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As the western states of America were settled, pioneers often had to drink rancid water from ponds and other sources. This often resulted in chronic diarrhea, causing many cases of dehydration and death that could have been avoided if clean water had been available.
Intradermal injections are somewhat difficult to correctly administer because the skin layers are so thin that it is easy to accidentally punch through to the deeper subcutaneous layer.
More than one-third of adult Americans are obese. Diseases that kill the largest number of people annually, such as heart disease, cancer, diabetes, stroke, and hypertension, can be attributed to diet.
In 1835 it was discovered that a disease of silkworms known as muscardine could be transferred from one silkworm to another, and was caused by a fungus.
Only 12 hours after an egg cell is fertilized by a sperm cell, the egg cell starts to divide. As it continues to divide, it moves along the fallopian tube toward the uterus at about 1 inch per day.