Our Breathing Mechanism.

Auckland Star, Volume XVII, Issue 199, 25 August 1886, Page 4

Our Breathing Mechanism.

" Breathixg in," if we reflect upon the nature of tho act in our individual person?, ia a matter of some trouble, It ijvolvcs a largo amount of labour : it gives us much muscular trouble, so to epoak. In the case of a deep inspiration we exaggerate tho effort 8 c i in normal breathing, and we may therefore appreciate still more exactly tho expenditure of energy required to carry on thia necossary functijn ot vitality. ]!ut " breathing out" is a widely different matter. We let the chest "go,'as it wore, at tho close of inspiration, aud, without an effort, t returns to its position of re3t. Wo expend force in " breaihingin ;" wo appear to exert none in ''breathing out " The former U a muscular act performed by a complex eerias O:. mueclte, and participated in by the lungs and other structures connected with the chest. Tho latter is an act which partakes, even to tho common understanding oE the nature of a recoil: and in this latter supposition we perceive how economy of labour in the human domain ia subserved Breathing, then, means that wee nlarge the chest by thq action of certain muscles, that tho pressure of air in the lungs becomes reduced as compared with that outaide, and that in consequence air rushes into the lungs through tbe windpipe until an equality of air-pressure inside and outside tho lungs is produced. This is tho act which ie accomplished forcibly, against gravity, and by aid of very considerable muscular power. Wo are faid to perform no less than twenty one foot tons of work by means of our respiratory muscles in twentyfour hours —that ia to say, the work of these muscle?, extending over twenty-four hours' period, if gathered into ono huge lift, would rise twenty-one tons weight one foot high. By a little additional muscular labour wo tako in a deop breath, still further enlarge the chest, and inhale an additional quantity of air. Tho groat muscle named the diaphragm or " midriff," which forms the floor of the chest, is the chief agent involved in the act of inspiration. It descends, whilo the ribs aie elevated, and as the chest enlarges, tha inflow of air takes place. The lungs themselves aro highly elaatie bodies. They follow tho movements of the chest walls, and thus expand and contract — they euffar dilatation and compression as the chest wall 3 move in the acts of respiration. But, whon ordinary "breathing out'" is studied, we see that it is aa clearly a mattor of recoil as has been statod, as "breathing in ■' is a matter of exertion. Hore elastic reaction etep3 in to complete the full act of broathing. Naturo saves her onorgiea and huebands herstrength in thia truly physiological division of labour. When wo inspire, the lung-substance, elastic in itself, is put on the stretch ; the cartilages of ribs and breast-bono are similarly elevated and expanded, and tho whole chest is, so to speak, forced into its position of unreßt. Then comas the reaction. The muscles of inspiration cease their action ; they relax, and the elastic lungs recover ihemsolveß and continuo to aid in forcieg out tho a;r they contain. So, also, when tho ribmuscles have come to the end of their tether in elevating those bonea, the elastic recoil of the ribs and breast-bone serves to diminish tho capacity of the chest, and to further expel the air from within its contained lungs. Laboured or excessive breathing, as most readers know, calls into play extra help from muscles not ordinarily used in natural respiration. This fact takes us out of the normal way of life into the consideration of abnormal or diseased Btates, and demonstrates that the economy of Nature disappears when phases of morbid action fail to bo subserved. In natural breathing,however, we eee'eonservation once more in tho easy recoil which follows the muscular labour of inspiration. Tho phsiology of a Bigh aDd its rolief can bo readily appro ciated on the_ basis which shows how the easy act of expiration ia correlated with the moro laboured action and duty of enlarcin" tho chest,—" Dr. A. Longman's Magazine for June." A New York editor says that Gonoral Wolseley ought to bo "sat upon as a dangerous firebrand." Who wants to sit 1 upon a firerand ?