Dr. Murdock Head, on trial for allegedly bribing two congressmen, testified in his own defense yesterday, giving his first detailed public denial of charges against him.

Head, the director of the Airlie Foundation, acknowledged he had given money to a congressional aide, directed an assistant to wipe off money to avoid leaving fingerprints and kept a nearly $90,000 supply of cash in a safe. But Head vehemently denied his intent ever was criminal.

Head, 55, testifying before a federal jury in Alexandria, also bitterly denounced Stephen B. Elko, the former aide to Rep. Daniel J. Flood (D-Pa.) who has been a key prosecution witness in the trial. Head termed Elko a "consummate schemer-promoter" who sought to extort money from him.

Mr. Elko was like a social disease in World War II," the fast-talking, slender Airlie director asserted.

Elko has previously testified that Head gave him $49,000 in bribes between 1971 and 1974. The payoffs, Elko told the jury, were intended mainly for Flood, and former Rep. Otto E. Passman (D-La.). According to the charges against Head, the bribes were allegedly given in exchange for help from Flood and Passman in securing federal funds for Head's foundation, based in Warrenton, Va., and other ventures.

Head's 4 1/2 hours of testimony yesterday provided the first detailed rebuttal by any of the key figures in the alleged bribery scheme to charges leveled by Elko during the last two years.

Head has largely maintained a public silence since the allegations first surfaced. Flood did not testify during his bribery trial, which ended in a hung jury last February. A retrial has been delayed because of Flood's poor health.

Passman has not been charged with receiving the payoffs Elko allegedly passed on to him. He was acquitted in a separate trial of charges that he received bribes from South Korean businessman Tongsun Park.

Head, speaking in a confident tone and clipped, rapid-fire phrases, gave the jury a widely differing account of key events than had been provided by Elko.

Head testified that he was first telephoned by Elko in September 1970, shortly after the death of Eugene D. Hegarty, Flood's longtime administrative assistant. Elko, who replaced Hegarty as Flood's administrative aide, told Head at a meeting shortly afterward that Hegarty had "absconded" with Flood's campaign money, the Airlie Foundation director testified.

He [Elko] was looking for money for Flood," Head said.

The initial 1970 phone conversation with Elko led acording to Head's testimony, to several meetings during the early 1970s, during which the Airlie director gave Elko political contributions amounting to$300 to $500 each. These were markedly smaller sums than Elko testified he received from Head.

Head denied that any of these payments were intended as bribes. He also denied that he ever asked Elko to turn over any money to Passman.

On several occasions, Head testified, Elko came to Airlie, Head's sprawling, 19-year-old conference center, seeking personal financial help.

One such visit occurred in June 1972, shortly after Hurricane Agnes, according to Head's account to the jury. Elko "told me that he had lost his home" in the hurricane and that he was "destitute," Head said. He testified that he agreed to give Elko between $1,000 and $1,300.

During another meeting in August or September 1973, according to Head's testimony, Elko initially asked for a campaign donation. But then, Head said, Elko "became more pressing" in his demand for money and "talked about taxi fare." Previously, Elko testified that Head -- not Elko -- had used the term "taxi fare" to describe cash payments.

"I was not sure where this money was going when Mr. Elko got it," Head said as he recounted the 1973 meeting. He then asked an assistant for cash -- amounting to $300 to $500 -- that had been wiped clean to erase finger-prints, Head testified. His aim, he said, was to prevent his foundation and associates from becoming linked with any "unsavory" Elko transaction.

After the 1973 meeting, Head said he rejected several further appeals from Elko for money, including a 1977 request for $8,000 to $9,000 to pay legal fees.

Elko is currently on parole from a two-year sentence after being convicted of perjury and other charges in connection with an alleged bribery scheme involving a California vocational school. He has been granted immunity from further prosecution in return for his testimony against Head, Flood and others.

Head, who is also a George Washington University professor and department chairman, is charged with conspiring to arrange bribes to Flood, Elko, Passman and a now-retired Internal Revenue Service agent in exchange for help in obtaining goverment grants, contracts and favorable tax treatment for his Airlie enterprises.

He is also being tried on tax-evasion and tax-falsification charges.

Head -- dressed in a gray suit, whiteshirt and blue tie with a gold tie pin shaped like horses -- appeared calm and relaxed as he responded to questioning by one of his attorneys, Brian P. Gettings. But his responses grew testier and, at one point, his face reddened under stiff cross-examination by Assistant U.S. Attorney Theodore S. Greenberg.

"Mr. Greenberg, you're taking this completely out of context," Head shot back shortly after the prosecutor's grilling began.

Greenberg's questioning focused largely on complex tax and other financial issues. Head repeatedly replied by saying he could not recall and had kept no written record of key transactions.

At one point, Head's response prompted presiding Judge Oren R. Lewis to observe, "I'm kind of surprised that you don't know how much you put in an account -- if you put it in."

Although he acknowledged establishing a cash supply amounting to between $80,000 and $90,000, Head asserted that this was designed as a "contingency" fund intended, in part, to offset losses incurred by Raven's Hollow Ltd., a film-making company linked with Airlie. These losses included stolen camera equipment and film, Head said.

Head testified, that he instructed a former excutive assistant, Charlotte Fowler, to wipe money to remove fingerprints mainly because he needed cash that could not be traced for use in producing motion picture films about narcotics traffic and other social problems involving illicit activities.

He also said he needed money that could not be traced to Airlie to help a friend the late Dr. Amos Johnson, a former president of the Amercan academy of General Practice. Head testified that he gave Johnson money because Johnson was a victim of a "blackmail scheme."