Abstract
LONDON. Royal Society, February 9.—Sir Archibald Geikie, K.C.B., president, in the chair.—V. H. Veley and W. L. Symes: Certain physical and physiological properties of stovaine and its homologues. The bodies in question comprise the methyl-, amyl-, phenyl-, and benzyl-homologues of stovaine, and in addition a new compound recently prepared by M. Fourneau, viz. the propyl ester of dimethyl-amino-oxy-benzoyl-isobutyric acid. The densities of these diminish with increasing molecular weight, and the affinity value of the last-named is less than that already found by the former of the authors for stovaine and for its methyl homologue. Fourneau's new compound abolishes the contractility of muscle less rapidly than does stovaine or methyl-stovaine. It has also less effect on blood pressure and on respiration. Amyl-, phenyl-, and benzyl-stovaine appear to act more slowly on muscle than does stovaine, presumably on account of partial precipitation of their bases. On blood pressure, amyl-stovaine has rather more effect than has stovaine. The pronounced local anaesthetic properties possessed by all these bodies are discussed in the following paper.—W. L. Symes and V. H. Veley: The effect of some local anæsthetics on nerve. The bodies dealt with in the preceding paper have been compared with one another, and also with cocaine, as to their effects in blocking the physiological conductivity of frog's nerve. The anæsthetic block produced by these bodies, when complete for maximal single stimuli (Berne coil at 400 mm.), is also complete for single stimuli many times more intense (Berne coil at 200—100 mm.), A block complete to maximal single stimuli (coil at 400 mm.) is usually also complete to repeated stimuli with the same disposition of the coil. Partial blockage of individual nerve fibres has not been detected. Stovaine, its homologues, and Fourneau's new salt all block more actively than does cocaine. Stovaine, methyl-stovaine, and Fourneau's new salt block more rapidly than do the remaining bodies. Amyl-, phenyl-, and benzyl-stovaine block more slowly, and the resulting block is less rapidly washed out. Considered as local anæsthetics, phenyl- and benzyl-stovaine offer no advantage over the remaining bodies. Amyl-stovaine may be of value on account of the relatively long duration of its effect. Methyl-stovaine is the least readily decomposed by faintly alkaline fluids such as lymph and cerebro-spinal fluid. Fourneau's new salt has the least effect on circulation and on respiration.—F. F. Blackman and A. M. Smith: Experimental researches on vegetable assimilation and respiration. VIII.—A new method for estimating gaseous exchanges of submerged plants. The plant is enclosed in a glass chamber, a current of water is kept flowing through the chamber, and samples of the affluent and effluent liquid are analysed at frequent intervals. The alteration in the amount of CO2 in solution which the liquid undergoes in passing over the plant in the chamber is the measure of the respiration or assimilation that is taking place. For experiments on assimilation, the liquid supplied to the chamber can be enriched with any desired amount of CO2, and by a special use of a CO2 generating tower the amount of this gas dissolved can be kept constant for a long period of time. The glass chamber containing the plant is sunk in a large copper water-bath with a glass window, and the temperature and illumination can be controlled. When the conditions allow vigorous assimilation, much oxygen is given off as bubbles from the plant in the chamber, and these bubbles take up an appreciable amount of CO2 from the solution. It is therefore necessary to collect and measure this gas and use it as a correction to the apparent diminution in the dissolved CO2. The gas is separated from the liquid by a valve at the highest point of the apparatus, and collected automatically for analysis. This method has none of the limitations of the bubble-counting procedure exclusively employed previously for the investigation of the assimilation of water-plants, and, since it takes account of the CO2 in solution and also of that in the gas bubbles, critical measurements can now be made of the assimilation throughout the whole range of the external factors that primarily control this function.—F. F. Blackman and A. M. Smith: Experimental researches on vegetable assimilation and respiration. IX.—On assimilation in submerged water-plants and its relation to the concentration of carbon dioxide and other factors. The experiments were carried out by a new method, which takes account of the alteration of the gases in solution as well as of the gases liberated as bubbles. The aim is to demonstrate the nature of the relation between assimilation and the chief environmental factors—CO2 supply, light-intensity, and temperature. The relation is such that the magnitude of this function in every combination of these factors is determined by one or other of them acting as a limiting factor. The identification of the particular limiting factor in any definite case is carried out by applying experimentally the following general principle:—When the magnitude of a function is limited by one of a set of possible factors, increase of that factor, and of that one alone, will be found to bring about an increase of the magnitude of the function. From the data obtained, a new type of diagram is constructed, by which it is possible to foretell what value of assimilation in Elodea will be attained in any combination of medium magnitudes of the three factors of the environment. In this diagram, against the different values of assimilation as ordinates, are ranged three separate curves showing the degrees of CO2 supply, temperature, and illumination, which are respectively essential for the attainment of each value of assimilation. For any hypothetical combination of the factors, it follows, by the principle of limiting factors, that if the three functional values corresponding potentially to these be ascertained from the diagram, then the actual magnitude of assimilation attained with that combination of factors will always be the smallest of the three potential values. The last section contains a critical account of the work of previous investigators who interpreted their results on the assumption that there was a primary optimum in the relation between assimilation and each external factor. The substantial work of Pantanelli led him to the conclusion that the position of the optimum for any one factor shifts with the magnitude of the other concurrent factors. This can only be a transitional point of view, and from this we have advanced to the standpoint that the whole conception of optima in this connection is inapplicable, and breaks down completely on careful analysis. The authors show in detail that all the experiments of previous workers are more harmoniously interpreted from the point of view of interacting limiting factors than by the conception of optima.
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Societies and Academies . Nature 85, 529–532 (1911). https://doi.org/10.1038/085529a0
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DOI: https://doi.org/10.1038/085529a0