A contribution to the study of the mechanism of respiration, with especial reference to the action of the vertebral column and diaphragm

In studying the alterations which occur in the shape, size, and position of the internal organs as the result of their functional activity, previous observers have worked at a disadvantage. During the past nine years X-rays methods, though indicating an advance in our knowledge of abdominal and thoracic visceral movements, have not been of absolute utility, since the rays, being divergent, produce magnification of the shadow of the object. Hence, exact measurements have been unattainable. In the present investigation the chief results have been obtained by means of Groedel’s orthodiagraph, which Dr. Hugh Walsham and myself have been the first, to our knowledge, two work with in this country, and of which we have already published a detailed description. By means of this instrument it is possible, with almost mathematical accuracy, to measure motionless objects which lie in a plane parallel with the vertical transverse plane of the body, and to measure moving objects with greater approach to exactitude than can be obtained in any other manner.