JULV II, 1895] 



NATURE 



26- 



manner in which two or more simple mechanisms are associated 

 together, and the compound mechanism built up. 



June 20. — "The Influence of the Cerebral Cortex on the 

 Larynx." By Dr. J. S. Kisien Russell. 



The author found the condition of the peripheral laryngeal 

 apparatus has practically no effect on the result obtained from 

 the central nervous mechanism, for abduction or adduction of 

 the vocal cords resulted on excitation of the appropriate area of 

 the cerebral cortex, irrespective of whether abduction or adduc- 

 tion was obtained on excitation of the recurrent laryngeal nerves 

 iq the same animal. No evidence of unilateral representation 

 of the movements of the vocal cords in the cerebral cortex w-as 

 obtained, although this point was tested in various ways. Nor 

 was it found possible l»-» inhibit the abductor muscles by excita- 

 tion of the cortical centre of their antagonists the adductors. 

 It was founil that both in the dog and cat there existed a focus, 

 excitation of which resulted in .idduction of the vocal cords, and 

 another near to this, stimulation of which resulted in alxluction 

 of the cords. While in the cat it was possible to differentiate 

 these movements without any preliminary measures being 

 adopted, it was only after the adductor fibres of one recurrent 

 lary'ngeal nerve had been divided transversely that it first became 

 possible to evoke abduction of tl-.e vocal cords on excitation of 

 the cortex, th<)Ugh in subsequent experiments it was sometimes 

 possible to evoke this movemen* on excitation of the cortex of 

 the dng without adopting this preliminary measure. The other 

 effect on the cords, which it was as a rule found most nifficult to 

 differentiate from that of abduction, was acceleration of their 

 movements. It was further found that on the anterior composite 

 gyrus, below the abductor centre, there existed a focus, excitation 

 of which resulted in a clonic adductor effect on the cords, in 

 which the cords were first brought into a position of moderate 

 adduction, and then there was added rapid short to-and-fro ex- 

 cursions. On passing within the confines of Spencer's area for 

 arrest of respiration, it was found that in the peripheral parts of 

 this area there existed three foci, excitation of which affected the 

 cords in different ways. The most anterior was responsible for 

 arrest of the cords in adduction, i.e. in the expiratory' stage of 

 their excursions ; excitation of the focus behind this, and corre- 

 sponding, jjrobably, to Horsley and .Semon's abductor centre 

 in the cat, was followed by arrest of the cords in abduc- 

 tion, i.e. their inspiratory position ; while the most posterior 

 focus, which is situated at about the junction of the 

 anterior composite and anterior sylvian convolutions, resulted 

 in intensification combined with acceleration of the movements 

 of the cords when stimulated. Excitation of Spencer's chief 

 focus for arrest of respiration on the olfactory lobe, resulted 

 in arrest of the cords in the position they occujjy during 

 expiration in the dog, .ind in the position they occupy during 

 inspiration in the cat. 



Physical Society, June 28. — Dr. dladstone, \'ice-Presidenl, 

 in the chair. — Mr. Howden read a note on an electro-magnetic 

 effect. .\ long glass tube containing mercury, and fitted with a 

 small stand-jjipc to indicate hydrostatic pressure, is pa.ssed be- 

 tween the poles of an electro-magnet. On passing a current of 

 about 30 amperes through the mercury in this tube, the stand- 

 pipe being turned so as to indicate the pressure either per- 

 pendicular or parallel to the lines of force of the field of the 

 electro-magnet, movements of the mercury in the stand-pipe 

 take place. When the stand-|)ipe is perpendicular to the lines 

 of force of the field, the mercury rises or falls according to the 

 direction of the current. When the stand-pipe, however, is 

 parallel to the lines of force, the mercury always rises, whatever 

 the direction of the current. I'rof. S. 1'. Thompscm .said there 

 appeared to be three unexplained efi'ects, one proportional to 

 the current and the field, and reversible ; another, indepen- 

 dent of the direction of the cmrent, or of the field; and 

 a third, which only occurred while the current was changing 

 in strength. In addition there may be a fourth effect, which 

 up to now has not been noticetl. The motion of the mercury 

 column in I'ig. I of the paper was in the opposite direction to 

 that of the drag on a conductor carrying the current. An 

 ii|i].arenl rise in pressiue might be due to a decre.-ise in the 

 density of the mercury due lo the heat developed by the 

 current. Mr. Blakesley asked ii the author had noticed any 

 changes in level in the mercury reservoirs at the ends of the 

 lube. The author, in his reply, said the reservoirs at the ends 

 were so large that no changes of level were appreciable. — Mr. 

 Rhodes read a paper on the armature reaction in a single i^hase 



NO. 1 34 1, VOL. 52] 



alternating current machine. In this paper the author gives the 

 investigations that were the subject of a verbal addendum to a 

 paper read before the Society orv a previous occasion. He inves- 

 tigates the lag or lead of the K.M.F.s over the current, and 

 applies the results to examine whether the field excitation of the 

 generator or the motor is strengthened or weakened by the re- 

 action of the armature currents. Mr. Tunzelmann expressed a 

 hope that the .author would amplify parts of his paper. Mr. 

 Hlakesley said the conclusion of the author that " either of two 

 alternate current machines may be driven as a motor by the 

 other, irrespective of their relative E. M.F.s," is not invariably 

 correct. The facts of the case were these : the E. M.E. of the 

 motor may exceed that of the other machine to a certain extent ; 

 but that E.M.E., multiplied by the cosine of the angle of 

 electric lag, must yield a product not greater than the E..M.F. 

 of the generator ; i.e. using Mr. Rhodes' symbols e cos 9 must 

 not be greater than E. Mr. Blakesley gave a geometrical proof 

 of this, but the same proposition had been given by him some 

 ten years ago in the course of investigating the subject generally. 

 This was at a time when Dr. John Hopkinson was, with less, 

 than his usual ]iersi)icuity, leaching that synchronous alternate 

 current machines could not be run in series with stability, both 

 doing work. Referring to the author's diagrams, Mr. Blakesley 

 said that in a jiroblem involving so many elements as that under 

 consideration, it was impossible with the limited dimensions of 

 space to represent the results with the complete generality of a 

 formula. Some elements had to be taken as the independent, 

 others as the dependent variables. The author had considered 

 the power transmitted to the motor, the E. M.F. of the generator 

 and the angle of electric lag as independent. The E. M. F". of the 

 motor was dependent. In Mr. Blakesley's original diagrams the 

 E. M.F.s were both considered independent as well as the 

 electric lag, and the powers applied or transmitted as dependent 

 variables. In any case the formuk-e properly derived fron. such 

 diagrams became perfectly general, and it did not ajipear to him 

 that the change of method indicated could properly be called a 

 new theory on the subject. As a matter of fact, diagrams based 

 on the independence of the E. M.F.s and the electric lag would 

 furnish a better means of discussing the question of the stability 

 of the motion than Mr. Rhodes' plan, and this might account 

 for the entire omission from the paper of this important matter. 

 I'rof. S. 1'. Thompson said it was imjiossible to discuss the 

 question of stability till the subject of armature reaction had been 

 thoroughly investigated. The terms lag and lead had been used 

 by Mr. Rhodes in a consistent manner; but this was not always 

 done, and he reconnnended that the phase of the current which 

 was common to both generator and motor be taken as the 

 standard. The author, in his reply, said he agreed with Mr. 

 Hlakesley that there was a limit to the extent lo which the 

 motor might be excited, and this upper limit could easily be 

 obtained from the figure given in the paper. The queslicm of 

 armature reaction was, however, most important, as it might 

 excite the field two or three times more than the original excita- 

 tion. Since motors were designed to do a certain amount of work, 

 and not the work to fit the motor, it w-as most natural to take the 

 output of the motor as fixed. — Mr. Shelford Bidwell read a 

 pajier on the electrical properties of selenium. The author h.as 

 continued his investigations on this subject, and has come to the 

 following conclusions : ( i ) The conductivit)- of crystalline Se 

 appears to depend princii»lly on the impurities which it con- 

 tains in the form of metallic selenides. It may be that the 

 selenides conduct electrolytically, and that the influence of light 

 in increasing the conductivity is to be attributed to its proi^rty 

 of facilitating the combination of Se with metals in contact with 

 it. (2) A Se cell having platinum electrodes, and made with 

 Se to which about 3 per cent, of cuprous selenide has been 

 added is, even tho\igh unannealed, greatly superior both in 

 conductivity and sensitiveness lo a similar cell made with 

 ordinary Se and annealed for several hours. (3) Red Se in 

 cont.act with cojiper or brass, is quickly darkened by the action 

 of light, owing, it is suggested, lo the formation of a selenide. 

 (4) Crystalline Se is porous and absorbs moisture from the air, 

 and it is this moisture that causes the polarisation of Se after 

 the passage of a current. (5) The presence of moisture is not 

 essential to sensiti\ eness, but appears to be in a slight degree 

 favourable to il. (6) If cuprous selenide is made the kathotle 

 in an electrolytic cell, and a strip of platinum the anode in 

 water, red Se mixed with detached particles of the selenide is 

 deposited in the waler. (7) The photo-electric currents some- 

 times set up when light falls upon Se, are dependent upon the 



