-1908.] Study of the Mechanism of Respiration, ete. 185 
movement is but little dissimilar, the difference, if any, being usually in favour 
of the right half. 
IV. The Means by which the Diaphragm is supported. 
In another paper I have dealt with the superior, or thoracic, and the 
inferior, or abdominal, supports of the diaphragm. | 
V. Level of the Diaphragm. 
(1) After Death—tThe cadaveric position of the diaphragm indicates only 
the position of expiration. From the results of an examination of 80 
dissecting-room and post-mortem-room cases, I find that the average highest 
point of the dome of the diaphragm is situate, on the right side at the level of 
the upper border of the 5th rib in the mid-clavicular line; on the left side, 
in the mid-clavicular line at the lower border of the 5th rib. This 
corresponds with the results of orthodiagraphic measurement in bodies of 
healthy persons who have met with sudden death. 
(2) During Life-—Owing to the great variability in position of the land- 
marks usually adopted in measuring the range of the diaphragm, I have 
taken the meso-metasternal articulation, 2.¢., junction between gladiolus and 
ensiform, as the basis from which to measure, and a line drawn horizontally 
through this point—the meso-metasternal plane—as the plane to which the 
level of the rise and fall of the diaphragm may be referred, and all ortho- 
diagraphic measurements of the position of the domes and central tendon 
have been taken in millimetres above and below this plane. 
VI. Absolute Range of Movement of the Diaphragm. 
The absolute range of movement of the diaphragm between deep inspira- 
tion and expiration in the adult male is, on the right side 34 mm., on the left 
side 32mm. The range in adult females amounts to 27 mm. on the right 
side, and 25 mm. on the left side, making the total average range 30 mm. on 
the right side, and 28 mm. on the left. 
The fact that these figures are only about half as great as those previously 
‘given* is due to the greater accuracy of orthodiagraphic measurement. In 
quiet respiration the total average movement is 12°5 mm. on the right side, and 
12 mm. on the left. Hence this movement is approximately equal on the 
two sides, whilst in deep breathing, the excursion is, for most people, slightly 
greater on the right side.than on the left. In diagnosis, the movement in 
deep respiration is the important one to observe. 
* The ‘ Lancet,’ June 27, 1903, p. 1802. 
