| Description |
Examines the transport systems of various types of animals and observes both open and closed circulatory systems, explaining that larger animals have internal circulatory systems consisting of blood vessels and a pump or heart. Compares the heart structures of the earthworm, clam, insect, axolotl, turtle, rat, and fetal pig. Emphasizes that single-celled organisms transport materials by the streaming of cytoplasm and diffusion, and uses live specimens and drawings to show that the structure of hydra and planaria permits rapid exchanges of gases.
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