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Carnosine (β-alanyl- l -histidine) is present in the olfactory bulb and olfactory epithelium of mice and rats at 1–2 nmole/mg tissue. Peripheral deafferentation or central denervation causes a rapid, selective decrease of this dipeptide from the reciprocal portion of the primary olfactory pathway. These data demonstrate the localization of carnosine within the primary olfactory chemoreceptor neurons and suggest a possible role for this compound in neural transmission.

New results as revealed by scanning and transmission electron microscopy have given us further knowledge about the structure of the olfactory region of vertebrates. With comparative studies we are now able to discuss the functional relationship of this region. In all vertebrates the olfactory cell is a primary sensory cell. The apical segment of the olfactory cell with its olfactory vesicle is involved in the formation of the olfactory border. As a rule the receptor possesses cilia or cilia-like processes. These are absent in the olfactory receptor of the shark, the microvillus receptor of the fish and the olfactory cell of Jabonsons organ of amphibians, reptiles and mammals. The odorous substances in the fish are brought to the receptor membrane by the water flow. In air breathing vertebrates a terminal film is present. This film is a product of secretion from the Bowmans glands. Gasous odorous substances must first be dissolved in the terminal film and penetrate it before reaching the receptor membrane. The cilia-like olfactory process of the fish in the proximal segment is not essentially different from the kinocilia of the supporting cell, except that they are shorter. In contrast the olfactory cell of air-breathing vertebrates form cilia-like processes with a short cilia-like proximal segment and a long and very thin distal end piece. In the amphibians and sauropsidians the end pieces can have a lenght of up to 150 μ and up to 80 μ in mammals. The olfactory vesicles with its processes undergo continuous regeneration. The olfactory epithelium of man show the same structural formation as observed in other mammals. Regressive changes in the adult can lead to a reduction in the number of sensory cells and also to a flattening of the epithelium. Morphological criteria for regenerative processes in the sensory cell structures are present. A specialized olfactory cell type has been found in some teleosts. This cell is characterized by a small pit below the olfactory border in which the cilia of the olfactory cell are redrawn. There is some evidence that this olfactory cell type may be compared with the olfactory cells in the parafollicular tubes of lamprey. The so called rod-shaped receptor in the olfactory mucosa of fishes has no axon and is therefore no olfactory cell. The same kind of cell is also present in the olfactory mucosa of airbreathing animals. We classify this cell as brush cell. Comparative electron microscopic studies reveal identical ultrastructural organization of the olfactory bulb in all classes of vertebrates, including cyclostomes and man. The size and structure of synapses in the olfactory bulb are specific for each connection type. The dark endings of the olfactory receptor cells have small axo-dendritic contacts to the bright mitral or tufted cell processes within the glomeruli. Granule cells, periglomerular cells and mitral cells interact by dendro-dendritic, dendro-axonic and somato-dendritic synaptic complexes which often have “reciprocal” arrangements. Presynaptic endings on the granule cell dendrites and somata contain a large number of small synaptic vesicles and have membrane complexes more than 0.5 μm in diameter. In the periventricular or central zone of the olfactory bulb excitatory synapses with interdigitation between the pre- and postsynaptic processes are present. We are able to give schematic representations of postulated nerve circuits with the aid of the different morphological appearances of the different synapses. The cellular composition of the taste buds of different mammals can be described from electron microscopical studies. As a rule 5 cell types which regenerate through mitosis from the basal or marginal cells can be differentiated. Only the active sensory cell forms synaptic membrane complexes. It sends rod-shaped processes into the taste pores. Growing and dying sensory cells do not possess these processes. The supporting cells surround the single sensory cell. The apical pole of the supporting cell enters the taste pore by a bundle of microvilli. Secretory granules accumulate in the apical part of the supporting cell and empty their contents into the taste pore. The terminal processes of the myelinated afferent nerve fibres form a plexus in the lamina propria and penetrate the taste bud with numerous itraepithelial branchings.

1. Electrophysiological study disclosed that chloroform and some other odours generate long-lasting positive potentials in the olfactory epithelium of the bullfrog, while electron microscopical study showed that they elicit vigorous protrusion of the distal cytoplasmic portion of the supporting cell containing the secretory granules.2. The secretory process of the supporting cell is as follows: The first detectable indication is the protrusion of the apical portion of the supporting cell (Pls. 3 and 4); the protruded part detaches from its maternal supporting cell (Pl. 7 B), floats as a droplet in the mucus (Pl. 5), and finally the secretory granules inside the droplet disintegrate into the mucus (Pls. 6 and 7 A).3. The secretion was not elicited by the odours which elicit the negative potentials.4. In Cl(-)-free Ringer solution, neither the positive potential nor the protrusion and secretion occurred.5. When 1-2 mM-Ba(2+) in Ringer solution was dripped on the epithelium, both the positive potential and the protrusion and secretion resulted. Subsequent application of chloroform vapour only advanced further disintegration of the secretory granules, but it elicited neither a new protrusion of the granules nor the positive potential.6. In the olfactory epithelium in which the olfactory cells had degenerated but the supporting cells survived, both the positive potential and the protrusion and secretion occurred, but the negative potential did not.7. It is concluded that Cl(-) entry which mainly generates the longlasting positive potential triggers the secretion of the supporting cell.

Adenocarcinomas of the olfactory glands were diagnosed in five dogs. The tumors had invaded the adjacent olfactory and prefrontal areas of the cerebral hemispheres. The masses consisted of large sheets of neoplastic epithelial cells separated by connective tissue stroma. In some areas there were hemorrhage and necrosis. The anterior parts of the cerebral hemispheres had been destroyed by the invasive neoplastic cells, and the white matter in the areas was very edematous. Review of the medical and veterinary literature yielded no description of tumors originating in the olfactory glands.

Autoradiographic labelling was used to investigate the primary olfactory projections in the mouse. Small pieces of gelatin foam soaked in [3H]proline were inserted directly into the cavity of the vomeronasal organ. At survival times from 6 h to 10 days, radioactive label was found over the vomeronasal nerves and the glomeruli of the accessory olfactory bulb. Conversely, when radioactive amino acid was applied to the main olfactory mucosa, the label appeared over the main olfactory nerves and the glomeruli of the main olfactory bulb. In both the main and accessory bulbs there was evidence for a transneuronal uptake of label in the external plexiform and mitral cell layers subjacent to the labelled glomeruli. This transneuronal uptake was heavier at longer survival periods.

Olfactory epithelium from three groups of C57B1/6J and SWR/J mice exposed once or twice daily to 10% cigarette smoke for six or nine days was examined at the ultrastructural level. Olfactory epithelium of SWR/J experimental mice was not affected by cigarette smoke. However, prominent alterations were noted in this epithelium of C57B1/6J smoke treated mice. These alterations included a reduction in size and (possibly) number of olfactory vesicles which sometimes failed to protrude above the epithelial surface and greatly reduced numbers of olfactory vesicle sensory cilia. In the supporting cell population an abnormal electron-lucent cell type was noted among the usually darker types. Both cell types were frequently found protruding abnormally above the epithelial surface. Microvilli of supporting cells were markedly reduced in number. The present study revealed that the olfactory epithelia in all mice of the same strain are not affected equally by acute smoke exposures. In affected animals the degree of morphological alteration suggests that normal olfaction might have been impaired. Strain differences in reaction to smoke insult indicate that susceptibility is genetically determined.

The nasal epithelia of two species of bats were quantified with respect to relative surface areas and olfactory epithelial volumes. In the macrosmatic Aribeus jamaicensis 55.9% of the nasal cavity surface was covered by olfactory epithelium (232.4 mm2), in contrast to only 28.9% in the microsmatic Myotis lucifugus (36.4 mm2). The roles of the various nasal epithelia have been discussed as they may relate to olfaction, respiration and echolocation. In the olfactory bulbs of both species, the estimated concentration of mitral cells approximated at 2,500/mm2 compared to an olfactory nerve concentration of 5/mm2. In Artibeus, calculated total volume of olfactory epithelium was on the order of 16 times greater than in Myotis, and Artibeus' olfactory bulb diameter was twice as great. These findings, together with previously published surface, volume and physiological relationships, suggest a developmental design mechanism for an olfactory bulb in which the number of olfactory receptors increases some 450-fold above an initially established ratio of 2:1 between receptors and mitral cells. Key governing factors could be requisite mechanical rigidity of the cribriform plate of the ethmoid bone and response thresholds of higher brain centers.

Peripheral deafferentation of the primary olfactory pathway by stringent intranasal irrigation with a zinc sulfate solution results in a marked decrease in olfactory bulb weight, shrinkage of the glomerular layer of the olfactory bulb and specific disappearance of the unique olfactory marker protein from the olfactory bulb. These changes are irreversible for several months. In contrast, no alterations were seen in the activities of 3 neurotransmitter-metabolizing enzymes, or in 16 high affinity ‘neurotransmitter’ uptake systems, or in the levels of cyclic nucleotides in the olfactory bulbs. Surgical removal of the olfactory bulb results in the rapid specific decrease of the level of the unique marker protein in the olfactory epithelium. This treatment does not cause any alteration in the normally low levels of 3 neurotransmitter-metabolizing enzymes in the olfactory epithelium. Perhaps the primary olfactory chemoreceptor neurons utilize a novel transmitter candidate at their synapses in the olfactory bulb.

Regeneration of olfactory epithelium was studied at the ultrastructural level in two different strains of mice (C57B1/6J and SWR/J) following destructive changes induced by nasal irrigation with 1% aqueous solution of zinc sulfate (ZnSO4). Three epithelial conditions were seen during the first four to 14 days following treatment: a "surface alteration" state characterized by changes at the apical ends of olfactory and columnar supporting cells, a "squamous-metaplastic" state, and a simple-squamous" state. In the latter two conditions, thought to represent regenerative states, cells contained inclusions similar to secretion granules in Bowman's glands. This observation supports earlier suggestions that new epithelial cells originate from these glands. Later regenerative changes consist of differentiation of new sensory cells and columnar supporting cells in an initially disorganized epithelium. This epithelium then changes to a normal, pseudostratified organization. Regeneration of the epithelium begins earlier and proceeds more rapidly in the SWR/J strain than C57B1/6J mice. Possibly, a genetic difference exists between strains. After 72 days the epithelium in both strains had regenerated.

Scanning electron microscopy, sometimes supplemented with transmission electron microscopy, was used to study the ultrastructural morphology of the extrapulmonary respiratory tract. Material for observation was taken from male rat respiratory tracts which were fixed in situ and critical point-dried. Goblet cells, brush cells, potential ciliated cells, ciliated cells, cornified vestibule cells and the olfactory mucosa could be distinguished by their characteristic surface morphologies. The distribution of these various cell types throughout the extrapulmonary respiratory tract is described. Transmission electron microscopy of material treated with ruthenium red reveals that a polyanionic surface layer coats all cilia, microvilli and the intervening cell surfaces on all cell types found in the nasal cavities, trachea and extrapulmonary bronchi.

By means of ultrastructural and autoradiographic observations from the olfactory mucosa of frog, it has been shown that olfactory receptor neurons as well as supporting cells are continuously replaced during the adult life of the animal. The severing of the olfactory nerve in adult frogs results in rapid degeneration of all mature olfactory neurons. An increased mitotic activity of the basal cells accompanies the degeneration of the mature neurons and precedes the regeneration of new neurons. The capability of these newly formed neurons to re-establish their connections in the olfactory bulb has been ascertained and the modalities of the process will be dealt with in a further report.

1. Prussian blue particles pass rapidly from the surface of the olfactory mucosa and within 2 minutes are found in the tissue spaces, in blood and lymph vessels, in the perineural spaces of the olfactory nerve fibers and in the subarachnoid space and pia-arachnoid membrane. 2. There is great affinity of pigment particles for the olfactory sensory cells. 3. Preliminary treatment of the olfactory mucosa with tannic acid does not alter the speed with which this absorption occurs. It does, however, cause an inflammation of the mucosa and appears to prevent the pigment from entering the olfactory sensory cells. 4. Both pneumococci and S. enteritidis pass through the olfactory mucosa and reach the tissue spaces, the vessels and the subarachnoid space with the same rapidity as the pigment. This can be demonstrated both microscopically and by distribution tests. They invade by passage between the cells of the mucosa and there is no apparent affinity of the organisms for the olfactory sensory cells. 5. Tannic acid treatment of the olfactory mucosa in no way alters this invasion of organisms through the mucosa. 6. The pantropic virus, equine encephalomyelitis, was detected in the forebrain as promptly as were pigment and bacteria; neurotropic viruses, however,—those of St. Louis encephalitis, rabies and louping ill,—were not demonstrated in less than 24 hours.

A comparatively recent electrophysiological technique for studying peripheral olfactory events is to record sustained negative potentials from the olfactory epithelium. This method is rapidly replacing the older technique of recording multifiber discharges from the olfactory nerve or bulb. Therefore, the extent to which the results from the two methods correlate with each other was studied by simultaneously recording from the nerve and from the mucosa under several conditions. Although most often parallel, some differences between the two measures were found. Their response maxima did not always temporally coincide. Their amplitudes did not always correlate. Certain stimuli reduced subsequent mucosal responses but not the neural. Repeated stimulation sometimes produced similar differences. Finally, the two responses were not linearly related as a function of stimulus intensity or flow rate. However, for reasons discussed, it is difficult to conclude that these discrepancies necessarily reflect unfavorably upon the reliability of the mucosal potential as the criterion measure of peripheral olfactory activity. Nevertheless, the mucosal potential should not be accepted unequivocally as such a criterion measure until it is more thoroughly understood.

The hamster nasal cavity consists of vestibular, non-olfactory and olfactory portions. Much of the non-olfactory nasal cavity surface is lined by cuboidal, stratified cuboidal, and low columnar epithelia, devoid of cilia. Goblet cells and ciliated respiratory epithelium are present over only a small portion of the nasal cavity surface. The largest glandular masses in the hamster nose are the maxillary recess glands, the vomeronasal glands and the lateral nasal gland 1; these three glands contain neutral mucopolysaccharides (PAS-positive). Other nasal glands contain both acidic and neutral mucopolysaccharides; the staining reaction for acidic mucopolysaccharide is stronger in goblet cells and olfactory glands than in the other nasal glands. The ducts which open into the nasal vestibule are the excretory ducts of compound tubuloacinar serous glands. The one major PAS-positive gland whose duct opens into the nasal vestibule is the lateral nasal gland 1. The ducts of the compound tubuloacinar vomeronasal glands open into the lumen of the vomeronasal organ, which is connected to the ventral nasal meatus by means of the vomeronasal duct. The ducts of the branched tubuloacinar maxillary recess glands open into the maxillary recess. Few ducts open into the caudal half of the nasal cavity.

Die vorliegende Untersuchung befast sich mit der Feinstruktur der Riechfalten von Calamoichthys calabaricus unter besonderer Berucksichtigung des Riech- und Flimmerepithels. — Das Flimmerepithel ist aus 3 Zelltypen aufgebaut: Flimmerzellen, wenigen Stutzzellen und Basalzellen. Die Flimmerzellen sind mitochondrienreich und tragen bis zu 160 Flimmerharchen pro Zelle. Diese Kinocilien besitzen an ihren Basalkorpern Zilienwurzeln, von denen ein Teil ins Zellinnere bis in Kernnahe zieht, wahrend der andere Teil parallel zur Oberflache verlauft und benachbarte Basalapparate verbindet. — Auch das Riechepithel, das gegen das Flimmerepithel scharf abgesetzt ist, besteht aus 3 Zelltypen: Rezeptoren, Stutzzellen und Basalzellen. Die Rezeptoren haben eine einheitliche Gestalt und Struktur. Sie sind schlank keulenformig und uberragen mit einer kleinen Vesicula olfactoria die Epitheloberflache. Seitlich sitzen an der Vesicula — unter konstant 25–27° Ablenkung von der Senkrechten — in der Regel 12 sensorische Cilien, die alle auf gleicher Hohe entspringen. Basal setzt sich das Rezeptorperikaryon in ein Axon fort. Die Axone mehrerer Rezeptoren vereinigen sich noch innerhalb des Epithels zu Bundeln, die durch die Basalmembran ins Bindegewebe ziehen. Die stark osmiophilen Stutzzellen des Riechepithels durchziehen das Riechepithel von der Basalmembran bis zur Epitheloberflache und tragen einzelne Cilien. Der verbreiterte Apikalteil der Stutzzellen enthalt zahlreiche Schleimvesikel, die auf eine sezernierende Funktion dieser Zellen hinweisen. Die praparative Behandlung von Riechepithelien wird kritisch diskutiert.

1. Differences in unitary spike conformation were systematically investigated with extracellular recordings at different depths in the frog's olfactory epithelium. Platinum-black metal-filled micro-electrodes were used in the unit recordings. Their properties were carefully investigated and compared with those of micropipettes. 2. Three basic types of spikes were recorded: a diphasic spike with a positive—negative voltage sequence, a diphasic spike with a negative—positive voltage sequence and a triphasic spike with a positive—negative—positive voltage sequence. 3. The triphasic spike was correlated with the action potential in the axon. The initially negative diphasic spike was correlated with the action potential initiated in the cell body region. The initially positive diphasic spike was correlated with the spread of the impulse into the receptor cell dendrite. 4. A model is discussed which accounts for the differences in spike conformations and provides a basis for analysing impulse activity in spontaneously active and stimulus-driven olfactory receptor cells.

Summary. 1 The relationship between the olfactory stimulating effectiveness and the chemical and physical properties of a number of odorous compounds has been studied. As a measure of the eff iciency has been taken the magnitude of the slow potential evoked in the olfactory mucosa in the frog. Aliphatic alcohols of equimolar concentrations were found to be increasingly stimulating up to a certain maximum with increasing chain length. A similar increase was also found for aldehydes and ketones while in the series of fatty acids the relation between stimulative effect and chain length was less regular. It was further found that the partial vapour pressures for alcohols of equal stimulating power increase approximately linearly Kith the saturated vapour pressures. In terms of thermodynamic activities the alcohols of intermediate chain length are equally stimulating while the lower alcohols are less effective. 2 The relationship between the different molecular parameters and the olfactory stimulative power of the studied compounds is discussed and the similarity between the results obtained in the present investigation and those in studies of olfaction in insects is pointed out.

The gradient of activity produced along the olfactory mucosa by odorant stimulation was measured by the ratio (the LB/MB ratio) of the summated neural discharges recorded from two branches of the olfactory nerve, a lateral branch (LB) supplying a mucosal region near the internal naris and a medial branch (MB) supplying a region near the external naris. Twenty-four frogs "sniffed" sixteen different odorants, each odorant at four concentrations and two flow rates. Increases in concentration and flow rate produced statistically reliable increases in the ratios; the magnitude of these increases was considerably smaller than the magnitude of the statistically significant changes that could be achieved by shifting the odorants themselves. Even the small change due to concentration depended upon the odorant presented. Thus, even at the highest physiologically possible concentrations and flow rates, the general level of the activity gradient along the mucosa appeared to be determined mainly by the particular odorant used. The relative retention time of each of these 16 different odorants was measured in a gas chromatograph fitted with a Carbowax 20M column. In general, the longer the odorant's retention time the smaller its LB/MB ratio. This suggests that the different mucosal gradients of activity are established for different odorants by a chromatographic process. The data further suggest that the mucosa behaves like a polar chromatographic column.

Introduction: Esthesioneuroepithelioma is a rare tumor, which is not very clearly defined but considered to be of neural origin. About 125 cases have been described. A tentative classification proposed by WHO is ranging these tumors under the heading of “olfactory neuroblastoma”, mentioning results obtained in experimental carcinogenesis in hamsters and rats. For a better definition of these tumors, this paper gives a morphological description of tumors induced with diethylnitrosamine in the nasal cavity of hamsters. Methods: Fourty hamsters were repeatedly injected with diethylnitrosamine. The experimental animals were perfused with formol and glutaraldehyde under anesthesia as soon as symptoms of tumor growth were visible. The tumors were analyzed by light and electron microscopy after partiale decalcification of the head. A few tumors were transplanted and cultured in vitro. Results: Tumors of the trachea were papillomas; hepatocellular carcinomas and cholangiocarcinomas were found in the liver, the respective benign tumors were adenomas. Within the nasal cavity, three types of malignant neoplasias were met: squamous cell carcinomas, adenocarcinomas and “neurogenic tumors”. One adenocarcinoma has been investigated by electron microscopy, signs of a well differentiated blastoma were found. “Neurogenic tumors” were divided light microscopically into neuroepithelioma or medulloepithelioma tumors and “neuroblastoma-like tumors”. In the first group, true rosettes and hollow spaces, lined by epithelial cells, occur. Anaplastic epithelial tumors with and without rosettes could be differentiated by electron microscopy. Transplanted tumors of neural origin grew only in three generations. In vitro, small stellate cells were found, but cellular processes disappeared within few hours leaving round cells which did not change over a long period. Discussion: Morphological and ultrastructural analysis shows epithelial characteristics and formation of rosettes. Early stages of tumorous growth indicating its origin from the olfactory mucosa were found in few instances. The range of nasal tumors in the classification scheme is discussed, but will be the broad subject of a following paper.

Electrical activity and histological changes were studied in the degenerating olfactory epithelium of the bullfrog after the olfactory nerve had been sectioned. After nerve section, the electrical responses to odors disappeared in the olfactory epithelium in 8 days in the summer, in 11 days in the early autumn, and in 16 days in the early winter. In the degenerating olfactory epithelium a striking decrease in the number of olfactory cells was found, but not of supporting cells. The ratio of the number of olfactory cells to that of supporting cells was found to decrease from 5 or 6 to below 2 after the nerve section. At a ratio below 2, the electrical responses to odor disappeared. The histological changes in the bullfrog are compared with those in the mouse and rabbit. The localization of the olfactory pigment and the electrical activity of the supporting cell are discussed. It was concluded that all three types of responses to odors originate from the activity of the olfactory cell.

Anatomical differences in olfactory structures point to a more highly developed olfactory sense in the frugivorous bat Artibeus jamaicensis than in the insectivorous bat Myotis lucifugus. Artibeus' nostrils show greater potential for differential control of nasal airstreams. Its nasal cavities, in contrast to Myotis, are clearly demarcated into olfactory and respiratory portions. Both species have seven turbinals, but of the five ethmoturbinals, Artibeus has four endoturbinals and one ectoturbinal whereas Myotis has three and two, respectively. The configuration and histology of the more complex turbinals of Artibeus indicates a greater surface area of olfactory epithelium. The nasal epithelia are thicker in Artibeus. Olfactory receptors appear similar in both species but the thickness and composition of the olfactory epithelium in Artibeus suggests the presence of about twice as many receptors per unit area. This is also reflected in the relative prominence of olfactory nerve bundles. From these and other bulbar relationships we conclude that the proportion of fila olfactoria to large mitral cells, as reflected by the olfactory bulb glomeruli, is some function of a fundamental 2:1 relationship. Nasal glands, with flaps covering two of their more prominent ducts, and blood vessels are more pronounced in Artibeus. This presumably correlates with the nasal type of phonation exhibited by this bat as well as a greater ability to condition air per se. Nasopalatine ducts exist in both species but only Artibeus has a vomeronasal organ. A diffuse ganglion accompanies the organ; some of its neurons are associated with the unmyelinated vomeronasal nerve, whereas others are intraepithelial. The vomeronasal nerve terminates in a prominent accessory olfactory bulb.

SUMMARY In mouse and fish olfactory mucosae, lanthanum has been found to penetrate various intracellular components of cells including the endoplasmic reticulum, mitochondria, microvilli, microtubules and cilia, outlining their substructure in negative contrast when seen in sectioned specimens. Structural details approaching those seen in disrupted negatively stained material were observed in sections, suggesting that intracellular lanthanum staining may prove a useful tool in morphological studies.

The functional relation between the olfactory bulb and the mesencephalic reticular formation (RF) was studied in curarized rabbits. The results obtained in the acute experiment were confirmed in the chronic experiment.1. High frequency stimulation in the RF suppressed the intrinsic and the induced waves of the olfactory bulb. Peripheral arousal stimuli were sometimes effective in causing a similar changes in the olfactory activity.2. The excitable spots suppressing the activity of the bulb were distributed diffusely in the RF. They were also found to extend in the hypothalamus.3. RF stimulation failed to modify the negative wave potential of about 40 msec duration evoked in the bulb by electrical stimulation of the olfactory mucosa.4. Complete destruction of the olfactory mucosa and section of the anterior commissure were unable to influence the suppression of the olfactory activity due to RF stimulation. On the other hand, neuronal isolation of the bulb abolished the reticular influence.5. In contrast to the neocortical EEG, the olfactory activity failed to show a release phenomenon upon acute destruction of the RF.6. In the chronic experiment peripheral arousal stimuli were found to suppress the intrinsic activity of the olfactory bulb in the same manner as in the acute experiment.A part of the expense of this work was defrayed by a grant of the Ministry of Education.

The potential changes induced in the frog's olfactory nerve and bulb by electrical stimulation of the nasal mucosa have been studied. The response developed by the bulb is composed of two successive negative deflections. It has been possible to segregate these deflections and partly identify their origins. The first component of the response is of synaptic nature and builds up a persisting potential during repetitive stimulation. The second component of the response is sensitive to the action of narcotics and asphyxia and is blocked when secondary neurons are stimulated antidromically. The conclusion has been drawn that this component represents the propagated activity in neurons of secondary order. The properties of the olfactory nerve fibres have been studied in recordings of the nerve action potential.

Bilateral olfactory bulbectomy eliminates mating and attenuates intermale investigatory and aggressive behavior in male golden hamsters (Mesocricetus auratus). Two reversible methods of peripheral olfactory blockage were found to mimic these effects. They were (1) unilateral olfactory bulbectomy combined with contralateral nostril occlusion and (2) bilateral reversible destruction of the olfactory epithelium by zinc sulfate infusion. These results indicate that a primary sensory deficit is sufficient to explain the effects of bulbectomy on social behavior and that incidental disruption of central nervous system tissue need not be invoked.

Qualitative and quantitative aspects of the normal fine morphology of the olfactory receptor cells. their cilia, axons, and neighboring cells, were investigated in the burbot. The receptor cells lacked olfactory tubercles and microvilli; they were isolated from each other by supporting and basal cells. The role of cilia and microvilli in chemoreception was discussed. Zonulae occludentes between the epithelial cells sealed off the interior of the olfactory mucosa of this fresh water animal from an environment with low osmotic activity. The number of receptor cells was estimated to be about 73 per 1,000 μ2. Glial cell processes penetrated from the connective tissue, investing small bundles of receptor axons within the epithelium. Formation of the filum olfactorium was described. The average number of axons in the central portion of the olfactory nerve was about 29 per μ2 in areas free of glial cells and connective tissue. The mean diameter of the axons in the nerve proper was 0.136 μ whereas a higher average was found beneath the epithelium. The presence of mitochondria imparted a considerable skewness to the distribution of diameters. The calculated total number of axons in the olfactory nerve corresponded with the number of receptor cells. The convergence of olfactory nerve fibers upon secondary neurons with myelinated axons was estimated to about 1,000:1.

The olfactory epithelium and the afferent nerve fibers to the olfactory lobes were destroyed in one group of rats, while in another the olfactory peduncle was destroyed bilaterally. Following either o

1. Bei 4 Herden des deutschen Schwarzkopfschafes in Deutschland (Schlesien, Hessen und Lippe) wurden endemisch auftretende Adenopapillome der Riechschleimhaut bei 2–15% der Tiere festgestellt. Eine Rassendisposition liegt jedoch nicht vor, da auch andere Rassen spontan und experimentell erkranken konnen. 2. Nach einer wahrscheinlich primaren entzundlichen lymphocytaren Infiltration der Schleimhaut folgt eine Adenom- und dieser eine Papillombidldung von expansivem Wachstum. 3. Experimentell konnten die Geschwulste durch eine Aufschwemmung und durch zellfreie Filtrate durch Instillation in die Siebbeingegend auf gesunde Schafe ubertragen werden. 4. Die Art des infektosen Agens ist noch unbekannt. Wahrscheinlich handelt es sich um ein Virus.