Answer:
Miasma theory was replaced because John Snow collected data that showed that germs cause disease.
Explanation:
The theory of miasma was proposed in the past when some scientists —like doctors Thomas Sydenham and Giovanni Maria Lancisi— thought that disease was the product of emanations originated by the decomposition of organic matter. This theory was based on the fact that diseases predominated in places with poor hygienic conditions.
John Snow, an english physician, was one of the main contributors to the microbial theory of disease. In 1854, while a cholera epidemic was occurring, he collected data and organized it statistically and then concluded that the disease was caused by germs present in drinking water. This data was contrary to the miasma theory, which would eventually be displaced by the microbial theory of the disease.
