XIX 



STRUCTURES CONCERNED IN THE PRE- 

 SERVATION OF THE INDIVIDUAL, OR 

 TO ITS ADVANTAGE. 



A. 



ENDOSKELETON. 



(Including all structures that function as an Endoskeleton, 

 whether derived from Ectoderm, Mesoderm, or Endoderm, 

 or the equivalent embryonic layers.) 



A structure specialized to give to the organism support, 

 strength, rigidity, and protection to more deeply seated parts ; 

 in some cases it furnishes the levers and fulcra for the move- 

 ments of parts of the body or advantageous attachment for 

 muscle. Its physical properties are independent of life. 



Plants. 



The bundles of thick-walled elongated cells commonly asso- 

 ciated with the vascular bundles act as an endoskeleton. 



Animals. 



As spicules, fibres, &c. As cartilage. White fibrous tissue, 

 the bundles closely interwoven to resist strain in any direction, 

 with or without an admixture of yellow elastic tissue. Bone or 

 allied tissue hardened by lime-salts. 



After taxonomically arranged endoskeletons is a group of 

 air-containing bones. 



B. 



FLEXIBLE BONDS OF UNION AND SUPPORT. 

 VERTEBRAL COLUMN. JOINTS. 



Areolar tissue and yellow elastic tissue, connecting and sup- 

 porting soft parts. Bonus of union between rigid structures, 

 ligaments, &c. Physical properties are independent of life. 



