The hospital added expansions to two wings of the Bulfinch Building in 1846 and 1847. This was largely because of population growth in Boston since the hospital had opened, including immigrants fleeing the famine in Ireland. Mass General was the city’s only major hospital at the time. After the first successful public demonstration of surgical ether anesthesia took place in the hospital’s operating room in 1846, the hospital also noticed an increase in the number of surgical patients. Indeed, the availability of anesthesia made many patients much more willing to undergo needed operations.