THE BONES. 15 



/. Where is the mineral matter ? Prove it. 

 g. Burn this as you did the entire bone. What previous 

 experiment does this verify? 



E. The Microsgojnoil Structure, of Bone. 



Material. A prepared slide showing a cross-section of a human 

 humerus. 



Apparatus. A compound microscope. 



Examine under the microscope a prepared cross-section 

 of a long bone, as the human fibula or humerus. 



a. Notice with the low power : 



1. The large Haversian canals that are cut across. 



These are the passages for the blood-vessels. 



2. The lamellae, or layers arranged concentrically 



around the cajials. 



3. The lacunae, or small cavities separating the 



lamellae. What is their shape ? These were 

 once filled with living cells. Why are they 

 now black? 



4. Sketch. 



b. Notice, in addition, with high power : 



1. The canaliculi, or wavy branches which run across 



the lamellae . 



(1) Where do they lead ? 



(2) What is their use ? 



2. Sketch. 



