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A Contribution to the Study of the Mechanism of Respiration, 
with Especial Reference to the Action of the Vertebral 
Column and Diaphragm. 
By J. F. Hatts Datty, M.A., M.D. Cantab. 
(Communicated by Professor Sir T. Clifford Allbutt, K.C.B., F.R.S. 
Received January 24,—Read February 6, 1908.) 
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, to 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 he 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. 
SUMMARY OF THE RESULTS OF THE INVESTIGATION. 
I. Results obtained by Orthodiagraphic Measurement of Changes in the Trunk 
which occur during Respiration. 
One hundred healthy subjects, of ages varying between 15 and 35, were 
examined, the average measurements being recorded as follows :— 
(1) The neck is shortened 10 mm., and widened, on the right side 9 mm., 
on the left side 7 mm. 
(2) The shoulders are raised on the right side to a greater extent than 
on the left, the average on the right being 16 mm., that on the left 
14 mm. 
(3) The presternum moves 30 mm. in an upward, and 14 mm. in a forward, 
diameter. ) 
(4) The clavicles execute a combined upward, forward, and outward 
* ‘Brit. Med. Journ.,’ September 14, 1907, p. 651. 
