ANATOMY AND PHYSIOLOGY. 157 
oxidized, and fat is produced. In the next stage of 
insect life the respiration is still lower, but, as no food 
is now supplied, the store of fatty matter is acted on 
by the oxygen, and is partially used in the formation 
of the tissues of the future insect. In the last stage, 
when the insect comes out perfect, the respiratory 
organs awake from a state of almost inaction to a 
degree of activity unparalleled in the Vertebrate 
classes. There is henceforth no production of fat, 
except under very peculiar circumstances, when, for 
this purpose, the respiratory process is checked. A 
familiar instance of this occurs in the economy of 
the honey-bee, which instinctively suspends the me- 
chanical processes of life, and shuts out the influence 
of the air, while the sugar in her stomach is being 
changed into wax. ‘This change, which we can 
interpret, but cannot imitate in our laboratories, is a 
simple process of chemical deoxidation.* 
With this and a few such like exceptions, the 
chief end of digestion, in the perfect insect, is to 
supply materials for the present repair of the mus- 
cular system, for the peculiar glandular secretions of 
the species, and for the substance of the future 
embryo. The wear and tear of the nervous system, 
and of the digestive system itself, are comparatively 
very small items; and that of the skin and bones 
counts for nothing at all. There is no elaborate 
system of one gland preparing materials for another ; 
the very simplicity of the whole arrangement bafiles 
our means of research. The whole process is trans- 
acted in one vessel, whence the few organs which 
need it select their own nourishment directly. Bile, 
* Honey-sugar = Cyp Hy, Oj4. Wax = Ogo He2 03. 
