. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. THORAX. J023 Along the middle line, this concavity cor- responds with the interval left by the diverg- ence of the two pleura (anterior mediasti- num). In the young subject, transverse lines are seen corresponding to those which occupy the anterior surface ; all of these, except the two between the first and second pieces of the bone, are effaced at a more advanced age. This surface is in relation with many organs contained in the chest, and especially the heart, in front of which the sternum forms a kind of shield. This
. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. THORAX. J023 Along the middle line, this concavity cor- responds with the interval left by the diverg- ence of the two pleura (anterior mediasti- num). In the young subject, transverse lines are seen corresponding to those which occupy the anterior surface ; all of these, except the two between the first and second pieces of the bone, are effaced at a more advanced age. This surface is in relation with many organs contained in the chest, and especially the heart, in front of which the sternum forms a kind of shield. This is exemplified, as al- ready noticed, in the frog, which is provided with a sternum, though it has no ribs. At the lower part of the sternum are many nutritient foramina. Of the borders of the Sternum. — These are thick and marked at each side by seven an- gular depressions for the reception of the cartilages of the first seven ribs, which gives this bone a notched and serrated appear- ance. These angular cavities are separated from each other by semilunar notches, which are longer above than below, where the facettes closely approach each other. The uppermost of these seven cavities is shallow, triangular, and at an early age becomes ingrained with the cartilage of the first rib ; those which follow are deeper, angular, and situated at the ex- tremities of each of the transverse lines. When examined in the dried specimen, they appear more angular and deeper in proportion to the youth of the subject. Of the clavicular extremity.—This is slightly convex, and is the broadest and thickest part of the whole bone. It is slightly excavated from side to side, and presents at each corner a depression for the reception of the sternal end of the clavicle, which bears the name fourchcttc; this is surrounded with irregula- rities for the insertion of ligaments. It fre- quently happens that the two clavicular arti- culations are not at the same height; a fact which was noticed by Morg
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