An inquiry into the physiological mechanism of respiration : with especial reference to the movements of the vertebral column and diaphragm / by J.F. Halls Dally.

  • Dally, John Frederick Halls, 1877-1944.
Date:
[1909]
Catalogue details

Licence: In copyright

Credit: An inquiry into the physiological mechanism of respiration : with especial reference to the movements of the vertebral column and diaphragm / by J.F. Halls Dally. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

    15/26 (page 103)
    Mnrpholofiiccd Note. On account of “ meristic variation ” (Bateson), the spinal segments are not comparable in nuniher among the Vertebratae, the early vertebrate body being lengthened in order that mobility should be increased. The spinal column of the fa^tus and of the young child in type approximates to the simple form found amongst the anthropoid Cercopithecidae, and exhibits onljr rudiments of the compensatory curves later to be developed as a result of the assumption of the erect posture (fig. 4, A). III. Anatomical Dissimilarity of the Two Halves of THE Diaphragm. Anatomically the two halves of the diaphragm differ in size and shape. Idle right half is the larger, and the corresponding portion of the central tendon is bigger than the middle or left portion.s. The right vault stands at a higher level than the left, which latter is depressed and flattened by the superincumbent weight of the heart. One-third of the plateau on which the heart rests is situate to the right of the middle line, and two- thirds to the left. The arch on the left side rises from the central tendon more abruptly than on the right side, and to a much less extent. Its descent also is more sudden, so that the curve is flatter, and may be repre- .sented by an arc of a circle, the centre of which is situate on the seventh left costal cartilage, and whose chord-base is directed obliquely downwards, the lower extremity being further from the median line than the upper extremity, ending above at the lowest point of the fifth costal cartilage and below at the lower border of the eighth rib, a little external to the costo- chondral junction. If the chord-base be bisected, and a perpendicular be let fall upon it, this perpendicular will cut the mid-point of the arc, and, if further produced, will touch the region of the left axilla. In expiration the anterior part of the right side of the diaplu’agm is placed at the highest level; on the left side the mid-portion of the curve takes the highest posi- tion. The rounded contour is maintained by the negative intra-thoracic suction and the positive intra-abdominal pressure, both of which act, the former to the greater extent, in producing a constant tendency to ascent of the diaphragm within the cavity of the thorax. The right crus is far stronger than the left, and has more extensive attachments above than below. It is more median in position than the left crus, and the fibrous band stretched os^er the aorta, directly continuous with the tendon of origin of the right crus, serves as a basis of support for the main part of the median strong muscular fibres which encircle the ot'sophagus and pull down-