212 VERTEBRATES 



and the cochlea find three articulating bones, the hammer, 

 anvil and stirrup which convey the sound from the outer 

 to the inner ear. Of what pecular value is the external 

 ear? In different parts of the skull note small openings 

 through which nerves pass from the brain. These are 

 foramen. A prominent one is seen on the inner surface 

 of the eye socket. 



(2) — The Spinal Column — (a) Identify the following 

 divisions of vertebrae: cervical (neck), the thoracic (rib- 

 bearing), the lumbar (without ribs), the sacral (united ver- 

 tebrae of pelvis), and caudal, or tail. Count the number 

 of vertebrae in each. Study the ribs in the thoracic region 

 and compare them with the projections or transverse pro- 

 cesses of the lumbar vertebrae. Of what value are the 

 ribs ? The processes ? Why would it not be better to have 

 ribs the entire distance? 



(b) Remove the vertebra bearing the sixth pair of ribs 

 by cutting through the cartilaginous joints. Find the cen- 

 trum, the neural arch containing the spinal cord, the ribs, 

 and the cartilage which unites the ribs with the sternum. 

 Study the cartilaginous packing at each end of the ver- 

 tebra. Of what use is it? Does the rib grow out of the 

 vertebra? Is it movable? Explain the attachment. What 

 is the advantage or disadvantage of having movable ribs? 

 Study the attachment of the ribs to the sternum. What is 

 the nature of the sternum? Is it divided into segments? 

 How many ribs are attached to it? Sketch the sternum 

 with its attachments. Make drawing of the typical seg- 

 ment just studied (Xi)- 



(c) Remove the fifth vertebra of the lumbar region. 

 Study as before the centrum, neural arch, and the neural 



