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Wood first appeared in plants called progymnosperms.
Persian leopard (Panthera pardus ciscaucasica), also called Caucasian leopard
Endocarditis. The human heart has been sectioned to reveal the left ventricle and origin of the aort
Photograph of the flea that transmits Yersinia pestis to cause bubonic plague, called the oriental r
Pneumonia. This common lung inflammation may be caused by bacteria, viruses, or fungi and is often d
James A. Garfield lies mortally wounded. After failing to locate the bullet, surgeons called in Alex