Oct. lo, 1878] 



NATURE 



635 



rotational movement of the whole system (that is, of the head) 

 currents of liquid in a direction opposite to that in which the 

 head is turned. The amount of the flow in each canal depends 

 upon the plane in which the head is turned and upon th^ rate 

 of the rotation. There are perfectly fixed relations between the 

 rotational movement of the head and the currents in the inclosed 

 liquid ; if these currents can be perceivred they will give us an 

 exact account of the rotational movement of the head. We may 

 regard, as possible organs for the perception of the currents, the 

 so-called ' auditory hairs ' which project at right angles inwards 

 from a widened and flattened part of the canal ; they are thus 

 placed so as to be most sensitive to currents in the canal, and 

 are on the other hand connected to nerves, of which they form 

 the end-organs. 



" To turn these facts to account in the sense of Goltz's theory 

 we must assume that every flow of the endolymph, perceived by 

 the ampullary nerves, produces a sensation of rotation of the 

 head in the plane of the canal in which the flow takes place, 

 and in a direction opposite to it, but that the perceptions of the 

 six ampullae of the two labyrinths combine to form a joint 

 sensation 



' ' Our assumption has a necessary consequence. If the rota- 

 tion of the head (of course along with the body) is kept up, the 

 initial backward flow of the endolymph will be destroyed by 

 friction against the walls. If the head then suddenly stops, the 

 endolymph must, in virtue of its inertia, flow on in the sense of 

 the rotation of the head ; a sensation will therefore be produced 

 of rotation of the head and body in a direction opposed to that 

 of the previous rotation." 



In this view the endoljonph is held to lag behind the ro- 

 tational movement of the head when this movement begins; — when 

 the movement has continued at a uniform rate for some time, 

 the endolymph is constrained, by fluid friction, to take part in 

 the movement of the head, and if then the rotation of the head 

 stops, the endolymph moves on. We have, thus, two ways in 

 which a relative motion can occur between the endolymph and 

 the walls of the cavity containing it : — i. When the head begins 

 to move — here the waUs leave the fluid behind. 2. When the 

 head stops — ^here the fluid flows on. In both cases the sensa- 

 tion of rotation is felt. In the first this sensation corresponds 

 to a real rotation, in the second it does not, but in both it corre- 

 sponds to a real acceleration (positive or negative) of rotation, 

 using the word acceleration in its technical kinematical sense. 



Mach's view differs fi:om Breuer's in this, that while Breuer 

 assumes an actual flow of endolymph through the canals, Mach 

 believes that the very narrow bore of the canals will preclude 

 such a flow — the friction being so great that the most abrupt 

 rotational movement of the head will not produce sufficient 

 difierence of pressure to cause an actual current. Instead of a 

 current there will be produced a change of pressure in the 

 ampulla, which would produce a current were the canal wider, 

 and this change of pressure may be sufficient to act on the hair- 

 cells, and irritate the ends of the nerves. 



In Brown's statement of the theory, not the endolymph only, 

 but the whole liquid and soft contents of the bony canals are 

 supposed to lag behind the movement of the head, and in his first 

 paper he suggested that there might be a relative motion between 

 the bony and the membranous canals. This view, founded on the 

 statement to be found in various anatomical text-books, that the 

 membranous canals float nearly loose in the bony canals, is 

 scarcely tenable when we know that the former are somewhat 

 firmly attached at one side to the periosteum. 



Another important point in which Brown's statement of the 

 theory differs from that of Mach and from that of Breuer, lies 

 in his regarding the two labyrinths as forming one organ, all the 

 six canals of which are required to form a true conception of 

 the rotatory motion of the head. 



The doctrine of specific nervous action, now we beUeve gene- 

 rally accepted by physiologists, implies that while greater or less 

 stimulation of an end-orjgan produces difference of sensation, a 

 variety in the mode of stimulation cannot be perceived. Flow 

 through the ampulla from the utricle to the canal on the one 

 one hand, and from the canal to the utricle on the other, must 

 produce a precisely similar sensation if the hairs of the hair-cells 

 are equally moved. We must therefore look further for an 

 explanation of our power of distinguishing between rotation in 

 the one sense and rotation in the other sense about the same 

 axis. 



Mach was at first inclined to suppose that in each ampulla 

 there are two sets of nerves each sensible to rotation in one sense 



only. He now adopts the explanation proposed by Brown, who 

 based it upon the fact established by careful measurements 

 in a considerable number of animals, that the six canals are 

 sensibly parallel two and two. Thus the two horizontal canals 

 are in the same plane, while the superior canal of one side is in a 

 plane nearly parallel to that of the posterior canal of the other side. 

 Further, in each of these three pairs (right and left horizontal, 

 right superior and left posterior, right posterior and left superior), 

 the two canals are so placed that when rotation takes place about 

 the axis to which they are perpendicular, one of the two canals 

 moves with its ampulla preceding the canal, so that the flow, or 

 tendency to flow, is from ampulla to canal, while in the other the 

 ampulla follows the canal and the flow, or tendency to flow, is from 

 canal to ampulla. If, then, we suppose that flow from ampulla to 

 canal — or, adopting Mach's view as stated above, increase oi pres- 

 sure in the ampulla — alone stimulates the hair-cells, while no effect 

 is produced by flow in the opposite direction — or by diminution of 

 pressure in the ampulla — we have in the six canals a mechanical 

 system capable of giving us an accurate notion of the axis 

 about which rotation of the head takes place, and of the sense 

 of the rotation. To this explanation Dr. de Cyon objects that 

 it assumes two organs, the superior canal of one side, and the 

 posterior canal of the other side, which are not anatomically 

 fellows, to be physiologically fellows. To this it is sufficient to 

 answer that the motions which these two organs are supposed to 

 perceive are produced by altogether different muscles. Let us 

 take the case of the right superior and left posterior canal — the 

 former is sensitive to rotation in one sense about an axis approxi- 

 mately passing through the left eye and the right mastoid 

 process, a motion produced by muscles on the right side of the 

 front of the neck, while the latter canal is sensitive to exactly the 

 contrary motion about the same axis, and this motion is pro- 

 duced by muscles on the left side of the back of the neck. It is 

 surely unreasonable to expect anatomical relations to exist 

 between the organs perceiving two motions which do not exist 

 between those producing them. 



Alex. Crum Brown 

 {To be cofiiinued.) 



UNIVERSITY AND EDUCATIONAL 

 INTELLIGENCE 



We have already referred to the mathematical courses for 

 session 1878-9 in Johns Hopkins University, Baltimore. The 

 following is the detailed programme : — I. Prof. Sylvester will 

 lecttire on (a) determinants, (b) modern algebra, (c) theory of 

 numbers. II. Dr. Story will lecture on {a) higher plane curves, 

 {b) solid analytic geometry, {c) quaternions, {d) elliptic functions. 

 III. Mr. Craig will lecture on hydrodynamics. IV. Lectures 

 will be given by appointed instructors on {a) differential equa- 

 tions, {b) analytic mechanics, [c) conic sections, (d) theory of 

 equations, (if) differential and integral calculu?. V. Mathe- 

 matical Seminarium : — A Mathematical Seminarium is con- 

 ducted under the guidance of the Professor and Dr. Story ; it 

 comprises all the instructors and students of mathematics in the 

 university. At its monthly meetings, besides occasional papers, 

 such topics as may from time to time suggest themselves in the 

 course of reading to the students or instructors, or may other- 

 wise be of general interest to persons pursuing mathematical 

 studies, are made the subject of free oral discussion. VI. 

 Scientific Association : — The Scientific Association of the Johns 

 Hopkins University meets once a month for the discussion of 

 subjects of general scientific interest. At these meetings an 

 opportunity is afforded for communicating abstracts of recent 

 mathematical progress, as well as the results of individual 

 research. VII. Mathematical Journal : — "The American Journal 

 of Mathematics " is published quarterly in the City of Balti- 

 more, under the auspices of the Johns Hopkins University, and 

 affords an efficient medium of intercourse between members of 

 the university engaged in original investigation, and a wide 

 circle of mathematicians in America and in Europe. VIII. 

 All the mathematical journals published at home and abroad 

 are taken in by the university. At the Peabody Library com- 

 plete sets of " Crelle's Journal " and the most important scien- 

 tific transactions are also accessible. The university library and 

 reading rooms are open daily from 9 a.m. to 10 p.m. 



The Calendar of the Yorkshire College for its fifth session, 

 1878-9, forms a Tolume of 140 pages. The college has now day 

 classes in the fallowing subjects : — Mathematics, experimental 



