Excitation Phenomena Research Articles

Potassium in the Brain in Vitamin B1 Deficiency

IT has been stated that there is increased amount of potassium in the brains of pigeons suffering from vitamin B1 deficiency. In view of the general interest attached to potassium salts and phenomena of excitation, I have re-examined this question. Unfortunately, I cannot find any significant difference between the amounts of potassium in the brains of normal and vitamin B1 deficient pigeons, the values being 3.6 mgm. per gram of tissue in each case. The changes obtained by these authors1 cannot, therefore, have been due to the avitaminosis.

PHYSICO-MATHEMATICAL ASPECTS OF EXCITATION AND CONDUCTION IN NERVES

Although phenomena of excitation have long been considered as falling into the domain not only of the biologist but also of the physicist and mathematician, the situation has been different until recently with regard to phenomena of nerve conduction, and this in spite of the circumstance that there is a rather imposing array of evidence tending to show that the propagation of the nerve impulse is due to the excitation of adjacent unexcited regions by action current, produced by the electro-negativity of the region already excited. Without committing ourselves to either the acceptance or rejection of this hypothesis, we may legitimately investigate the mathematical and quantitative aspects of the latter.

Self excitation of a frequency converter

After a general discussion of the phenomenon of self excitation of a-c machines, a specific case of 3 phase self excitation of a Scherbius machine is treated. Such a machine is used in the regulating set of a variable-ratio frequency converter for inherently constant power transfer, the operating features of which are described. Under certain conditions this converter may be subject to the danger of self excitation. These conditions are discussed in detail and means are indicated to prevent self excitation during the normal operation of this converter.

Self Excitation of a Frequency Converter

After a general discussion of the phenomenon of self excitation of a-c machines, a specific case of 3 phase self excitation of a Scherbius machine is treated. Such a machine is used in the regulating set of a variable-ratio frequency converter for inherently constant power transfer, the operating features of which are described. Under certain conditions this converter may be subject to the danger of self excitation. These conditions are discussed in detail and means are indicated to prevent self excitation during the normal operation of this converter.

The nuclear photoelectric effect

Some time ago we reported in ‘Nature’ the observation of a nuclear photo-effect, the disintegration of the deutron by γ-rays. An effect of y-rays upon complex nuclei might be expected to occur from analogy with the phenomena of excitation and ionization of atoms by light, and such an effect has been looked for from time to time by various investigators. A necessary condition to make disintegration possible is that the energy of the γ-ray quantum must be greater than the binding energy of the particle which is to be removed from the nucleus. The most energetic γ-rays which are readily available in sufficient intensity are those of thorium C", which have an energy hv — 2·62 x 10 6 electron volts. One can hope, therefore, using these γ-rays, to produce disintegration with the emission of a heavy particle, such as a neutron, proton, etc., only in those nuclei which have a small or negative mass defect, such as the nuclei of deuterium, beryllium, and those radioactive elements which emit α-particles. In fact, only the nuclei of deuterium and beryllium have so far been disintegrated in this way. The disintegration of beryllium by the γ-rays of radium was first reported by Szilard and Chalmers. No evidence of a photo-electric disintegration amongst the radioactive elements has yet been found.

The excitation of band systems by electron impact

The relative positions of the more intense bands of a system in the usual square array can be predicted by classical methods (the Frank-Condon principle) from the potential curves for the initial and final states. This procedure is upheld in its essentials by wave mechanics, and a further wave mechanics development permits the calculation of transition probabilities in emission in band systems of symmetric diatomic molecules. The essential features of the theory are that relatively massive nuclei may be assumed not to respond immediately to changes in the electronic arrangement of the molecule, and that one need not evaluate that part of the electric moment directly concerned with such electronic rearrangements. These circumstances reduce the problem to one for simple oscillators with known potential functions. For a complete theory of the relative intensities , however, the details of the accompanying phenomenon of excitation must be known. While these are necessarily extremely complicated for bands emitted from different initial electronic states, a considerable simplification may be expected for bands emitted from the same electronic state. The problem of the relative excitation probabilities then forms the excitation analogue of the Frank-Condon principle.

Total secondary electron emission from polycrystalline Nickel

The importance of secondary electron emission in its relation to the excitation of soft X-rays has been pointed out in a recent paper by Prof. O. W. Richardson. He has shown that at every potential where there is an increased excitation of soft X-rays, there is correspondingly an increase in the emission of secondary electrons, and has discussed at some length the mechanism of the generation of secondary electrons. It was therefore felt that a much clearer idea of the phenomenon of soft X-ray excitation from metallic surfaces could be had by studying the secondary electron emission from polycrystalline and single crystal faces. As early as in 1908 Richardson showed that slowly moving electrons are reflected in considerable proportion from metallic plates. Davisson and Kunsman, in a series of papers commencing from 1921, showed that at low voltages up to about 9 volts most of the secondary electrons were purely reflected electrons with velocities the same as the incident electrons. The percentage of the reflected electrons fell rapidly as the applied potential was increased above 9 volts, while that of low velocity electrons increased steadily. Farnsworth, with improved apparatus, added much valuable information regarding the generation of secondary electrons and the conditions operating in such cases. These observers showed that the total emission of secondary electrons from a metal surface depended on the applied potential, the nature of the surface and the previous heat treatment of the metal. They also found that the ratio of the secondary beam to the primary increases with applied potential and becomes greater than 1 after a certain potential, depending on the nature of the bombarded metal, is reached.

Experiments on the excitation of light by low voltage positive rays

Although the ionisation and excitation by low voltage electrons have been extensively studied experimentally, and the general course of these processes is fairly well mapped out, the phenomena of ionisation and excitation by slow positive ions have so far been but little attacked, and what experimental material exists is rather inconclusive. The well-known formula for the current in a cumulative gaseous discharge was based upon the assumption that slow positive ions were capable of ionising the gas molecules they struck; and the accuracy with which this formula fitted the experimental results was taken as good evidence for the physical assumptions leading to it. But Holst and Oesterhuis have suggested that in addition to the ionisation produced by the moving positive ions the secondary electron emission from the cathode produced by the impact of positive ions (a phenomenon otherwise demonstrable) plays an important rȏle. This process, if it occurs, must render uncertain any quantitative conclusions as to ionisation by positive ions drawn from the classical formula.

On reciprocal innervation of antagonistic muscles.―Eighth note

The following note deals more especially with observations on inhibition occurring in instances of "reciprocal innervation" obtained as a spinal reflex reaction. My view is that inhibition of this kind is part and parcel of the normal reflex process, so that in a reflex it goes on side by side with excitation of other muscles opposed to those which are inhibited. One main consideration which supported the view is the correspondence of the skin-fields whence the reflex contraction of the one set of muscles and the inhibition of the opposed set of muscles can be elicited. So, also, the correspondence of the afferent nerve-trunks, and of the points of surface of the central nervous system whence are elicited the two effects. But to test the view further, I have now attempted to examine in some particulars the conditions attaching to the initiation, and the course run by the two phenomena under comparable circumstances. I. Even in one and the same spinal region the modes of origination, time-relations, etc., of the several elicitable, e. g ., in the dog's hind limb, the "extensor thrust," the "direct-flexion reflex," the "scratch reflex," differ so greatly for each of the types as compared with the others, that in order to compare the inhibition phenomenon with the excitation phenomenon it is important to take both the phenomena from the same type-reflex. The type-reflex I have taken for the purpose has been the "direct-flexion reflex" of the hind limb.

N. Bubnoff and R. Heidenhain on Phenomena of Excitation and Inhibition in the Cerebral Motor Centres

N. Bubnoff and R. Heidenhain on Phenomena of Excitation and Inhibition in the Cerebral Motor Centres

Societies and Academies

PARISAcademy of Sciences, July 14.—M. Daubrée in the chair.—The following papers were read:—Addition to my memoir on the principle of least action, by M. Serret.—On the direct combination of cyanogen with hydrogen and the metals, by M. Berthelot Cyanogen and hydrogen, pure and dry, mixed in equal volumes, and sent through a narrow glass tube heated to 500° to 550°, give some sign of combination; but the reaction is mor complete when the mixture is heated several hours to the same temperature in a sealed tube of hard glass; this is after-wards opened over mercury. The union of Cyanogen with some metals was found also to be merely a question of time and temperature. The substances were heated together m a sealed tube. Silver and mercury did not combine with cyanogen at any temperature. The analogies of cyanogen with the halogen substances are extended in this inquiry, beyond formulæ, to methods of direct stannamyls, by MM. Cahours and Demarcay.—On an application of the theory of elliptic functions, by M. Picard.—Researches on the effects of the rheostatic machine, by M. Planté. Using a machine of 80 condensers charged by his secondary battery of 800 couples, he obtains noisy sparks more than 0.12m. long, and if they are produced above an insulating surface sprinleled with flowers of sulphur, they may even attain 0.15m., and leave a sinuous furrow. When short of their maximum length they often from closed branches like anastomoses; also, on the sprinkled surface, arborescences, which appear after removing the excess of sulphur by a few light taps. This, M. Planté thinks, may explain the plant-like impressions some-times found on the bodies of persons struck by lightning. But little dynamic electricity is required for these and other static effects described (that from 3 or 4 Daniell elements). By associating all the condensers in surface, and adding a small special rotating commutator, static effects of quantity are had, different from those of tension. By mechanical force of successive sparks M. Plante elevates water.—On the treatment by submersion of vines attacked by phylloxera, by M. Faucon. Some of the insects always survive.—On the phylloxera in the Côte d'Or, by M. Viallane.—On the treatment of anthracnose; observations of M. Puel, by M. Portes. The efficacy of lime is demonstrated.—Observations at Marseilles Observatory, by M. Stephan.—On a definite integral, by M. Callandreau.—On the integration of equations with partial derivatives of orders superior to the first, by M. Pellet.—Minimum of dispersion of prisms; achromatism of two lenses of the same substance, by M. Thollon. Two lenses of the same substance, traversed, the one at the minimum of dispersion, the other at the minimum of deviation, by a luminous beam, may at once deflect and achromatise the light. Hence a system of lenses of the same matter may be made, having one focus and at the same time being achromatic.—On the vapour of bisulphydrate of ammonia, by M. Isambert.—On the dissolution of carbonic oxide in acid protochloride of copper, by M. Hammerl. A thermo-chemical investigation.—On the transformation of tartaric acid into glyceric and pyruvic acids, by M, Bouchardat.—On the isomerism of borneol, by M. De Montgolfier.—On bichlorhydrate of turpentine, by the same.—On some derivatives of indigotine, by M. Giraud.—Comparison of effects of inhalations of chloroform and ether, in anæsthetic and in toxical dose, on the heart and the respiration; applications, by M. Arloing. In the first phase attention should be given both to the heart and the respiration, whether chloroform or ether be used; in the second, the heart must be watched, and especially in the case of chloroform; in the third, the respiration. Chloroform should be preferred to ether, where the operation may be long, as the denouement of intoxication by ether is more sudden.—Causes of death from intravenous injection of milk and sugar, by MM. Moutard-Martin and Richet. Death from injection of a great quantity of milk is the result of bulbar anaemia, which produces phenomena of excitation.—On the reproduction of Amblystomas at the Museum of Natural History, by M. Vaillanto—Comparative anatomy of the Hirudineæ; organisation of the Batracobdella latasti, C, Vig., by M. Vignier.