174 ANIMAL ACTIVITIES. 
How is the lower jaw suspended from the skull ? 
Separate the back-bone, or vertebral column, into 
parts (vertebra). Are the vertebre near the tail like 
those near the head? Study particularly one of the 
vertebrzee near the tail. The main part of a vertebra 
is the centrum. Is the centrum entirely solid? What 
is its shape in a longitudinal section after removing all 
soft parts? Sketch front and side view of a vertebra, 
and a longitudinal section. 
Do you find the cavity for the spinal cord? Call 
this cavity the neural cavity, and the processes at- 
tached to the centrum and enclosing the neural cavity, 
the neural arch, and the spine above it the neural 
spine. Is this spine dorsal or ventral? Does it 
point towards the anterior or the posterior part of the 
body ? 
Do you find the cavity for the passage of the large 
blood-vessel ? Call this the hemal arch, and the spine 
attached to it the hemal spine. This arch protects 
the dorsal aorta. Are there any ribs present? 
Using one of the vertebrz above the visceral cavity, 
find how it differs from a vertebra near the tail. 
Summary of Drawings. (a) Side view of fish with 
fins extended. 
() Side view of head of a fish showing as many parts 
as possible. 
(c) Gill of a fish showing parts. Heart of fish with 
arteries and veins. 
(d) Cross-section of the body of a fish a little in front 
of the anal opening. Sketch of alimentary canal. 
(e) Brain of fish with nerves. 
(/) End view of a vertebra from near the tail. 
(g) End view of a vertebra above the visceral cavity. 
(2) Longitudinal section of a vertebra. 
Vertebrates. The study of a fish introduces us to 
the class Vertebrata of the sub-kingdom Chordata. 
The possession of a back-bone made up of vertebra 
gives this class its name. This back-bone furnishes a 
