<unk>  was the method of inoculation first used to immunize individuals against smallpox (Variola) with material taken from a patient or a recently variolated individual, in the hope that a mild, but protective, infection would result. The procedure was most commonly carried out by inserting/rubbing powdered smallpox scabs or fluid from pustules into superficial scratches made in the skin. The virus was normally spread through the air, infecting first the mouth, nose, or respiratory tract, before spreading throughout the body via the lymphatic system. In contrast, infection of the skin usually led to a —but, crucially, still induced immunity to the virus. The patient would develop pustules like those caused by naturally acquired smallpox. Eventually, after about two to four weeks, these symptoms would subside, indicating successful recovery and immunity. The method was first used in China, India, parts of Africa and the Middle East before it was introduced into England and North America in the 1720s in the face of some opposition. The method is no longer used today. It was replaced by the smallpox vaccine, a safer alternative. This in turn led to the development of the many vaccines now available against other diseases.
Variolation
Dominance 
Penetrance
Cordance
Involution 
Deformity
Concept creep
Latent inhibition