model, anatomical or physiological differences between the GABA synapses of the respective pathways.

Summary Two nerves arise from the subpedunculate lobe of the octopus brain. (1) The subpedunculate nerve, ending with neurosecretory terminals at the pharyngo-ophtalmic vein. It appears to be involved in growth and/or maturation. (2) The optic gland nerve, ending in the optic gland. Two types of synapses are found in the inactive optic gland (axo-axonal and axo-glandular); only one of them in the active gland (axo-glandular). The axo-axonal synapse is supposed to inhibit the axo-gladular synapse in immature glands.

In freeze-fractured frog sartorius muscles, the long terminal branches of motor axons possess a series of narrow transverse ridges on their surface, bordered by rows of relatively large particles within the presynaptic membrane. By their exclusive location opposite muscle folds, it is apparent that these ridges represent anen face view of the electron-dense cytoplasmic bands around which synaptic vesicles cluster. In resting terminals there is no sign that vesicles underlie these ridges, except for an occasional bulge where a vesicle presses against the plasmalemma; but in terminals stimulated briefly in fixative, the ridges are surrounded by a number of small dimples where synaptic vesicles attach to the plasmalemma. Such ‘vesicle sites’ do not appear when Mg++ is used to prevent the transmitter release that results from stimulation, so they presumably represent sites of transmitter discharge. However, more vesicle sites appear in terminals stimulated in more slowly acting fixatives, so they appear to accumulate for some time during fixation and do not indicate the instantaneous level of transmitter release. Vesicle sites occur in a variety of sizes and shapes that may represent different stages of vesicle discharge. Dimples which appear during stimulation under Schwann processes, where endocytosis of coated vesicles has been found to occur, are sometimes larger than vesicle sites but otherwise look much the same; so it is not possible to readily distinguish between the freeze fracture images of synaptic vesicle discharge and coated vesicle formation at this synapse. The muscle membrane beneath nerve terminals is paved with clusters of relatively large particles which mostly appear on the cytoplasmic half of the membrane after fracture. These clusters of particles occur in regions of the postsynaptic membrane that are coated by plaques of electron-dense cytoplasmic fuzz. Immediately around the clusters are a number of tightly-packed, orthogonal aggregates of slightly smaller particles.

The distribution of aminergic and non-aminergic nerve fibres to the different constituents of the wall of the digestive tract in various regions is described. Aminergic fibres synapse with all nervous perikarya. Densely interlacing networks of nerve fibres are found in both layers of the tunica muscularis and in the lamina muscularis mucosae. A finely meshed plexus is observed in relation to the wall of the blood vessels in the wall of the gut. There are many fibres connecting the muscular and the vascular plexus. No nerve fibres have been observed in direct relation to the epithelium.

The theoretical properties of synapses such as those in the retina which operate on graded potentials are developed using work on tetrodotoxin-treated synapses as a basis. A linearized model of a two-synapse negative feedback loop analogous to the bipolaramacrine feedback loop in the retina possesses a frequency response which developes an increasingly prominent resonance peak at higher input levels and under some circumstances shows instability. Psychophysical studies have shown that the visual system also exhibits this behaviour suggestive of progressive underdamping in a harmonic oscillator. Evidence in favor of the hypothesis that resonance originates in the loop is presented, the conclusions being that the loop functions to tune the retina to a range of temporal frequencies.

The sacculus, the hearing organ, of the goldfish was fixed with three different kinds of fixatives: osmium tetroxide, glutaraldehyde and formaldehyde. Three kinds of synapses are encountered in the sensory epithelium: the synapse between the hair cell and the afferent nerve ending, the synapse between the efferent nerve ending and the hair cell, and the synapse between the hair cell and the afferent nerve ending, there are synaptic vesicles about 370-430 A in average diameter in the hair cell side of the junction. The vesicles are always round in dependent of the fixative used. In the other two kinds of synapses, the efferent ending contains smaller vesicles about 310-360 A in average diameter. The shape of the vesicles changes according to the fixative used; round in osmium tetroxide-fixed materials, and elongated in aldehydefixed materials. The synapse between the hair cell and the afferent nerve ending in excitatory in nature, while the other two types of synapses are thought to be inhibitory in nature.

The migration of granule cells and the maturation of the various elements of the granular layer were studied in the cerebellar cortex of rats aged 0, 3, 5, 7, 10, 12, 15, 21 and 30 days with histological, histochemical, autoradiographic and electron microscopic techniques. The bulk of the granule cells are formed during the second week, but due to the time required for their migration and the lag in the formation of dendrites, few glomerular synapses are formed with mossy fibers before the beginning of the third week and the process is still in progress at 30 days, long after the dissolution of the external germinal layer. The maturation of Golgi cells is a protracted process. Their axons synapse with granule cell dendrites as soon as the glomeruli begin to mature. Evidence was obtained that mossy fibers synapse with the dendrites of Golgi cells. Towards the end of the second week the Lugaro cells are formed and synapses appear on their somata during the third week. Among these synapses the recurrent collaterals of Purkinje cell axons were identified. The Lugaro cells may be the primary targets of the infra and supraganglionic plexuses formed by these collaterals. In conclusion it was suggested that there are three major, successive stages in the neurogenesis of the cerebellar cortex, the morphogenic, synaptogenic and gliogenic. However, in the large Purkinje cell the synaptic maturation of one region (the soma) may begin before the morphogenic and synaptogenic maturation of the entire cell (the dendrites) is completed.

The behaviour of neurones during signal transmission is determined partly by the input to the nerve cell and partly by its inherent properties. A detailed knowledge of the spike trains, which are input to and output from a synapse, may yield information about these synaptic mechanisms. This problem has been treated in relation to data from the dorsal spino-cerebellar tract (DSCT) cells monosynaptically activated from primary endings of muscle spindles. After a description of the firing pattern of these cells the behaviour of various models are examined by computer simulation. A particular type of model approximates the behaviour of the DSCT neurones closely with a rather narrow set of parameters. The model predicts that about 15 primary afferent fibres from one muscle converge on one DSCT cell and that the average size of their EPSPs may be as large as 50% of the threshold of firing.

The effects of motor-nerve section on neuromuscular transmission in the locust extensor tibiae preparation have been investigated by intracellular recording. Impulse transmission failed between the ninth and twenty-fourth post-operative days, in the region of the nerve-muscle synapse. Before impulse transmission failed, abnormally large depolarizing and hyperpolarizing responses to stimulation of the ‘slow’ axons, and prolonged depolarizing responses to the ‘fast’ axon were recorded from many muscle fibres. At the time of impulse transmission failure the discharge of spontaneous miniature post-synaptic potentials underwent a number of complicated changes leading to the appearance of ‘giant’ miniature potentials up to 10 mV in height. The discharge persisted apparently for a few days after the muscle became neurally inexcitable. When the discharge finally stopped the fibres became permanently electrically silent; no evidence was obtained for a resumption of miniature activity during the later post-operative days. The cessation of the miniature discharge is apparently correlated to the decline of muscle-resting potential observed in denervated insect muscle and the possibility that the transmitter, or a substance released along with it, maintains the resting potential of the muscle at its normal level is discussed.

1. Degeneration of synapses in the cat superior cervical ganglion after division of preganglionic fibers was expressed under the optical microscope by argyrophilia or argyrophobia, hypertrophy, and lysis. Under the electron microscope, two types of changes were observed during this process (“dark” and “light” degeneration of synapses). 2. The structure of the synaptic endings in sections impregnated with silver remains similar at all stages of regeneration, although their function undergoes considerable change during this period. Electron-microscopy showed that transmission of impulses through regenerating synapses is restored only after numerous synaptic vesicles have appeared in their presynaptic parts, and active zones of pre- and postsynaptic membranes have been formed. 3. Formation of the presynaptic part of the synapse precedes specific differentiation of the postsynaptic membrane. The symmetrical type of structure of the primary contact observed in early stages of regeneration of axonal endings is replaced by formations which are indistinguishable in structure and function from ordinary synapses.

The synaptic contacts made by carp retinal neurons were studied with electron microscopic techniques. Three kinds of contacts are described: (1) a conventional synapse in which an accumulation of agranular vesicles is found on the presynaptic side along with membrane densification of both pre- and postsynaptic elements; (2) a ribbon synapse in which a presynaptic ribbon surrounded by a halo of agranular vesicles faces two postsynaptic elements; and (3) close apposition of plasma membranes without any vesicle accumulation or membrane densification.

Consciousness is objectively described as psychonic energy, necessarily generated at every synapse in the central nervous system upon passage of impulses from neuron to neuron. The connective, or junctional tissue at the synapses capable of giving rise to psychonic energy, is termed, at any individual synapse, a psychon. There are two types of cell structure and two types of general synaptic arrangement, that at the sensory psychons being sensation, the motor psychons motation. There has been much confusion between the statements that emotion is sensation and that the awareness of a reaction occurring is emotion. Physiologists, in disproving the sensory-content statement of James' theory, conclude that emotion consists of a distinctive pattern of neurons in the central nervous system, excited to activity by initial response to the stimulus. Application of the physiologists' conclusion to James' original formulation of his theory can be made with perfect harmony if motation be accepted as a basic unit of consciousness on equal terms with sensation. Emotions might be defined quite simply as composed of designated groups of motations, characteristically combined. Pleasantness might be defined as alliance of simple motations, and unpleasantness as conflict of simple motations. (PsycINFO Database Record (c) 2006 APA, all rights reserved)

IN spite of phylogenetic differences, the vertebrate (frog) myoneural junction and the giant synapse in the squid stellate ganglion have similar characteristics of transmitter release1–8. In this article I report quantitative data on this similarity, on the roles of Ca2+ and Mg2+, and the dependence on temperature.

Fluorescence and electron microscopy of the turtle heart indicates the presence of monoamine-containing, granulated cells in the wall of venous sinus and near the openings of the aortic trunks. These cells occur in clusters and are always in association with nerve fibers and/or ganglion cells within the turtle heart. Vesiculated axon terminals make a synaptic contact with the cytolemma of the granulated cell which in turn makes a synapse to the processes from the other granulated cell and to the cardiac nerve fibers. The close contact occurs also between the granulated cell process and the smooth muscle cell membrane in the wall of large vessels. The granulated cell has no special relationship to the blood capillaries. The significance of these results is discussed in relation to nervous control of the cardiac activity of the turtle.