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Autoimmune diseases occur when the immune system destroys its own healthy tissues. When this occurs, white blood cells cannot distinguish between pathogens and normal cells.
The most common childhood diseases include croup, chickenpox, ear infections, flu, pneumonia, ringworm, respiratory syncytial virus, scabies, head lice, and asthma.
Throughout history, plants containing cardiac steroids have been used as heart drugs and as poisons (e.g., in arrows used in combat), emetics, and diuretics.
Bacteria have flourished on the earth for over three billion years. They were the first life forms on the planet.
Acetaminophen (Tylenol) in overdose can seriously damage the liver. It should never be taken by people who use alcohol heavily; it can result in severe liver damage and even a condition requiring a liver transplant.
![Coronary artery bypass graft (CABG). The grafts are often obtained from the patient’s saphenous vein](https://biology-forums.com/gallery/47/medium_14755_11_11_12_7_15_45_100282437.jpeg)
![Electrocardiography. (a) Electrodes are placed on the patient’s chest to record the electrical event](https://biology-forums.com/gallery/47/medium_14755_11_11_12_7_15_46_100311063.jpeg)