The relation between the movements of the eyes and the movements of the head: : being the fourth Robert Boyle Lecture delivered before the Oxford University Junior Scientific Club on Monday, May 13, 1895, / by Alexander Crum Brown.

Date:
1895
Catalogue details

Licence: Public Domain Mark

Credit: The relation between the movements of the eyes and the movements of the head: : being the fourth Robert Boyle Lecture delivered before the Oxford University Junior Scientific Club on Monday, May 13, 1895, / by Alexander Crum Brown. Source: Wellcome Collection.

Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.

    18/28 (page 18)
    3. The superior and posterior canals of the same side make approximately equal angles with the mesial plane. In all cases which I have examined, the angle between the posterior canal and the mesial plane is somewhat larger than that between the superior canal and the mesial plane. From the bilateral symmetry, therefore, the superior canal of the one side is nearly, but not quite, parallel to the posterior canal of the other side. In the discussion of the way in which the system of canals may be supposed to act, I shall for convenience assume that these canals are parallel, as the deviation from exact parallelism only complicates but does not at all vitiate the argument. 4. In man, and in a large number of other animals, the three canals are very nearly at right angles to one another. But in a good many of the animals I have looked at, the superior and posterior canals make with one another an angle considerably greater than a right angle. Looking at the six canals as forming one system we see that we have three axes (in man and some other animals rectangular axes, in some other animals with two of the axes inclined), and that at right angles to each axis there are two canals, one in the one internal ear, the other in the other; these two canals having their ampullae at opposite ends, so that if rotation take place about the axis the ampulla in the one case precedes the canal, in the other follows it. The vertical axis, as we may call that at right angles to the two external (or horizontal) canals, is pretty nearly vertical in most animals, in the usual position of the head when the animal looks to the horizon; in man it is not exactly so,