In the practice of scabs from smallpox victims were used to immunize susceptible individuals against smallpox.

Variolation

Explanation:

Variolation can be defined as the condition in which the inocolutaion of the individuals with the infectious materials, scabs or pulses from the smallpox victim.

This was introduced by the route of nasal passage or injected intravenously. The infection that developed because of this was less than normal and it provided protein against more serious disease.

Hence, the correct answer is Variolation.

1 digestive system

2 stomach

3 bladder

4 carbon deoxide

5 tiger