i74 
ANIMAL ACTIVITIES, 
How is the lower jaw suspended from the skull ? 
Separate the back-bone, or vertebral column, into 
parts (vertebrae). Are the vertebrae near the tail like 
those near the head ? Study particularly one of the 
vertebrae 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 haemal arch, and the spine 
attached to it the haemal spine. This arch protects 
the dorsal aorta. Are there any ribs present ? 
Using one of the vertebrae 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. 
( b ) 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. 
(<?) Brain of fish with nerves. 
(/) End view of a vertebra from near the tail. 
(g) End view of a vertebra above the visceral cavity. 
(h) 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 vertebrae 
gives this class its name. This back-bone furnishes a 
