26o 



NA TURE 



[July 13. 1893 



Bouty and Foussereau failed altogether to obtain consistent 

 results, these- may be secured by using certain precautions, such 

 as placing the induction coil at a sufficient distance ( i m. at least) 

 from the bridge, directing its axis perpendicular to that of the 

 rheostat, and placing the telephone perpendicular to the lines 

 of force of the induction coil. In the case of water and very 

 dilute solutions the electrostatic capacity of the containing cell 

 is a source of disturbance, which may, hew ver, be obliterated 

 by introducing a small condenser of adjustable capacity. — The 

 temperature coefficient of the dielectric constant of pure water, 

 by F. Heerwagen. This was investigated with a kind of differ- 

 ential electrometer, in which two needles were suspended by 

 one wire in two electrometers arranged vertically one above the 

 other. The needles, the vessel, and one pair each of the 

 quadrants were joined to one point in a constant voltaic circuit, 

 and the other pairs to two other points. The lower electro- 

 meter was alternately empty and filled with pure water. Under 

 these circumstances the ratio of the sensibilities was inversely as 

 the ratio of the squares of the differences of potential. The 

 value obtained for K was 80-878 - 0-362 (/ - 17), where t is 

 the temperature of the water in degrees centigrade. — Polarising 

 effects of the refraction of light, by K. Exner. Glass gratings, 

 necessary in order to obtain a sufficiently large angle of diffrac- 

 tion, have the disadvantage of producing polarisation effects 

 due to change of medium in addition to those due to diffrac- 

 tion. This difficulty was overcome by attaching the cut sui face 

 to a semi-cylinirical lens by a drop of oil of the same refractive 

 index. The polarisation effects show a fair agreement with 

 Stokes's cosine Uw. 



SOCIETIES AND ACADEMIES. 



London. 



Royal Society, June 8. — " The Process of Secretion in 

 the Skin of the Common Eel," by E. Waymouth Rcid, Pro- 

 fessor of Physiology in University College, Dundee. 



By special attention to the condition of the fish at the time of 

 fixation of their skins for histological investigation, the author 

 has succeeded in obtaining pictures of the various phases of 

 secretory action. The lowest phase of activity was obtained by 

 rendering hybernating fish suddenly motionless by a successful 

 transfixion of the medulla, and then removing skin before re- 

 covery from "shock" admitted of reflex secretion. T^ie highest 

 phase of secretory action was produced by artificial stimulation 

 of the intact animal by the vapour of chloroform, by faradisa- 

 tion, or by simply allowing a pithed summer eel to "slime " 

 after recovery from the primary "shock." The following are 

 the main conclusions : — 



(1) The secreting elements of the epidermis of the common 

 eel consist of goblet cells and club cells, both direct descend- 

 ants of the cells of the palisade layer. The former supply a 

 mucin, the latter threads and a material appearing as fine 

 granules in the slime. 



(2) The goblet cells contain mucin granules, and, after reach- 

 ing the surface and discharging their load, are capable of 

 undergoing regeneration by growth of the protoplasmic foot and 

 re-formation of mucin. 



(3) The threads of the slime resemble those of Myxine 

 glutinosa, but are usually of finer texture. As in Myxine, they 

 are developed from the club cells, but there are no special 

 glandular involutions of the epidermis. The club cells of 

 Petromyzon fluviatilis also supply slime threads. 



(4) The granular material of the slime is the contents of 

 vesicular spaces developed in the club cells in the immediate 

 neighbourhood of their nuclei, and is set free enclosed in a 

 lattice work developed by vacuolation of the surrounding 

 material, and finally extruded, carrying with it the original 

 nucleus of the club cell. 



(5) The remainder of the club cell, after extrusion of its 

 vesicle and nucleus, becomes a spirally coiled fibre, which 

 finally breaks up into the fine fibrils of the slime. 



(6) Severe stimulation, especially by the vapour of chloroform 

 applied to the intact animal, causes so sudden a development 

 of the coiled fibres from the club cells that the surface of the 

 epidermis is thrown off and the secretory products set free en 

 masse. This process is of reflex nature, for similar excitation 

 applied to excised skin is without effect. 



(7) A system of connective tissue cells, distinct from chroma- 

 tophores, exists in the epidermis developed from cells which are 



NO. 1237, VOL. 48] 



direct descendants of leucocytes, and which can be traced from 

 the blood vessels of the corium through the basement mem- 

 brane into the epideimis. The number of these wandering 

 cells in the epidermis is greatly increased by stimulation, pro- 

 bably with a view to providing subsequent support to the 

 secretory elements during regeneration. 



The paper was illustrated by photo-micrographic lantern 

 slides. 



June 15.— "On the Ratio of the Specific Heats of the 

 Paraffins and their Monohalogen Derivatives." By J. VV. 

 Capstick, D.Sc. (Vict.), B.A. (Camb.), Scholar and Coutts- 

 Trotter Student of Trinity College, Cambridge. Communicated 

 by Prof. J. J. Thomson, F.R.S. 



The object of the experiments was to throw light on an ob- 

 scure point in the kinetic theory of gases, viz. the distribution 

 of energy in the molecule. 



From the ratio of the specific heats we can calculate the rela- 

 tive rates of increase of the internal energy and the energy of 

 translation of the molecules per degree rise of temperature, by 



the well-known formula, /3 -f l = 



where 7 is the ratio 



3(7 - J)' 



of the specific heats and /3 the ratio of the rate of increase of the 

 internal to that of the translational energy. 



In order to make the results comparable it was decided to 

 keep the translational energy constant by working at a constant 

 temperature — the temperature of the room. 



The ratio of the specific heats was calculated from the 

 velocity of sound in the gases. This was determined by 

 Kundt's method, a double-ended form of apparatus similar to 

 that described in Pogg. Ann. vol. cxxxv. being used. 



The calculation requires the density of the gas to be known, 

 a circumstance which makes the method very sensitive to small 

 amounts of impurity. Regnault's value of the density was used 

 for methane and the theoretical value for ethane, an analysis of 

 the gas being made after each experiment to determine the cor- 

 rection for the air that was unavoidably present. AH the oiher 

 gases were freed from air by liquefaction immediately before 

 being admitted into the apparatus, and the vapour density of 

 the material in the state in which it was used was determined 

 by a modified form of Hofmann's apparatus, which gave results 

 concordant to one part in a thousand. 



The formula used in calculating the ratio of the specific heats 

 was 



, = l-408xpxg,J(l + i|(/.)). 



the last factor being added to the ordinary formula to correct for 

 the divergence of the gas from Boyle's Law. 



The correction is obtained at once by putting in the equation 



u' = - yv 



('-2 1 the value of (-f), given by the equation 

 \dv/t \d-vj 



-p + v\ 



\dv), 



fdfv\ 



\avji 



From the vapour density determinations a curve is con- 

 structed giving pv in terms of z\ and the slope of this curve 



at any point gives the value of Ap'^') in arbitrary units. Divid- 

 ing by the corresponding value oi p in the same units, we obtain 

 the amount of the correction. 



The correction increases the ratio of the specific heats by from 

 I to 2 per cent, in most cases. 



Observations varying in number from three to nine were 

 made on each gas, the extreme range of the values being 2 per 

 cent, for marsh gas, 14 per cent, for methyl iodide, and I per 

 cent. , or less, for the rest. 



The mean values of the ratio of the specific heats are shown 

 in the following table : — 



Methane 



Methyl chloride 



Methyl bromide 



Methyl iodide 



Ethane 



Ethyl chloride 



Ethyl bromide 



Propane 



Normal propyl chloride 

 Isopropyl chloride 

 Isopropyl bromide 



