1888 .] Prof. Cmm Brown on Canals of Internal Ear. 149 
Monday, February 6, 1888. 
Sir william THOMSON, President, in the Chair. 
The following Communications were read : — 
1. On a Mode of Exhibiting the Action of the Semi- 
circular Canals of the Internal Bar. By Professor 
Crum Brown. 
The problem is to contrive an apparatus in which, by means of 
inertia, acceleration of angular velocity about any axis in either 
sense may he observed and approximately measured. 
In the internal ear we have such an apparatus, if we consider the 
two ears with their six canals as forming one organ, each canal 
sensitive to acceleration in one sense about the axis at right angles 
to the average plane of the canal. The model shown illustrates the 
principle. It consists of a rectangular frame turning on a vertical 
axis parallel to the short sides of the rectangle. On each side of 
this axis there is a heavy wheel with its axle vertical. Each wheel 
