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however, as we began to plan a series of observations relating to the question of balance, it became evident that the field was so large that we could hope to cover for the present only some one small phase of the subject, and after a survey of the whole field of inquiry opened by our physiologic research we decided to limit ourselve for this first paper to a study of the very suggestive ques­tion of why such backache was in our clinical experience frequently improved or relieved by the use of corsets or high-heeled shoes.

No one realizes more fully than ourselves how very small a portion of the whole field we have here covered, and our present contribution is regarded by us rather as a report of progress, possibly of therapeutic value, than as a final settlement of even the management of static backache. It is our intention to pursue the lines of

Fig. 4.--Posltlon Induced by bad corset in dotted outline; normal in solid line. In this Instance the shoulders are thrown buck or the normal a little. but not so much as tlle hips. On this and all following records, the solId Yl'l't1cal Indicates the original position of the centre of gravity, the dotted vertical the Induced position.

Fig. 5.-Position induced by bad corset in dotted outline; normal in solid line. In this instance the shoulders the thrown forward of the normal nod the back of the corset.

Fig, 7.-Position induced by good corset in dotted outline. Nor­mal In solid line. The apparent flattening of the lumbar curve in the dotted line Is due tQ the bulging of the soft tissues throu1{h the open space at the back of the corset.

investigation already undertaken further as opportunity may permit.4

PRELIMINARY COSSIDERATION OF PHYSICS RELATIXG TO BALANCE

For the proper comprehension of the practical appli­cation of our experimental work to clinical conditions,

it is necessary at this place to introduce certain elemen­tary points in mechanics which are familiar to every one, for the preliminary problem under consideration reoIves itself into an analysis of the mechanism of the standing position.

These points are the following:

1. The base of support of the upright human figure consists of a trapezoid formed by the outer borders of the feet and lines connecting the back of the heels and the front of the toes.

2. The center of support lies perpendicularly under the center of gravity and must always lie within this trapezoid.

3. For the purpose of studying the mechanism1 by which any weight is borne by a solid body in unstable equilibrium, the entire weight may be regarded as con-

Fig. 9,-Record of the normal position and that Induced by high-heeled shoes, the normal In solid line, the induced position in dotted line.

Fig, l0.-Record of normal position in solid line, corset position in dotted line and position of shoes and corsets in black line broken at longer intervals,

Fig, 11.-Record of Patient 4. whose backache was relieved by corset and Cook bark splint. Original position in solld line; position of relief in dotted line.

centrated in the center of gravity, and the determination of the relation between the center of gravty and the bearing points determines the lines of stress.

Our observations show that in the erect position the center of gravity of the body lies in front of the ankle-­joints, which are held from dorsal flexion in this posi­tion by the gastrocnomius muscles. The center of gravity also in front of the knees, which are similarly held in position by the hamstring and quadriceps exten­sor muscles. The center of gravity lies also anterior to the sacra-iliac joints and most of the vertebral joints. The position of the acetabula cannot be determined in the erect position in the living individual because we have no means of locating them from any available landmark. If we were able to determine the position of the acetabula in the antero-posterior plane it would be po­sible to state definitely, frol11 the relation of the center of gravity to them, whether the trunk in the erect posi­tion would tend to fall forward or backward at their level. But from the impossibility of obtaining definite