CBS News anchor Dan Rather today spent his third day on the witness stand in a $30 million slander suit against himself and the network, staunchly defending the integrity of a "60 Minutes" segment on insurance fraud.

Rather and CBS have been named in the suit filed by a California physician, Dr. Carl A. Galloway, over a "60 Minutes" segment that was broadcast in December 1979.

Rather's cross-examination by Galloway's attorney, Bruce Friedman, has involved a series of tedious skirmishes. One of today's sparring matches focused on whether Rather believed Galloway shared in the profits of a clinic that was the focus of the "60 Minutes" segment.

Friedman kept putting the question, variously worded, to Rather. Rather kept repeating that Galloway, in testimony, "didn't deny that he worked at the clinic. He didn't deny he made money out of the clinic . . . and has never denied that the clinic's business was to turn out phony medical reports."

Friedman asked once again if Rather believed Galloway shared in the clinic profits, and Rather finally replied: "If it looks like a duck and walks like a duck and quacks like a duck, you've got a duck."

Friedman then asked if "this philosophy" of Rather's was "the basis of the entire show." Rather replied that it was a figure of speech.

Friedman then asked: "The fact that Dr. Galloway looked like a duck and walked like a duck and quacked like a duck--is that the reason you never bothered to confront him?"

Rather replied that he had left a message at the clinic for Galloway, with a telephone number where Galloway could reach him. After leaving the clinic, Rather said, he went with his producer, Steve Glauber, to a pay phone where Glauber called another office where Galloway worked, and left another message for the doctor, stressing its importance.

Viewers who watched the "60 Minutes" segment, "It's No Accident," saw Rather leave his phone number for Galloway with a clinic, receptionist and then remark: "And if you believe he's going to call me, you believe rocks grow."

Rather testified today that other than Glauber making one more call to each of the numbers they had for the doctor, no further effort was made to contact Galloway.

In the 1979 segment, Rather, then a correspondent for the popular news magazine program, showed his "60 Minutes" audience a phony medical report CBS investigators had obtained and said, "It was signed by Carl A. Galloway, M.D."

In his suit, Galloway claims his name was forged on the report, which was obtained from a clinic where Galloway was employed three days a week. Galloway says, however, he no longer worked at the clinic when CBS got the report.

Rather, in his testimony, often referred to the clinic where the report was obtained as "Dr. Galloway's office." Los Angeles Superior Court Judge Jack W. Swink overruled each of Friedman's many objections to this phrasing.

Often, Friedman put a question to Rather again and again, arguing that the answer was not responsive, and Rather kept repeating his original answer, sometimes inserting, "I'm trying to be responsive to your question, Mr. Friedman."

Today was expected to be Rather's last day of testimony. Closing arguments could begin late Wednesday.