28 LABORATORY WORK. 



Examine in the same way a vertebra in the trunk 

 region. Can you find the same parts? Do the ribs 

 correspond to neural processes or to haemal processes, 

 or are they something different from either? 



Draw a front view of trunk and caudal vertebra?, naming 

 the parts. 



In another bit of the back-bone, near the head, see 

 the spinal cord passing through the neural arch. Can 

 you find any nerves given off from it? How are they 

 arranged? 



In the tail region see blood-vessels passing in a similar 

 manner through the haemal arch (haima, blood). Pull 

 apart two vertebrae and see what fills the cavities in the 

 ends. 



Cut off the head,* and after picking away the muscles 

 at the hinder part of the skull above, carefully slice off 

 the top of the skull with a strong knife, taking only thin 

 slices and exercising great care after the cavity of the 

 skull is exposed. Enlarge the opening by picking, and 

 then with great care pull away the loose gray matter 

 which covers the white or pinkish brain. When this is 

 exposed make out in it the following parts, beginning in 

 front : 



(1) The olfactory lobes tapering in front into the nerves 

 going to the nostrils (p. 24). 



(2) Two rounded oval masses (cerebral hemispheres) 

 meeting in the middle line in front, and together constitut- 

 ing the cerebrum. 



(3) The 'twixt-brain, also two-lobed, but lying at a 

 lower level. 



(4) The large, paired, rounded optic lobes. 



* These steps are best taken with the decalcified skull (p. 22). 



