OSTEOLOGY AND SYNDESMOLOGY. 27 
which, having attached to it the clavicle and the first and half of the second 
rib, is known as the manubrium. The middle piece, or gladiolus, presents 
six notches on each side: The inferior extremity is known as the «xiphoid 
process: this is thin and cartilaginous, expanded towards the extremity, 
where it is rounded, pointed, or bifid. There is frequently a perforation 
in the centre. 
The ribs, coste (pl. 122, figs. 8, 4, and 5), are twelve in number on each 
side. ‘They extend in an arched manner from the vertebre towards the 
sternum, to which the seven superior pairs are attached by separate carti- 
lages. ‘These are the érue or vertebro-sternal ribs. The five inferior pairs 
do not reach the sternum, but are connected anteriorly with each other and 
to the cartilages of the last true rib; they are known as /alse or ver'tebro-costal 
or asternal ribs. The two last pairs are sometimes called floating or vertebral 
ribs. The length of the ribs gradually increases from the first to the eighth 
pairs, then diminishes again to the last. ‘he external surface of the body 
is smooth and convex; the internal is concave. The upper border is round 
and smooth, and gives attachment to the intercostal muscles. The inferior 
border is thin and marked with a groove on the inner side; its edges give 
attachment to the intercostal muscles, while in the groove are lodged the 
intercostal vessels. 
The posterior end of a rib presents a head, neck, and tuberosity. The 
head is round and divided by a ridge into two articular surfaces, the inferior 
of which is the larger; these are received into the depressions in the dorsal 
vertebre: an interarticular ligament is attached to the middle ridge. The 
head is supported by the neck, which lies in front of the transverse process, 
to which its posterior surface is connected by a hgament. Beyond or exter- 
nal to the neck is the tubercle, which looks backwards and downwards, and 
is divided into two portions. Of these, the internal is smooth for articulation 
with the transverse process of the inferior of the two vertebre, to whose 
bodies the head of the rib is connected. The external is rough for the 
insertion of a hgament. 
The cartilages which connect the ribs with the sternum must be con- 
sidered as part of the skeleton. They are twelve in number on each side, 
and of nearly the same form as the shafts of the ribs. They serve to give 
great strength and elasticity to the thorax, and permit the free play required 
by the lungs and heart. 
B. Articulations and Ligaments of the Thorax. 
The head of each rib is secured to the vertebree by an anterior or stellate 
ligament, an interarticular, and two synovial membranes. The tubercle is 
secured in its socket by a synovial membrane, and by an external posterior 
and an anterior or internal costo-transverse ligament. 
The capsular, stellate, or anterior ligament (pl. 125, fig. 1°) arises from the 
front of the head of the rib, and thence extends over the two synovial 
membranes in a radiated manner, and is inserted by three bands, one into 
the sides of the vertebree above and below, and the third into the inter- 
vertebral substance. The tnterarticular ligament (jig. 1°) arises from the 
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