80 PHYSIOLOGY OF THE HONEY-BEE. 
not contractible. Each room of the heart presents, on 
either side, an opening for the returning blood. The blood, 
‘¢ soaking through the body’’ (Cheshire), comes in contact 
with the air contained in the tracheal ramifications, where it 
is arterialized, or in plainer words, renovated, before com- 
ing back to the heart. 
The bee is not provided with any discernible blood or 
lymphatic vessels save the aorta, and its blood is colorless. 
70. The breathing organ of the bee is spread through its 
whole body. It is formed of membranous vessels, or tra- 
chez, whose ramifications spread and penetrate into the 
organs, as the rootlets of a plant sink down into the soil. 
Connected with these, there is, on each side of the abdomi- 
nal cavity, a large tracheal bag, variable in form and dimen- 
sions, according to the quantity of air that it contains. 
Bees breathe through holes, or spiracles, which are placed 
on each side of the body, and open into the tracheal bags 
and. trachez. 
V1. “The act of respiration consists in the alternate dilatation 
and contraction of the abdominal segments. By filling, or emp- 
tying the air-bags, the bee can change her specific gravity. 
When a bee is preparing herself for flight, the act of respiration 
resembles that of birds, under similar circumstances. At the mo- 
ment of expanding her wings, which is indeed an act of respira- 
tion, the spiracles or breathing holes are expanded, and the air, 
rushing into them, is extended into the whole body, which by 
the expansion of the air-bags, is enlarged in bulk, and rendered 
of less specific gravity ; so that when the spiracles are closed, at 
the instant the insect endeavors to make the first stroke with, 
and raise itself upon, its wings, it is enabled to rise in the air, 
and sustain a long and powerful flight, with but little muscular 
exertion.” * * ¥* “Newport has shown that the develop- 
ment of heat in insects, just as in vertebrates, depends on the 
quantity and activity of respiration and the volume of circu- 
lation.”—(Packard, Salem, 1869.) 
72. Mr. Cheshire notices that bees, even in full, vigor- 
ous youth and strength, are not at at all times able to take 
