On the mechanism of respiration / by Francis Sibson, Esq.

  • Francis Sibson
Date:
1846
Catalogue details

Licence: Public Domain Mark

Credit: On the mechanism of respiration / by Francis Sibson, Esq. Source: Wellcome Collection.

    19/70 page 15
    into the chest, and F3 and F4 are front views of the rib of a Pig1. E2 shows the for- ward and backward thrust on inspiration, or increased distance between the sternum S and vertebrae V, and F24, show the lateral thrust. The sternum S and vertebrae V not admitting of further separation, the raised costal cartilage acts like a crank on the end of the rib jointed to it, and pushes it outwards. The area of the chest be- tween the opposite ribs is thus increased, and the elevation of the rib and cartilage is extended in two directions, one direction (E2) to increase the depth, the other (F2) the width of the chest. 38. In the Pig, as we have seen, the elevation of the rib and cartilage is distributed in two directions, one direction forwards and backwards, the other outwards. The outward, or lateral thrust, is by far the greatest. There is in the Calf considerable forward movement of the sternum in addition to the lateral expansion. The lower costal cartilages are longer than the upper, consequently the lower part of the sternum is thrust further forward than the upper, exactly as it is in birds, and for the same reason (§ 22). In the Sheep, when the lungs are distended, the vertebrae are, I believe, pushed slightly backwards, but nearly the whole of the force is expended in the lateral thrust; the chest, though but slightly deepened, is much widened. 39. Inspiratory changes in the position of the curves and surfaces of the ribs. The space between the ribs is further increased by the change in profile of the curves of the ribs. In expiration the upper edge (diagram E1) and the inner surface of the rib (diagram F1) are each slightly curved. In inspiration (diagram E1), when the rib is raised, the curve of the inner surface is very greatly increased at the ex- pense of that of the upper edge, the curve of which entirely disappears, giving place to a straight line; the form of the rib remains the same, but its profile and the direc- tion of its surfaces are changed. 40. Lateral expansion of the chest from the varying profile of the curves of the ribs in the Ass. In the Ass, the unyielding cartilage is firmly fixed to the rib so as to form one piece with it. The whole of the lateral thrust is due to the different direction of the costal curves. Nearly the whole of the respiratory movements go to increase the width of the chest. The sternal end of each cartilage is a little raised, and the ver- tebral end of the rib is slightly depressed ; the sternum moves forwards and upwards with the cartilages ; the spinal column backwards and downwards with the ribs ; the increase in depth is very slight. ♦ 3x2
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