14 ELEMENTS OF COMPARATIVE ZOOLOGY. 



Pick into the side of the tail until the backbone (vertebral 

 column) is reached. Take out a small piece of it and clean 

 it by boiling a few minutes. . Wash away the flesh, and see 

 that it is made up of a series of bones (vertebrae), arranged 

 one after the other. Examine a single vertebra, making out 

 the following parts: (1) A body or centrum, shaped like an 

 hour-glass and hollow at either end, (amphicoelous). Do 

 the hollows of the two ends connect ? (2) Arising from 

 the centrum two bony plates (neural processes), uniting 

 above into a single neural spine. These together form a 

 neural arch; so-called, since the great nervous (neuron, 

 nerve) structure, the spinal cord, passes through it. (3) 

 On the opposite or ventral side of the centrum a similar 

 haemal arch, composed of haemal processes and haemal spine. 



Examine in the same way a vertebra in the trunk region. 

 Can you find the same parts ? Do the ribs correspond to 

 neural arches or to haemal arches, or are they something 

 different from either ? 



Draw a front view of trunk and caudal vertebrae, 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 (Jiaima, 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 ex- 

 posed. Enlarge the opening by picking, and then with 

 great care pull away the loose gray matter which covers the 



