On the Study of the Mechamsm of Resprraton, etc. 188 
movement, the vertical range of their inner ends on the right side being 
28 mm., on the left side 27 mm.; of their outer ends, on the right side 
21 mm., on the left side 16 mm. The divergence from the median line is, 
on the right side 7 mm., on the left side 6 mm. 
(5) The meso-metasternal articulation either may remain in the same 
horizontal plane, or may rise as much as 46 mm. The average ascent is 
28 mm. 
(6) Widening of the infra-costal angle occurs, the interval between the 
costal margins, measured on each side at a level of 30 mm. below the meso- 
metasternal articulation, being increased by 26 mm. 
(7) The trunk is widened at the level of the meso-metasternal plane 
9 mm. on the right side, and 8 mm. on the left, and midway hetween the 
meso-metasternal plane and lowest point of the costal margin 9 mm. on the 
right side, and 11 mm. on the left. 
(8) The umbilicus is retracted and drawn upwards in deep respiration for 
a distance of 13 mm., on account of the active recession of the abdominal 
wall produced by the contraction of the abdominal muscles, which, in this 
phase of respiration, act as antagonists of the spinal muscles. The upward 
displacement of the umbilicus is usually to the right, but may be median 
or to the left, the lateral deviation being 7 mm. 
(9) The heart and pericardium together undergo important changes in 
size and position as a result of the respiratory movements, being lengthened 
and narrowed in inspiration, shortened and widened during expiration. 
(10) The pericardium, at the level of its attachment to the central tendon 
in the adult, measures 80 mm. in antero-posterior diameter. 
II. The Movement of the Vertebral Column in Respiration. 
I can find no reference to this movement in eight of the latest and best 
known text-books of physiology. That this movement is actual and of 
mechanical advantage in breathing can be verified by visual and ortho- 
diagraphic examination. In the latter the subject is rotated through an angle 
of 30° to 45° into the “lateral oblique” position. The shadow of the 
vertebral column is seen clearly separated from that of the pericardium and 
great vessels by a transradiant triangle, the base of which is formed by the 
upper surface of the diaphragm. On inspiration the posterior wall of this 
triangle, formed by the vertebral column, recedes, to a greater extent below 
than above, and so opens out the interval from before backwards. With 
subsequent expiration the spine advances. 
Hiplanation of the Spinal Respiratory Movement.—A general rectification of 
the curve of the thoracic spine takes place. In eight orthodiagraphic 
