110 
Water is made up of oxygen and another gas 
called hydrogen. But water also contains air dissolved 
in it. When water is boiled, it loses its air, and until it 
dissolves more air marine animals, like fishes, can not 
live in it. 
Experiments will be made in order to prove these 
statements. 
The Breathing of Animals. 
Most large animals that live on the land breathe by 
means of lungs. Oxygen is taken into the substance of 
the body, and carbonic acid gas is given out. Plants also 
breathe in oxygen and give out carbonic acid gas. 
Marine animals obtain their oxygen from the sea water by 
means of gills mstead of lings. 
Second Day. 
The Structure of a Fish. 
The stomach, the liver and the digestion of the food. 
The blood, heart and gills; the circulation of the 
blood through the body. 
The red blood of a fish consists of a clear colourless 
liquid, in which there are a great number of small reddish, 
oval particles, about 5,4, part of an ineh in diameter. 
These are the corpuscles, and their use is to carry the 
oxygen to the tissues of the animal. 
The heart is a force-pump, which propels the blood 
all through the body. From the heart the blood goes to 
the gills, where it takes in oxygen from the water, and 
gets rid of its carbonic acid gas. It then flows in the 
blood vessels all through the body. 
The brain, the nerves and the senses. 
The Breeding of a Fish.— Fishes are either male 
or female, but with the exception of the skates, rays, 
