The Life Processes of the Individual 
151 
RESPIRATION 
That an animal may live, it must have oxygen. The 
oxygen taken into the body in respiration does not go to 
form protoplasm in the various cells but it is used to com¬ 
bine with the products of katabolism to make simpler com¬ 
pounds which can be eliminated from the body. These 
products of the breaking down of the living substance are 
of such a character that they poison the cells unless they 
are promptly removed. The process is like ordinary com¬ 
bustion in that these products combine with oxygen to 
form carbon dioxid and water and to generate heat. 
In man, the oxygen is taken into the lungs and the blood 
is pumped there to meet the oxygen. But the bee does not 
have a closed circulation which will effectually carry the 
blood to the oxygen. Furthermore, the higher animals 
have in their red blood corpuscles a substance, haemoglobin, 
which is capable of absorbing abundant oxygen, but this is 
lacking in the colorless blood of insects. In the bee, instead 
of the blood being carried to the oxygen, the oxygen is 
carried to the blood by means of tracheal sacs and a multi¬ 
tude of tracheal branches which go to every organ and to 
every part of the bee’s body. These tracheae receive their 
air supply through openings in the outer wall, the spiracles, 
two pairs on the sides of the thorax and eight pairs on the 
abdomen. The tracheae are composed of a delicate epi¬ 
thelium lined with a thin layer of chitin. To prevent the 
collapse of the tracheal trunks, some of them are further 
strengthened with spirally placed rings of chitin, which 
are thickenings of the chitin lining. The finer branches 
lack these chitin rings and there are few heavy trunks in 
the bee, the walls usually being delicate. 
The oxygen is therefore carried to all parts of the bee’s 
body, passes through the walls of the tracheal system, is 
absorbed by the blood and is carried to every cell. The 
products of katabolism are in turn carried by the blood, 
and the water vapor (at least most of it) and the carbon 
