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MY BREATHTNG SYSTEM

diaphragm, which, having by this timc desccnded until its central tendon exerts firm continuous pressnre upon the intra-abdominal viscera, now executes the second part of its dual action in contracting its ring of costal fibres. These, being attached at an obliąue anglc to the ribs, in contr action raise the ribs upwards and outwards, being aided by the external intercostals and intcrcartilaginous portions of the internal intercostals.”

As we may see, Dr. Halls Daily has not quite cmancipated himself from the old theory of the diaphragm as a rib-moving power. The explanation is, I tłiink, that the X-ray photo-graphs and orthodiagrams certainly give an exact illustra-tion of facts, but they do not tell us anything about the cause and eftect of what we see.

My Own Theories about the Diaphragm.

\Yhen we breathe very ąuietly -for instance, when rcsting or sleeping—the diaphragm " pulsates ” on its own account, and that quite unconsciously, in a manner similar to the bcating of the heart. In this case the sliglit contractions and relaxations of the diaphragm form, in many persons, almost the only motive power of their breathing. But when morę cliange of air is needed, part or the whole of the thorax expands and contracts, moved by muscles which, in well-developed individuals, are much stronger than the diaphragm. Even if it still continue its own smali “ pulsations,” the diaphragm is now, as a whole, forced to give way to the move-ments of the lower ribs and sternum, to which it is attached. It will be easily understood that, when the ribs are brought nearer to each otlier, the whole middle part of the diaphragm will move upwards; and when the ribs are moved away from each other, this central portion of the diaphragm will sink, even though the ribs are at the same time somewhat raiscd. It is only the outer annular border or margin of the

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