Vice President Bush was acting president for about eight hours while President Reagan was under anesthesia for his colon operation. But he was not the first stand-in in U.S. history; once, the country even went without a president for a day.

In 1792, Congress passed a law designating the president pro tempore of the Senate and the speaker of the House to succeed the president and vice president.

In 1820, President James Monroe and Vice President Daniel Tompkins were elected to a second term. Because their inauguration date fell on Sunday, March 4, the two decided to wait until the following Monday to take their oaths, but their first terms ended at noon on that Sunday. Therefore, John Gaillard of South Carolina, the president pro tem of the Senate, became president for a day.

In 1849, the inaugural again fell on a Sunday, March 4, and President-elect Zachary Taylor decided to take the oath of office on Monday. However, this time there was no official Senate president pro tem. The office had been held by Missouri Sen. David Atchison, but the Senate adjourned a day earlier.

Since Atchison could not legally return to that position until March 5, and James K. Polk was no longer president after noon, March 4, the country was without a president for one day.

There are other similarities between Reagan's operation and those of other presidents, but open news coverage is not one of the similarities. When President Grover Cleveland had an operation almost a century ago, the press was told that he was vacationing on the Hudson River, and the public did not find out about it for almost a year, an Ohio State University professor said.

Rob Rupp, an assistant professor of American history, said Cleveland underwent minor surgery on a cancerous growth in his mouth during his second term in office, (1893-97).

"It's quite a contrast to how things are done today," Rupp said in a telephone interview with United Press International. "Today you see Reagan's intestine on the front page . . . , in Cleveland's time, the public was unaware of the operation until about a year later."

The secret operation took place on a houseboat on the Hudson River, Rupp said. The public was told that the president was vacationing on a houseboat between New York City and Albany, N.Y.