16 COMPOSITION OF BONES. 



the armadillo, are instances of its accumulation upon or 

 near the surface of the body; and hence the ball-proof 

 character of the skin of the largest of these mailed exam- 

 ples. The most constant position of bone is around the 

 central masses of the nervous and vascular systems, with 

 rays thence extending into the middle of the chief mus- 

 cular masses, forming the bases of the limbs. Portions 

 of bone are also developed to protect and otherwise sub- 

 serve the organs of the senses, and in some species are 

 found encasing mucus-ducts, and buried in the substance 

 of certain viscera ; as, e. ^., the heart in the bullock and 

 some other large quadrupeds. Strong membranes, called 

 "aponeurotic," and certain leaders or tendons, become 

 bony in some animals; as, e. g.^ the "tentorium" in the 

 cat, the temporal fascia in the turtle, the leaders of the 

 leg-muscles in the turkey, the nuchal ligament in the 

 mole, Fig. 41, w, and certain tendons of the abdominal 

 muscles of the kangaroo, which, so ossified, are called the 

 "marsupial bones," Fig. 44. 



For a clear and intelligible view of the osseous system 

 in general, it has become requisite to make a primary 

 classification of its parts according to their prevalent 

 position, as in the cases above cited. The superficial or 

 skin-bones constitute the system of the "dermoskeleton" 

 (from the Greek c?err/?«, skin, and sJceleton); the deep-seated 

 bones, in relation to the nervous axis and locomotion, 

 form the " neuroskeleton" (Gr. neuron^ nerve, and skeleton) ; 

 the bones connected with the sense-organs and viscera 

 form the "splanchnoskeleton (Gr. splagchnon^ viscus, or 

 inward part, and skeleton); those developed in tendons, 

 ligaments, and aponeuroses, the "scleroskeleton" (Gr. 

 scleros, hard, and skeleton). These technical terms may 

 seem harsh, and sound strange, to those commencing the 



