Sur l'apogéotropisme du Phycomyces

Summary Under definite conditions of culture, growth of sporangiophore of Phycomyces has been investigated by Shadowgraphic method. During sporange formation, the rate of growth is the smallest (Fig. 1). The apogeotropic sensitivity of sporangiophores is the greatest before sporange formation; presentation and reaction times increase with age and strongly with light pre-treatment (Fig. 2, 3). Auxin could be responsible for apogeotropic reactions of Phycomyces.     

Composition du suc de décongélation du muscle strié de la grenouille

Summary Because of cell membrane destruction, fluid escaping a muscle on thawing contains a large amount of proteins (myogen and globulin X). Whilst usual gradientsa, b, andc are present in the fluid, the gradientsd ande also occurring in extracts of unstimulated frog muscles are replaced by the gradientx already found in extracts of in N₂ exhausted muscles.     

L'action de l'hypoglycémie sur l'électrorétinogramme du lapin

Summary Hypoglycaemia in the rabbit due to an intravenous injection of insulin results in an important diminution of the value of theb wave in the ERG (up till 80%). Nevertheless, this phenomenon does not follow directly upon the lowering of the blood glucose level but takes place, on the average, about 2 h later. This fact is explained by the enormous energy reserves of the retina, the lowering of the ERG taking place only when these reserves are exhausted.

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Travail subventionné par la FondationEmil Barell (Bâle).     

Contribution à l'étude d'une propriété répétitive du cerveau

Summary While pursuing the study of cortical functioning by the EEG. and after-image methods, we have come to believe that every stimulation evokes in the corresponding area of the cortex not only a simultaneous excitation but also acontinued action, i.e. after stimulation, several successive excitations of progressively diminishing intensity appear in the same area of the cortex.We have investigated the continued groups appearing on corticographical tracings taken from different cortical areas of the experimental animal (the rabbit) after various forms of stimulation (auditory, electrical, and visual). By comparing them with the after-images seen by human subjects in EEG. experiments, we have been led to identify the two phenomena.In order to carry this study further, we have undertaken two series of corticographical experiments, recording tracings takensimultaneously from the parietal and striate areas of the rabbit. The first series was intended to study the effects on the tracings of visual stimuli. The second was concerned with the effects on the same tracings of weak electrical stimuli.

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Nous avons consacré à cette propriété répétitive du cerveau une note parue dans les Comptesrendus de l'Académie des Sciences, Juillet 1955, Paris — dont le présent article constitue le développement.     

L'action du 2,4-dichlorophénoxyacétate de sodium sur les végétaux

Zusammenfassung 0,5prozentige Lösungen von 2,4-dichlorophenoxyessigsaurem Natrium verhindern das Keimen vonAgrostemma Githago, Hordeum vulgare undTriticum vulgare. Das Wachstum junger Pflanzen der drei Arten wird durch Verpflanzen auf mit 0,5prozentigen Lösungen dieses Stoffes getränktem Sand gehemmt. Schwächere Lösungen gestatten das Wachstum, es ist aber verlangsamt und die Pflanzen tragen Mißbildungen verschiedener Art, die an die nach Einwirkung von Colchicin und Heteroauxin beschriebenen erinnern. Stark verdünnte Lösungen (5·10^–6) beschleunigen das Wachstum und regen die Wurzelbildung an; diese Wirkung ist beiHordeum vulgare besonders deutlich.     

Action d'un inhibiteur de la carboanhydrase,l'acétazolamide,sur l'excitabilité du cortex,du thalamus et du rhinencéphale

Summary The electrical activity induced by stimulation of the cortex, diencephalon and rhinencephalon was studied in the rabbit under the influence of a carbonic anhydrase inhibitor, acetazolamide or Diamox. A significant decrease of the excitability was found in the diencephalon.The rapidity and the electivity of this action, as well as the blood pH variations simultaneously registered, suggest a specific inhibition of cerebral carbonic anhydrase by Diamox, although a participation of the metabolic acidosis cannot be fully excluded.     

Propriétés chitinolytiques du liquide exuvial du ver à soie (Bombyx mori L.)

Summary The authors add further confirmation to the hypothesis of the role played by a chitinase during the process of moulting. By ligaturingBombyx mori-larvae between head and thorax, accumulation of moulting fluid takes place between the larval and nymphal cuticles, swallowing of this fluid being prevented. The chitinolytic properties of this moulting fluid are demonstratedin vitro. The activity of chitinase at different pH is investigated: the optimum pH lying at about 5.4.     

L'action du dithizone sur la rétine du lapin Etude électrophysiologique

Summary Dithizone provokes chorio-retinal lesions in the rabbit, visible ophthalmoscopally after 12 h and microscopally after 8 h. The ERG reveals much earlier alterations, theb wave diminishes rapidly and the ERG is abolished in 3 to 4 h. In the cases where no durable lesions are noted, the ERG is nevertheless pathological, theb wave being diminished 40 to 70% of its initial value during the first day, but becoming normal once again even if a permanent diabetes results. These anomalies of the ERG are related to acute hypoglycaemia and enzymatic blockage.

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Travail subventionné par la FondationEmil Barell (Bâle).     

Fixation et inclusion du matériel nucléaire deEscherichia coli

Zusammenfassung In Abhängigkeit vom pH der Fixierungsflüssigkeit und vorhandener Kationen zeigt der Bakterienkern in Dünnschnitten entweder eine grobe oder aber eine feine Innenstruktur. Die als Chromosomenstrukturen gedeuteten Koagulationsbilder werden erneut in Frage gestellt.     

Relations du « métabolisme respiratoire » des bactéries et du type de bactériophage avec l'activité de substances antiphages

Summary Quantitative determination of bacteriolysis with different T_1–7-phages confirms earlier observations that with substances inhibiting the action of T₁-phage the normal respiratory metabolism of the protected bacteria is quantitatively restored in every detail.With T₂-phage, showing a different respiratory course of bacteriolysis, no effect is obtained with the same substance, either on the respiration of the bacteria or on the typical course of respiration during bacteriolysis. The action of the phage inhibiting substance against T₁-phage is therefore an effect of definite specificity.     

Activité staphylostatique de composés du groupe des benzophénarsazines

Summary It is shown that certain compounds belonging to the group of angular benzophenarsazines display a high specific bacteriostatic activity towardsMicrococcus pyogenes var.aureus. This biological property provides a further ground of similarity between these compounds and one of their structural analogues, 3,4–5,6-dibenzocarbazole.     

Présence d'uraninite dans les minéraux accessoires du granite de baveno

Summary Microscopic crystals of uraninite are found in the accessories of the Baveno granite by the nuclear photographic emulsion technique. The uraninite is believed to be a primary mineral of the granite, its concentration in the sample is less than 1 p.p.m. but it contributes about 10% of the total activity.     

L'électrophorèse sur papier des protéines hydrosolubles du cristallin

Summary By using paper electrophoresis, the authors succeeded in demonstrating different protein fractions in human and animal lenses.Qualitative and quantitative differences were noted in different animals, between the cortical and the nuclear areas of the lens, and also according to age.

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Chargé de Recherches du Fonds national de la Recherche scientifique.     

Paléotempératures indiquées par l'analyse isotopique de fossiles du crétacé inférieur des Hautes-Alpes (France)

Summary Paleotemperature determinations were made by the oxygen isotope method on 20 Belemnoids, 5 Aptychi and a Nautilus beak from the Lower Cretaceous of the Dévoluy area of the Hautes-Alpes (France). The data derived show a well-defined trend from higher temperatures in the Berriasian to a climatic minimum in the Barremian followed by a rise to the Albian maximum, previously observed elsewhere in Europe. The Aptychi are shown to be useful paleotemperature indicators utilizable in conjunction with Belemnoids. A Sequanian Aptychus gave a high temperature reading, indicating that the climate steadily cooled from Upper Jurassic times into the Barremian. The single Nautilus beak gave a result suggesting that this group of fossils may also prove valuable in similar studies in the future. The paleotemperature data also showed (by the stratigraphic position of the relevant Belemnoids) that the Aptian is either very attenuated or absent in the Dévoluy.     

Analyses immunoélectrophorétiques des fractions protéiques du sérum humain séparées par électrophorèse en gel d'amidon

Summary Human plasma components, separated by starch gel electrophoresis, are eluted and concentrated by lyophilisation. Immuno-electrophoretic analysis shows that certain of these fractions are immunologically heterogenous. The authors point out that this immunological criterium should be used before employing an eluted fraction, even if it appears electrophoretically homogenous.      

Varignon ou la théorie du mouvement des projectiles ‘comprise en une Proposition générale

Cet article a pour objet de montrer la nouveauté du traitement varignonien du mouvement des projectiles dans les milieux résistants par rapport au traitement de ce problème présenté entre autres par Newton dans les Principia. Aussi, après avoir analysé cursivement différentes Propositions du Livre II des Principia, nous étudierons plus spécialement, dans les Mémoires présentés par Varignon à l'Académie Royale des Sciences entre 1707 et 1711, la mise en place de l'expression d'une ‘Proposition générale’. Nous montrerons ensuite sur quelques cas particuliers en quel sens on peut dire que l'étude du mouvement des projectiles dans les milieux résistants se réduit alors, pour l'essentiel, à de simples questions d'intégration et de différentiation.     

Sur L'origine du ‘Principe Général’ de Jean Le Rond D'Alembert

This article intends to propose new hypotheses concerning the origin of the ‘Principe général’ of mechanics of Jean Le Rond D'Alembert expressed in its Traité de dynamique in 1743. The examination of the statics of Pierre Varignon and its inheritance suggests that D'Alembert retains, through a case of oblique collision on a hard surface, a method of decomposition and equilibrium of forces which is close to its principle. On the other hand, this principle requires a definition of the equilibrium widely spread in the 17th and 18th centuries, D'Alembert seeming then more to innovate from an epistemological point of view that on a technical one. Finally, the determination of rules of collision based at the same time on decompositions of movements at the level of the centre of mass and on appeal to a principle of relativity constitutes a know-how at the beginning of the 18th century which can be moved closer to methods developed by D'Alembert. These three aspects try then to replace the science of D'Alembert in a context by insisting on the essential role of the collisions of body and on that of the notion of equilibrium concerning the birth of its principle.     

Analyse expérimentale du développementin vitro des germes plumaires de l'embryon de poulet

Zusammenfassung Die Differenzierung der Dunen des Hühnerembryos lässt drei Phasen erkennen: 1. Eine der Haut fremde Anregung löst im Corium die Bildung der Dunenanlagen aus; 2. diese Dunenanlagen üben eine kurzfristige induzierende Wirkung aus, die die Epidermis zur Ausbuchtung der Dunen veranlasst; 3. die auswachsende Dunenepidermis kommt dann selber zur Induktionsaktivität und bewirkt das Eindringen der Coriumzellen in den in die Länge wachsenden Epidermiszylinder.