Introduction: Blood Cells
Blood contains several different types of cells. Some cells, such as red blood cells, carry oxygen to other cells. Other types of cells, such as white blood cells or leukocytes, provide protection from foreign cells and infectious agents. Cell fragments called platelets provide protection against bleeding. The red blood cells of different animals can have different structures.

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Still Image:
Sumatran Tiger blood
Individual red blood cells from a tiger (Panthera tigris sumatrae) appear nearly colorless when viewed under a microscope. (Images of animal red blood cells were taken at the same magnification and appear to scale).
A drop of blood (generously provided by the San Francisco Zoo) was diluted in saline solution, then sandwiched between a slide and coverslip (using a thin strip of silicon rubber as a spacer). The image was taken on an inverted compound microscope using a 40x DIC objective and a digital camera.