THE BONES.. 13 



A. The posterior articular process is the projection by which 

 the vertebra joins the next vertebra below. 



i. Is there a medullary cavity in the vertebra ? 



j. Is there any spongy bone ? 



k. Does an irregular bone, then, have a medullary cavity 

 or spongy bone ? 



I. Sketch a side and an end view of a vertebra. 



2. Compare with the dorsal vertebra the following : 



a. The axis, or second cervical (neck) vertebra, of the 

 human skeleton or of a sheep. The odontoid process is the 

 rounded prominence upon it. 



b. The atlas, or first cervical vertebra. 



c. What parts are present and what parts are wanting 

 in each? 



d. Place the axis in position on the atlas and find the 

 use of the odontoid process. 



e. Sketch an end view of each. 



D. The Chemical Composition of Bone. 



Materials. A thin piece of bone about two inches long. Hydro- 

 chloric acid, ten per cent. Ammonium hydrate. A long, slender 

 bone, as a rib of a chicken. 



Apparatus. A pair of Fairbanks standard scales. Bunsen burner. 

 A piece of wire gauze about six inches square. A tall, slender jarr 

 A ring-stand. 



All bones are composed of animal and mineral matter. 



I. THE MINERAL MATTER. 



a. Weigh carefully a clean piece of bone. 



b. Burn it on a piece of sheets-iron over the flame of a 



