1184 SURFACE AND SURGICAL ANATOMY. 
In the middle line of the neck posteriorly is the nuchal furrow, at the bottom 
of which are the cervical spines and the ligamentum nuche. At the upper part of 
the furrow, about 2 in. below the external occipital protuberance, is the large 
spine of the axis, which can be distinctly felt; a line drawn from it outwards ad 
slightly upwards to the transverse process of the atlas corresponds to the position of 
the inferior ob Nique muscle and, therefore, to the lower margin of the sub-occipital 
triangle. ‘The course of the deep part of the great, Greipel nerve may be mapped 
out by drawing a line from the centre of the above-mentioned line to a point one 
inch external to the external occipital protuberance. At the floor of the sub- 
occipital triangle is the posterior arch of the atlas upon which the vertebral artery 
hes. 
THE THORAX. 
For the convenience of topographical description, clinicians, by the use of 
vertical and transverse lines, have arbitrarily divided the surface of the chest into 
certain definite regions or areas. The vertical lines are: the mzd-sternal, the 
lateral sternal, the para-sternal, the mammary or mid-clavicular, the anterior, mid, 
and posterior axillary, and the scapular. The position of the mid and lateral 
sternal lines is sufficiently imdicated by their names. 
The mammary, hetter termed the mid-clavicular, is drawn vertically down from 
the centre of the clavicles, or, what comes to practically the same thing, from a pomt 
midway between the centre of the supra-clavicular notch and the tip of the acromion 
process. In the male this line usually lies } to ? in. internal to the centre of the 
nipple, which is usually placed over the fourth ne or fifth rib, four inches 
from the middle line. In the child the nipple may be as high as the lower border 
of the third rib. In the female the position of the nipple is so variable that it is 
of no topographical value. In a well-proportioned subject, the mid-clavicular line, 
if prolonged downwards, will be found to be continuous with the vertical Poupart 
line, which crosses the costal margin at the tip of the ninth costal cartilage. 
The para-sternal line, drawn midway between the lateral sternal and mid- 
clavicular, crosses the costal margin opposite the tip of the eighth costal cartilage. 
The anterior, the mid, and the posterior axillary lines are respectively drawn 
downwards from the anterior fold, the apex, and the posterior fold of the axilla. 
The scapular line is drawn perpendicularly through the inferior angle of the 
scapula. 
Of the two transverse lines, the upper, which separates the infra-clavicular and 
supra-sternal regions from the mammary and infra-sternal regions, is drawn at the 
level of the third chondro-sternal articulation ; the lower, which separates the 
mammary and infra-mammary regions, is drawn A the level of the sixth chondro- 
sternal articulation. 
The lateral area of the chest is divided into an upper, or axillary, and a lower, o1 
infra-axillary region, by a horizontal le drawn at the level of the sixth rib. 
In muscular subjects there is a well-marked mesial furrow, the sternal furrow, 
between the sternal origins of the pectoralis major muscles. The inner part of the 
lower border of these muscles forms a curved prominence which, overlying the 
fifth rib, corresponds to the junction of the mammary and infra-mammary regions. 
Below this prominence is the infra-mamimary region, which forms a somewhat flat 
surface corresponding to the upper part of the rectus muscle. In the axillary and 
infra-axillary regions are the prominences caused by the digitations of origin of the 
serratus magnus, the first to appear below the pectoralis major being that which 
springs from the fifth rib. 
The upper border of the sternum lies in the same horizontal plane as the lower 
border of the body of the second dorsal vertebra, the distance between the two being 
about 2 m. The junction of the manubrium and the body of the sternum 
forms a slight prominence or angle, known as the angulus Ludoviet, which, 
although not usually visible, may always be felt. The angulus lies in the same 
plane as the body of the fifth dorsal vertebra. 
The xiphi-sternal junction corresponds to the disc between the ninth and tenth 
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