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MY BREATHING SYSTEM

in breathing can be verified by visual and orthodiagraphic examination. . . . Throughout inspiration there is a back-ward spinał movement which is of importancc in securing maxivnum aeration of the lungs.” This fact, hitherto quite ignored, is fully cxplained by Dr. Halls ])ally in “ An Inąuiry into the Physiological Mechanism of Respiration, with espccial reference to the Movements of the Yertebral Column and Diaphragm.”    (fourn, Anat. and Physiol. Vol. XI.UL,

1908, p. 93 ; 11. also Proc. Roy. Soc., Feb. B., Vol. LXXX., 190S.)

The thoracic cavity is again diminished, and exhalation thus performed, when the chest contracts all over, and the diaphragm ascends (see the dotted lines of Figs. 6 and 8). The lowering of the shoulders and collar-bones is caused simply by tlieir own weight, whilst the downward and inward movement of the ribs, sternum and spine, in ordinary breathing, is caused partly by the weight of the bones and partly by the elasticity of the whole thorax, when the inspiration muscles relax. But when deep-brcathing is concerned, the ribs should, by definite muscular forcc, be pressed further downwards and inwards. The result will be a triple profit: Firstly, a much larger amount of the vi-tiated supplemental air will be driven out of the lungs by each exhalation ; secondly, the smali vesicles of the lungs will get an opportunity of contracting to a fair degrec. thereby retaining tlieir elasticity, and, thirdly, the ribs will not grow rigid, but the thorax will retain or still further inerease its mobility.

Which of these Six Different Expansions are the most effectual in promoting Free Access of Air to the Lungs ?

Opinions upon this point vary greatly. Sonie authors, like Dr. H. H. Hulbert, maintain that the horizontal, lateral

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