Clinical tuberculosis . s with its attachments to the lumbar vertebrae. Contractionof this portion of the diaphragm exerts a very marked force onthe al)dominal contents. When the diaphragm contracts the intra-alxldiiiinal pressure is increased and tlie abdominal muscles are INSPIRATORY ACT AND CIRCULATION 301 pushed outward carrying the lower central arch with them, andat the same time other muscles of inspiration contract and raisethe ribs. The result of this action is shown in Fig. 47. The effect of lessening the diaphragmatic action is shown inPig. 60, A and B, page 328. In A we see that as
Clinical tuberculosis . s with its attachments to the lumbar vertebrae. Contractionof this portion of the diaphragm exerts a very marked force onthe al)dominal contents. When the diaphragm contracts the intra-alxldiiiinal pressure is increased and tlie abdominal muscles are INSPIRATORY ACT AND CIRCULATION 301 pushed outward carrying the lower central arch with them, andat the same time other muscles of inspiration contract and raisethe ribs. The result of this action is shown in Fig. 47. The effect of lessening the diaphragmatic action is shown inPig. 60, A and B, page 328. In A we see that as the diaphragmcontracts the lower ribs are forced outward and the intrathoracicspace is enlarged. In B we have the motion of the left half ofthe diaphragm lessened with a resultant decrease in the normalinspiratory enlargement of the left side of the chest. This con-dition is frequently met with in pulmonarj- tuberculosis bothas a result of reflex action through the phrenies and as a resultof inflammation of the Pig. 47.—Illustrating the movement of the ribs and sternum during inspiration. Inspiratory Act and Circulation.—One of the most importantfactors in the circulation of the blood, outside of the hearts ac-tion itself and the elasticity of the vessel walls, is the suction ex-erted upon the blood column by the thoracic cavity duringrespiration. The part of the diaphragm in this act can be ap-preciated from the following from Wenckebach :» The diaphragm »Uber nathologische Beziehungen zwischen Atmung und Krieislauf beim klinischer Vortrage (Volkmann) Innere Medizin, No. 140 and 1-11, 1907. Sammlung 302 COMPENSATORY CHANGES IN TUBERCULOSIS of mammals is the most important factor in the filling of theheart, while in amphibians and the lower vertebrates it is theonly factor. The pressure Avithin the thoracic cavity outside of the air pas-sages is negative and decreased with every inspiration. The di-aphragm contracts forcing the abdominal viscera
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