28 



Study the preparation very carefully, recognizing (a) the Ha- 

 version systems, (b) the interstitial lamellae. In the Haversian 

 systems, note the Haversian canal, the concentric lamellae of bone, 

 the lacunae (cavities occupied during life by the bone cells), the 

 canaliculi. Understand from the development of bone, the meaning 

 of the concentric arrangement constituting an Haversian system. 

 In the interstitial bone, observe the lacunae and canaliculi. What 

 is the meaning of interstitial lamellae ? 



If desired, a tangential section of femur may be prepared to 

 show the lacunae from another aspect, and thus gain a better idea 

 of their real shape. 



37. Developing bone. l,ongisection of the hand (or foot) 

 of a fetal mammal. Fixed in ; collodion ; sections /x. 

 Stain with hematoxylin minutes ; picrofuchsin seconds. 



This illustrates endochondral ossification (early stage) and the 

 cartilaginous stage of the primary (endochondral) bones — in this 

 case the phalanges and carpal (or tarsal) bones. 



In at least one of the phalanges that is cut longitudinally the 

 early stages of ossification may be seen. Study it carefully, noting 

 the areolation of the cartilage, identifying if possible the osteo- 

 blasts and osteoclasts ; if the section is in the right plane the in- 

 growth of periosteum may be seen. If the process of ossification is 

 far enough advanced, note the formation of the primary marrow 

 cavity and the lamellae of spongy bone. The later processes of os- 

 sification are shown in 28. 



In addition the preparation illustrates : (a) true or diarthrodial 

 articulations, (6) capsular ligaments, (c) muscle and tendon, and 

 (d) developing hair. 



38. Developing bone. Longitudinal section of 

 the head of a long bone . Picric alcohol ; decalcified in 

 nitric acid decalcifier (§§ 131-132) ; collodion ; sections yu. 

 Stain in hematoxylin 30-45 minutes, picrofuchsin %-i minute. 

 Mount in balsam. 



This preparation will illustrate (a) the formation of endochon- 

 dral bone, (b) the structure of the epiphyses and the longitudinal 

 growth of a long bone. Recognize the following features : (i) the 

 center of ossification of the epiphysis, (2) the center of ossification 

 for the shaft, (3) the marrow, (4) the bone, (5) cartilage, (6) peri- 



