Page:Popular Science Monthly Volume 59.djvu/407

Rh to avoid taking too wide a range of discussion, we shall treat the subject as though the influence of the plane of vision were in all cases uniform, which is not strictly the case; yet, for our present purpose, we may omit the exceptions, and the statements that follow must be accepted as general and as including the proviso, other things being equal.

Examining then the pose of the head and body in their relations to the position of the visual plane more in detail, it will be found that when the visual plane is quite low not only is there a tendency for the individual to elevate the chin and throw the head back, but the muscles of the whole back, even those of its lower 'part, are put in a state of tension. This tension is so considerable that in a great many instances among persons who are not very strong the resulting habitual pains of the muscles engaged are often mistaken and treated for diseases of internal organs or of the spine year after year.

An element of the facial expression with this direction of the visual plane is the pronounced elevation of the brows upon the forehead and the somewhat drooping appearance of the eyelids (see Fig. 4). There are other facial expressions characteristic of this depressed plane of vision which may be passed over in this connection.

The attitude and gait of the individual are also generally influenced by the downward direction of the visual plane. In walking the shoulders are thrown back and the chest is thrust forward. The foot, in many cases, swings forward considerably beyond the limit of the completed step, so that it is drawn somewhat backward as it comes to the ground.

While persons of this class are more liable than others to certain physical complaints and nervous disturbances which can be traced directly to this ocular condition than are those whose eyes are adjusted for a higher plane, they are, on the other hand, compared with this latter class far less subject to certain other forms of diseases and affections.

A single example will serve to illustrate this proposition. Although the illustration relates to a trouble with the eyes themselves it would be easy to present many examples to illustrate immunity of the same class of persons from a variety of more general affections.

A few years since a distinguished oculist of one of our southern cities announced that trachoma, that form of eye trouble commonly known as granular lids, and which is one of the prolific sources of blindness, is unknown among pure negroes. The discussion of this proposition, after occupying the attention of oculists for some time, was at length taken up in a different way by a distinguished colleague in Constantinople.

This gentleman wrote to oculists in all parts of the world asking