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pleurapophysis, or ' vertebral rib' of comparative anatomists, ' pars ossea costee' of 

 anthropotomy, presents a small flat subcircular surface, c", for articulation with that 

 on the base of the neurapophysis forming the upper angle of the body of the vertebra 

 in advance of the segment to which the rib belongs. The neck of the rib rapidly 

 expands as it quits the head, developes the convex oval surface, n", on its upper part 

 for the concavity on the neurapophysis of its own vertebra ; and is indented behind 

 where it joins the tubercle. The oval convex articular surface, d", for that on the 

 diapophysis, is situated on the upper and towards the back part of the tubercle. The 

 body of the rib is moderately convex on its outer side, more convex transversely on 

 its inner side, where the convexity is bounded by a groove on each side, extending 

 half-way down the rib, near its rather sharp margins: in its lower half the rib be- 

 comes a little broader and less thick. The outer surface of the rib is well marked 

 by grooves and ridges for muscular attachment ; the best-developed eminence being 

 at a short distance from the tubercle ; and the largest and deepest groove being 

 behind the tubercle. 



The hsemapophysis, or 'sternal rib,' h, is a straight subcompressed bone, with a 

 very irregular surface, which is somewhat convex on the inner side, but is traversed 

 by strong oblique ridges with intervening deep and wide channels on part of the outer 

 side. The surface of junction with the pleurapophysis is a very rough and irregular 

 one for ligamentous union : the opposite end of the hsemapophysis divides into two 

 convex condyles, s 1 s 1 , separated by an oblique, deep and rather narrow groove; the 

 outer condyle projects further than the other; on the shorter one the articular sur- 

 face passes continuously from one side to the other, describing a semicircle; on the 

 longer condyle the articulation is divided by a median constriction into two oval con- 

 vex surfaces. One half of each of the condyles articulates with a corresponding con- 

 cavity on the 'sternal bone' (hs) of its own segment, the other half of each condyle 

 with the contiguous sternal bone. 



The sterneber or sternal bone, completing, as ' hsemal spine,' hs, the typical seg- 

 ment in question, is a cuboid piece, divided into an outer or peripheral, and an inner 

 or central portion. The outer portion is subpentagonal, having its four corners exca- 

 vated by as many concavities for the hsemapophysis ; the two upper concavities, s" s", 

 being divided by a flat rough tract, the two lower concavities by a rough tuberosity. 

 The outer surface is flat and rough. The inner portion, or that next the cavity of 

 the chest, is larger than the other and has a hexagonal contour ; the four angular 

 concave articular surfaces, s", *", for the hsemapophyses being separated, at the sides 

 of the bone, by rough tracts ; and, above and below, by a flat articular surface, hs, by 

 which the bone articulates with contiguous sternal bones. The inner surface of this 

 portion is flat and rough, having been apparently covered by a strong aponeurosis in 

 the living animal. Thus the whole bone presents not fewer than ten articular sur- 

 faces, viz. a flat semicircular one above or in front of, and a similar one behind, the 

 posterior division ; and two concave articulations, s",s', on each side of both divisions 

 for the double condyles of two pairs of haemapophyses. 



