Final answer:
The person who was seriously hit by a member of Congress was Senator Charles Sumner, who was attacked by Representative Preston Brooks with a cane in 1856 over a speech Sumner gave against slavery.
Step-by-step explanation:
The specific incident you are referencing seems to be the caning of Senator Charles Sumner by Representative Preston Brooks in 1856. This event took place in the United States Congress and became known as Bleeding Sumner.
After Sumner gave a strong speech against slavery, including insults directed at a relative of Brooks, Brooks retaliated by violently beating Sumner with a cane. The assault was so severe that Sumner was unable to return to his Senate duties for several years.
In the Southern states, Brooks was considered a hero for this act, receiving gifts of canes bearing inscriptions such as "Hit Him Again" and "Use Knock Down Arguments."
In the North, however, the event turned Sumner into a martyr for the antislavery cause and was indicative of the divide between the pro- and anti-slavery factions in the country. The incident contributed to the increasing tensions that eventually led to the Civil War.