INDIVIDUALITY OF BREATHING

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Abstract
The incidence and degree of activity of the respiratory muscles during eupnea was studied by a systematic mapping of inspiratory and expiratory action potentials. The results from a series of 27 expts. show great variations in participation of respiratory muscles possibly accounting for the diversity of opinion on the function of these muscles. The interchondral portion of the Mm. inter- costales interni and the M. diaphragma invariably participated in the act of breathing. Participation of the interosseus portion of the Mm. intercostales interni, Mm. intercostales externi, Mm. levatores costarum, M. transcostar, M. triangularis sterni, M. obliquus externus ab-dominis and M. obliquus internus abdominis, M. trans-versus abdominis and M. rectus abdominis varied with the individual animal. The interchondral portion of the Mm. intercostales interni contrary to current opinion was not exclusively an inspiratory muscle. From the 6th, 7th, 8th, or 9th interspaces it contracted, in scattering cases, during the phase of expiration. The interosseus portion of the Mm. intercostales interni varied greatly m activity. Extensive non-activity was common. Expiratory activity occurred mainly in the posterior half of the chest. The Mm. intercostales externi varied in function and activity. Inspiratory contractions were confined mainly to the anterior half and dorsal aspects of the chest. Expiratory activity was confined to the posterior half. Simultaneous inspiratory and expiratory activity in these respective areas was not uncommon. The remaining muscles (M. obliquus externus abdominis, M. obliquus internus abdominis, M. transversus abdominis, M. triangularis sterni and M. transcostar), all expiratory in function, varied in incidence and degree of activity. The M. cutaneous abdominis frequently functioned as an expiratory muscle.[long dash]-Combined analysis of the results on inspiratory and expiratory muscles indicates that every individual possesses its individual respiratory pattern of breathing. Individuality of breathing is a resultant of varying combinations of varying muscle patterns, of varying contraction intensity patterns, and varying muscle sequence patterns. In 2 dogs muscular activity during the expiratory phase of breathing was entirely missing. It must, therefore, be concluded that expiration may be a purely passive phenomenon. In the remaining 25 dogs varying degrees of active expiration were encountered.

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