Bauhaus-Universität Weimar

The Cyclopaedia of Anatomy and Physiology, vol. 4: Pla [corr.: Ple] - Wri
Todd, Robert Bentley
same characters in both sexes. There is little 
difference in the height of the two apices. The 
elevation of the liver on the right side does 
not necessarily cause the right apex to be 
the higher. The right lung is more shallow 
than the left; but this is not because it is 
“ pushed up,” but because, in order to ac¬ 
commodate the liver, there is less lung- 
substance on the right side. If the mean of a 
series of observations represents the right 
side of the thoracic cavity as equal to 151, the 
left may be given as 182. The same may be 
said of both sexes. 
(b) Posterior region. — If we examine this 
region upon a cast of the thoracic cavity, we 
observe in the middle line a deep fossa, formed 
by the projection, to the very centre of the 
thoracic cavity, of the bodies of the dorsal 
This fossa is wider towards the base of the 
thorax, as may be seen by comparing the dif¬ 
ferent sections of the cast (compare the 
notches, 10, 11, and 12, with those of 3,4, and 
5 in fig. 668.). 
Fig. 668. ; 
Sections of a cast of the thorax showing the space 
encompassed by each pair of ribs respectively. 
The bodies of the thoracic vertebrae, form 
almost a complete septum ; they are certainly 
a central column of support for the whole 
trunk of the body, bearing an equal distri¬ 
bution of the superincumbent weight in all 
directions. There is no part of the skeleton 
which more strikingly demonstrates that man 
was destined for the erect posture, than this 
central position, together with the increasing 
dimensions from above downwards, of the 
vertebral column. These conditions exist only 
in the human subject. The groove in the cast 
formed by the dorsal vertebrae is directed 
upwards and fonuards, so that at the apex of 
the thoracic cavity it completely divides the 
lungs, producing two little cones laterally for 
the lungs, forming the right and left apex. 
At the base of the thorax this perpendicular 
column again completely divides the lower 
lobes of the two lungs. The shape of the 
posterior part of the cast is that of a curve 
directed upwards, and sharply forwards, near 
the apex (j£g.667.). This curve near the apex 
is, like the form of the apices, ,very various. 
An inflated lung assumes the same shape 
as this cast, giving even the marks of the ribs. 
The student, in order to have a correct idea of 
the lungs, should remove them from the body 
with the heart attached ; then inflate them to 
their utmost, when their shape, their lobes, 
and relative mass before and behind, are clearly 
If now we inspect the cavity of the thorax 
itself, we find that the bodies of the vertebrae 
by their projection as above described, divide 
the posterior portion of the chest into 
two vast lateral grooves, which lodge the 
posterior portions of the lungs; these two 
grooves, partaking of the form of the thorax, 
are consequently conical in their configuration. 
They lodge fully one half of the entire lungs. 
This is worthy of remembering in reference to 
diagnosis, particularly when pneumonia is sus¬ 
pected ; in such cases auscultation of the dorsal 
region demands as much attention as that 
of the anterior region. Though less vulnerable 
to phthisis pulmonalis, yet it may lodge disease 
in parts comparatively remote, and where in¬ 
flammation may insidiously gain serious ground 
upon the patient, particularly in children. 
(c) Lateral region. — This precisely corre¬ 
sponds with the external lateral view of the 
thorax (compare fig. 667. with fig. 680.); it 
presents indentation of the ribs, resembling a 
diagonal, curved, grate. 
(d) The base of the thoracic cavity has been 
described above. 
Conformation as affected by age and sex. 
— Age alters the conformation of the chest. 
In the earlier periods of existence the thorax 
is the smallest of the three great cavities, 
probably from the inactivity of the lungs! 
In the fœtal thorax the antero-posterior dia¬ 
meter exceeds the transverse diameter, the 
sternum projecting forwards, and the heart and 
thymus gjand filling up the middle of the cavity. 
The ribs in fœtal life are less curved, and conse¬ 
quently those deep grooves, seen in the interior 
of the chest on each side the spine, formed 
by the angle of the ribs, so conspicuous in 
after life, are almost wanting ; the vertical 
depth also is much less at this period, because 
the lungs are unexpanded and unemployed, 
while the abdominal viscera, particularly the


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