46 
PHYSIOLOGY OF THE HUMAN BODY. 
column there are 33 vertebre. At the top are 7 cervical} vertebree, or 
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vertebrae of the neck. The topmost, or first cer- 
vical, is termed atlas, because by it the head is 
properly borne up, as the earth was by the 
fabled god Atlas. The second cervical is called 
the aais, because it is the proper axis or joint of 
the neck, the joint between it and the atlas, 
which is a pivot-joint, being that which enables 
the head to turn round. Next to the cervical 
are the 12 dorsal* vertebrae, or vertebrae of the 
back; after which come 5 lumbar? vertebre, or 
vertebrae of the loins. All the above mentioned 
may be separated from each other, and are called 
true vertebre; the rest, namely, the 5 that are 
ossified together, and form the sacrum, or sacred 
bone, and the 4, also united, that form the coccyz,* 
so named from its resemblance to the beak of the 
cuckoo, are called false vertebre. 
It is interesting to know that the skull is © 
merely a prolongation of the backbone, and 
consists of four of the segments or vertebre 
described above. The hollow space which con- 
tains the spinal cord is in these four expanded 
into a capacious chamber (the cranium) for con- 
taining the enlargement of the nerve-substance 
called the brain. The four segments of the spinal 
cord which correspond to the four vertebra, and 
which form the basis of the brain, give off the 
nerves of smell, sight, taste, and hearing. 
The bony part of the trunk is completed by 
THE Ries, which are 24 elastic arches of bone, 
12 on each side, attached behind to the dorsal 
vertebrae, and in front to the sternwm,° or breast- 
bone, by a cartilaginous ligament. It will be | 
seen from fig. 43 that the sternum does not 
extend far enough down to allow of all the ribs 
being directly attached to it; there are, in fact, 
only seven thus attached, which are therefore 
called true ribs. The other five are called false’ 
ribs. Of these, the ends of three are indirectly 
attached to each other and to the sternum by a 
1¥rom Latin cervex, cervicis, the neck. 2 From Latin dorsum, the back. 
8 From Latin lumbus, a loin. 
4 Latin, ‘acuckoo,’ 45 Latin, ‘the breast.’ 
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