May 4, 1876J 



NATURE 



15 



over a solution of iodide of potassium. By means of the 

 air pump it is easy with a gentle exhaustion to expand 

 the gas so that it may fill the whole tube while the open 

 end is immersed in the liquid which it is desired to intro- 

 duce ; on removing the pressure the gas will be in contact 

 with the new liquid. 



The lecturer exhibited some of the original tubes with 

 which Prof. Tait and he first determined that ozone is a 

 condensed form of oxygen, and explained a form of appa- 

 ratus by means of which this important fact can be exhi- 

 bited as a class experiment. A full description of this 

 I apparatus will be found in his lecture on ozone, which 

 was delivered some time ago before the Royal Society of 

 Edinburgh, and has since been published by the Scottish 

 Meteorological Society. With this apparatus the lecturer 

 has been able to determine that chlorine gas undergoes 

 no change of volume from the prolonged action of the 

 electrical discharge. His experiments on this subject 

 have not yet been pubhshed, but they were made under 

 singularly favourable conditions for discovering a very 

 small change of volume in the gas if any such change had 

 occurred. 



The lecturer in the next place briefly alluded to the 

 method he formerly employed for determining the latent 

 heat of vapours of which a detailed account was given in 

 a former communication to the Chemical Society. The 

 apparatus employed admits of exact experiments being 

 made on a small scale, and consequently on substances 

 in an absolutely pure state, an object of even greater im- 

 portance in inquiries of this kind than in ordinary 

 chemical analyses. He remarked that a large field for 

 investigation in this part of the domain of science lay 

 comparatively uncultivated and would yield a rich harvest 

 of results to anyone who would enter upon it. 



Passing from this subject, the lecturer described a 

 dividing and calibrating machine which he contrived 

 some years ago for the special work in which he has been 

 engaged, and which has given to many of his investiga- 

 tions an accuracy otherwise hardly attainable. He has 

 been enabled by means of it to construct thermometers 

 whose readings are absolutely coincident throughout every 

 part of the scale, and to calibrate with almost perfect 

 accuracy the glass tubes used in his pressure experiments. 

 It would be impossible in an abstract to describe the con- 

 struction of this machine, but it may be important to 

 mention that the screw which moves the microscope or 

 divider is a short one of remarkable accuracy constructed 

 by Troughton and Simms. 



The last subject treated was the lecturer's method of 

 invesfigating the properties of gaseous and liquid bodies 

 at high pressures and under varied temperatures. By 

 means of his apparatus, which was exhibited to the 

 meeting, pressures of 500 atmospheres can be readily 

 observed and measured in glass tubes — in a word, a com- 

 plete mastery obtained over matter under conditions 

 hitherto beyond the reach of direct observations. This 

 has been effected by a novel mode of packing a fine steel 

 screw, so that while entering a confined portion of water 

 no leakage whatever occurs under enormous pressures, 

 and also by a peculiar method of forming a tight junction 

 between glass and metal. The lecture was concluded by 

 a short statement of the more important results lately 

 communicated to the Royal Society on the properties of 

 matter in the gaseous state, 



SCIENCE IN GERMANY 

 {From a German Correspondent.) 



IN my last communication (Nature, vol. xiii, p. 75), 

 I noticed the researches of Ranke on various organs 

 of sense of the lower animals. A new series of these 

 researches having since appeared, I will give some 

 account of them in what follows. Ranke {Zeitschrift fiir 

 Wissenschaftliche Zoologie, xxv., 2 Heft. Supplement.) has 



studied more closely, in their physiological relations, the 

 organ of hearing of certain grasshoppers {Acridia) and 

 snails {Pteroirachea), and the eye of the leech, which organs 

 were previously known in general from the researches of 

 Siebold, Leuckart, Leydig, Boll, and others. The Acridia 

 carry their organ of hearing on the base of the hinder- 

 most extremity. It consists essentially of a membrane, 

 which is stretched within the body wall on a fixed ring, 

 and an auditory nerve, which is connected from within 

 to that membrane, and ends on it in a swelling or so- 

 called ganglion. That membrane is undoubtedly to be 

 compared with the membrane of the tympanum in the ear 

 of the most highly organised animals ; inasmuch as, like 

 this, it is put in vibrations corresponding to the sound- 

 waves in the air, and transfers these vibrations to the parts 

 lying within. In the higher animals, these parts consist 

 of rigid lever arrangements (small bones of the ear), 

 which, however, are connected with the acoustic nerve 

 not directly, but through a transmitting apparatus, which 

 separates the vibrations produced by various sound-waves, 

 and specially prepares them for conveyance by the nerves. 

 In the Acridia, the whole internal conduction of the 

 sound-waves is more simply arranged ; the ganglion on 

 the tympanic membrane consists of two different halves ; 

 in the interior the finest nerve-threads proceeding from 

 the auditory nerve unite with large round nerve-cells, from 



B 



I 



Ganglion of organ of hearing in 

 Acridia (schema after Ranke). 



Eye of leech (schema after 

 Ranke). 



which they proceed to the boundary of this half of the 

 ganglion, and there end in smaller nerve-cdls. The outer 

 half of the ganglion consists of a brighter and delicate 

 ground mass, in which very fine rods, transparent like 

 glass, and fixed, run parallel towards the tympanic mem- 

 brane ; they spring out of those smaller cells, terminate 

 on the tympanic membrane with longish thickenings, and 

 may be regarded as the end-apparatus of the nerve-con- 

 duction. But while thus the vibrations of the tympanic 

 membrane are communicated to the rods and from these 

 direct, without further intervention, to the nerve-appa- 

 ratus, there is not entirely wanting a weakening or 

 damping arrangement for the sound-waves ; for the 

 ground-mass, in which the rods rest, may very well be 

 regarded as such an arrangement. As the rods are all 

 formed alike, the sensations of tone by the Acridia must 

 be always homogeneous and simple ; and if we may 

 suppose that the organ of hearing of these animals is 

 adapted to their own production of tone, by which they 

 excite sexual desire, then their monotonous rattle agrees 

 with the arrangement of the auditory apparatus for a 

 simple sensation. In other grasshoppers, the Locustida, 

 the vocal organ produces a sound compounded of more 

 tones ; and correspondingly, they have on their fore legs 

 an organ of hearing, the rods in which are of various 

 length and breadth, and, arranged like the wires in a 



