Edward Jenner inferred that a person who once had small pox cannot have it once again. So something is there in these persons which grows after the initial infection which interferes with the secondary infection resisting it.
<h3><u>Explanation:</u></h3>
Edward Jenner is called the Father of Vaccination. Jenner noticed that the milkmaids who deal with the cows all the time don't generally suffer from the cowpox or small pox. Then as an Experiment, he took some sample from the pustules of the cow having pox and then cleaned it and injected the sample into a healthy child. Then when everyone of the locality suffered from the same disease, that child remained healthy. So that lead to infer that there are something in the pustule which lead to resist the secondary infection of this disease. So this lead to the invention of vaccines.
Scientists collect information that allows them to make evolutionary connections between organisms. Similar to detective work, scientists must use evidence to uncover the facts. In the case of phylogeny, evolutionary investigations focus on two types of evidence: morphologic (form and function) and genetic.
