THE RIBS. 333 
Each rib is divisible into a body and two extremities. The body has 
two flat surfaces and two borders; the latter of which are concave and 
thin, anteriorly convex, and rounded posteriorly. The head or superior 
extremity varies in the true and false ribs, as will be better seen by 
reference to the engraving (Fig. 21), where one of each kind is delineated. 
The cartilages are all attached to the ribs by firm union of their fibres to 
2 ae 
Fia. 21.—A TruE anpD FALseE Rip. 
A. Profile view ofa left true or sternal rib. 6. Asternal cartilage. 
2. Tubercle for attachment to transverse C. View of the upper extremity of sternal rib 
process of vertebra. inverted to show the mode by which 
3. Head, true. the articulating surfaces on the upper 
4. Body. part of the rib correspond to the nine 
5. Junction of rib and its corresponding anterior dorsal vertebra. 
sternal cartilage. 1. Body. 
6. Sternal cartilage. 2. Tubercle, separate. 
B. Profile view of left false or asternal rib (eigh- 3. 4. Head (true), showing the two surtaces 
teenth). of articulation, and the notch in wnich 
2. Tubercle fused in one with the head. the round ligament is attached. 
3. Head. D. View of the last asternal rib, a'so inverted to 
4. Body. show the fusion of tubercle and head 
6. Junction of false rib and asternal carti- together. 
lage. 2. 3. Tubercle fused with head. 
a deep pit in the extremity of each rib. They serve the double purpose 
of giving elasticity to the thorax in the act of respiration and of enabling 
it to bear severe shocks without fracture. 
Among the several ribs, the first is the thickest and shortest, and is 
irregularly arched ; the second is very slightly curved: from this point 
they increase in length and breadth to the ninth; from the ninth to the 
