Oct ly, 1878] 



NATURE 



^57 



Table of Free Lines in Angstr'dnCs Solar Spectnim which may be 

 attrihiled to Oxygen. 



Angstrom's solar 

 spectrum. 



4133-202 

 4155-802 



4254-55^* 

 4303-002 

 4316-502 

 4347-95' 



4394*45' 

 4595-202 



4648-75* 

 4661-702 



The subjects presented in this communication may be briefly 

 summed up as follows : — 



1. The resort to the process of reflection in producing and 

 photographing solar spectra, and thereby avoiding certain errors, 

 and the employment of the silvered surface itself of a glass 

 gi-ating. 



2. The extension of the measurement of oxygen lines into the 

 ultra-violet region. 



3. The measurement in the region of less refrangibility than 

 H, of lines of oxygen not heretofore recorded, and the use of 

 projection as a method of measurement. 



4. The establishment of a close relationship in position 

 between certain lines in the solar spectrum and the lines of 

 oxygen; the slight difi-erences that exist being assignable to 

 the experimental difficulties in the way of making accurate 

 measures of the oxygen lines, and falling within the limits of 

 error of experiment. 



5. The evolution of the fact that the lines of the solar spec- 

 trum which appear to correspond to the lines of oxygen are 

 weak, or faint, and show that that gas possesses a feeble ab- 

 sorbent power when compared with metallic vapours or gases 

 like H, Fe, Ca, 



6. The demonstration that in Angstrom's chart there are 

 many lines not assignable to any elementary body, and that 

 these lines occupy very closely the positions of certain oxygen 

 lines. 



7. The suggestion that the proof of the presence in the solar 

 envelopes of oxygen, and other substances giving faint lines, 

 is a problem not to be solved by the comparison of two spectra 

 of small dispersion. The solar spectrum in certain parts is so 

 crowded with lines presenting all kinds of details, that the only 

 satisfactory Avay is to make measures of the positions of these 

 lines on a large scale, and as truly as possible, and then compare 

 with these the most accurate measures of oxygen lines that can 

 be made. 



CYON'S RESEARCHES ON THE EAR i 



II. 



TTAVING now described, at what we hope our readers will not 

 ■*■ ■*■ _ consider inordinate length, the history of the subject up to 

 the time when Dr. de Cyon commenced his second series of ex- 

 periments, a history_ which he gives in the first part of his thesis 

 in a very clear and impartial manner, we shall now give a short 

 account of the new matter contained in the second part. This 

 may be arranged under two heads — (i) experiments undertaken 

 chiefly with the view of testing the kinetic theory, and (2) the 

 statement of his own theory and arguments in support of it. 



The experiments have obviously been made with exti-aordinary 

 care and skill. Dr. de Cyon succeeded in producing the lesions 

 which he intended to produce, without injuring any other part, 

 and in most cases with scarcely any loss of blood ; we can thus 

 observe the eff-ects of any particular operation without the 

 slightest complication from concurrent injuryror inflammation of 

 the cerebellum. He has established in the most convincing way, 

 (i) the fact observed by Flourens that the movements of the 

 head always take place " in the plane of the divided canal," or, 



' Recherches exp^rimentales sur les Fonctions des Canaux semi-circu- 

 laires et sur leur Role dans la Formation de la Notion de I'Espace. Par Elie 

 de Cyon, M.D., &c., Laureat de I'Institut de France. Continued from p. 

 635- , 



as we should express it, about an axis at right angles [to that 

 plane. (2) That the movements are much more violent, and 

 that the loss of equilibrium is much more persistent, when the 

 coiTesponding canals of both sides are cut, than when one only, 

 or two dissimilar canals are divided. (3) That when all six 

 canals are destroyed very violent and complex convulsions occur 

 and continue for several days. If the animal survive this stage 

 it gradually attains a condition in which its movements are 

 eff-ected with great deliberation, and in which the sense of sight 

 is absolutely necessary to enable it to direct itself. These ex- 

 periments were made upon pigeons, upon rabbits, and upon 

 lampreys, the latter animals being especially interesting as pos- 

 sessing only four canals, two on each side. 



So far, the results of the new experiments confirm and render 

 more precise the knowledge derived from previous investio-a- 

 tions, and they are in perfect accordance with the kinetic theory. 

 One point, however, requires special notice. 



Dr. de Cyon points out that the first movement made by an 

 animal on the section of a canal, takes place in a direction " from 

 the divided canal." It is not quite easy to make out the precise 

 meaning of this phrase. It may, and probably does mean, that 

 when the left horizontal canal is cut the pigeon moves its beak 

 to the right ; but, as the operator is at the back of the bird, it 

 may also mean that the back of the head moves to the right and 

 away from the divided canal. Judging, however, from the ex- 

 periments upon the vertical canals, it is most probable that Dr. 

 de Cyon means that the first movement takes place in such a 

 manner that the ampulla of the divided canal precedes the canal. 

 If this be the case, and if, as seems reasonable, we assume that 

 the first eff"ect of the division is stimulation and not paralysis, 

 and that the movement is a compensatory one— that is, the 

 result of an effort to preserve the same position — we are forced 

 to the conclusion that the canal is affected by a rotation in which 

 the ampulla follows the canal, contrary to the view somewhat 

 hesitatingly expressed by Brown and Mach. 



Dr. de Cyon has, however, made several experiments, the 

 results of which cannot so easily be harmonised with the kinetic 

 theory. These experiments were made expressly to test the 

 truth of this theory, and in his opinion their results render it 

 untenable. As Mach holds that change of pressure in the 

 ampullae excites the ampullary nerves and produces a sensation 

 of rotation, Dr. de Cyon devised and executed a series of ex- 

 periments so arranged that the pressure in the ampuUse should 

 be changed, without injury to the membranoXis canals, i. He 

 opened the bony canal and allowed the perilymph to escape. 

 2. He opened the utricle and allowed the endolymph to 

 escape, and observed that the whole membranous labyrinth 

 collapsed. 3. He introduced into the space containing the 

 perilymph small rods of dried laminaria ; these rods slowly 

 swelled by imbibing moisture, and must have considerably in- 

 creased the pressure in the interior of the cavity. In none 

 of these cases did he observe any trace of the Flourens phe- 

 nomena. 4. He replaced the periljrmph by a lukewarm solu- 

 tion of gelatine, which solidified, and inclosed the mem- 

 branous labyrinth in an approximately rigid case. Still no 

 Flourens phenomena were observed, but these at once occurred 

 on pricking the membranous canals through the solid gelatine. 



Dr. de Cyon further mentions as an argument against Mach's 

 view, the fact that periodic changes of pressure occm: in the 

 contents of the labyrinth, synchronous with the heart's beat, 

 and evidently connected with the change of arterial pressure. 

 This, he thinks should, on Mach's hypothesis, produce irritation 

 of the nerves and sensation. It must, however, be observed, 

 that this change of pressure is produced simultaneously in all the 

 six ampullae, and that therefore the resultant rotation perceived 

 would be zero. 



But by far the most important evidence in opposition to the 

 kinetic theory is derived from the section of the whole auditory 

 nerve. Dr. de Cyon succeeded in performing this operation 

 without serious injury to any other part, and found that rabbits, 

 in which both of the auditory nerves had been divided, and in 

 which, therefore, all nervous connection between the semi- 

 circular canals and the brain had been cut off, showed, after 

 being subjected to rotation, the same symptoms of vertigo 

 observed by Mach in the case of normal rabbits. It is unfor- 

 tunate that Dr. de Cyon has not given further details of this most 

 important experiment. 



External irritations which, when small, are perceived only by 

 the organs specially fitted for their perception, as a rule act, 

 when very intense, upon other organs. Thus a feeble sound can 



