CONNECTIVE TISSUES I/ 



protect vital organs in the skull and trunk and acts as levers 

 which are worked by the muscles in the limbs. The tissue 

 is characterized by the deposit of calcareous or lime salts 

 within its intercellular substance, to which its well-known 

 hardness is due. Most bones may be divided into an outer 

 layer of compact bone and an inner layer of spongy or can- 

 cellated bone. 



FIG. 15. Transverse section of compact bony tissue (of humerus). 



Three of the Haversian canals are seen, with their concentric rings; also the 

 lacunae, with the canaliculi extending from them across the direction of the 

 lamellae. The Haversian apertures were filled with air and debris in grinding 

 down the section, and therefore appear black in the figure, which represents 

 the object as viewed with transmitted light. The Haversian systems are so 

 closely packed in this section that scarcely any interstitial lamellae are visible. 

 X 150. (Kirkes after Sharpey.) 



Microscopically bone is seen to consist of numbers of os- 

 seous layers or lamellae, arranged as, (a) circumferential la- 

 mellae which are arranged parallel to the inner and outer 

 surfaces of the bone, (b) Haversian lamella which are ar- 

 ranged concentrically around the Haversian canals and (c) 

 interstitial lamella, which are arranged irregularly so as to 



