A text-book of human physiology : designed for the use of practitioners and students of medicine / by Austin Flint.

  • Flint, Austin, 1836-1915.
Date:
1876
Catalogue details

Licence: Public Domain Mark

Credit: A text-book of human physiology : designed for the use of practitioners and students of medicine / by Austin Flint. Source: Wellcome Collection.

Provider: This material has been provided by The University of Leeds Library. The original may be consulted at The University of Leeds Library.

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    a late elaborate work assumes that the question is still left in considerable uncertainty. The most extended researches on this point are those of Beau and Maissiat (Archives generalen de medecine, 1843), and Sibson {pUlonopMcal Transactiona, 1846). The latter seem to settle the question of the mode of action of the intercostals and explain satis- factorily certain points which even now are not generally appreciated. More recently, Onhiius has shown, by experiments upon a decapitated animal, that the external inter- costals raise, and the internal intercostals depress the ribs, thus confirming the views of Sibson. We shall first note the changes which take place in the direction of the ribs and their relation to each other in inspiration, before considering the way in which these move- ments are produced. In the dorsal region, the spinal column forms an arch with its concavity toward the chest, and the ribs increase in length progressively, from above downward, to the deep- est portion of the arch, where they are longest and then become progressively shorter. According to Sibson, during inspiration the ribs approach to or recede from each other according to the part of the arch with which they articulate; the four superior ribs ap- proach each other anteriorly and recede from each other posteriorly; the fourth and fifth ribs, and the intermediate set (sixth, seventh, and eighth), move further apart to a moderate, the diaphragmatic set (four inferior), to a great extent. The upper edge of each of these ribs glides toward the vertebrsB in relation to the lower edge of the rib above, with the exception of the lowest rib, which is stationary. These movements increase the antero-posterior and transverse diameters of the thorax. As the ribs are elevated and become more nearly horizontal, they must push forward the lower portion of the sternum. Their configuration and mode of articulation with the vertebras are such, that they cannot be elevated without undergoing a considerable rotation, by which the concavity looking directly toward the lungs is increased, and with it the lateral diameter of the chest. All th e intercostal spaces posteriorly are widened iu inspiration. The ribs are elevated by the action of the external inter- costals, the sternal portion of the internal intercostals, and the levatores costarum. The external intercostals are situ- ated between the ribs only, and are wanting in the region of the costal cartilages. As the vertebral extremities of the ribs are the pivots on which these levers move, and as the sternal extremities are movable, the direction of the fibres of the intercostals from above downward and forward renders elevation of the ribs a necessity of their contrac- tion if it can be assumed that the first rib is fixed or at least does not move downward. The scalene muscles ele- vate the first rib in ordinary inspiration; aud, m deep in- sniration this takes place to such an extent as to palpably Yia. 4S.-Elewition qfthe ribs in spuatiuu, luio i Inwpr rib's Theoreti- inspiration. (Beciard.) carry with it the sternum and the lower rms. lueoreui The dark lines represent, the ribs, , p-rtprnal intcrcOStals can do nothmg IlUt sternum, and costal cartilages in cally, then, tlie exierudi inspiration. render the ribs more nearly horizontal. If the external intercostals be exposed in a living animal, the dog for exan.p^ m which the costal type of respiration is very -a^'^ed, c o- convince any one that these muscles enter m o ^^I'^^I^^^^^ directed to the been observed by Sibson and many other physiolog sts. 2 ' sta^ ^^t^^ees, their sternal portion of the internal intercostals, ^^'^^'^^'^'^'^''''''''''^ fibres having a direction from above downward -Jt^}^^^l^':^l l'^''^^^ X, ^eath, they enter into action with inspiration. By artificially -Af^^f f e 'f ^.^^^ Sibson confirmed these observations and ^^^^^^^'^^ ^Xe all separated air the fibres of these muscles are shortened. In inspiration, the ribs arc sep.