O.D. Simons, 57, of Lubbock, Texas has not eaten for two years. Instead, he is nourished by chemicals that are pumped into his bloodstream by an apparatus he wears all his waking hours. The device, invented by Dr. Stanley Dudrick of Houston, is cumbersome, and its menu hardly compares with a steak dinner. But without it, Simons, who has had cancer of the bowel, would almost surely be dead.

Nearly 100 patients at the University of Texas Medical Center are undergoing similar nutritional therapy. Each owes his survival to Dr. Dudrick, who in 1972, at the precocious age of 37, became head of the center's department of surgery.

Dudrick was turned from a fledgling cardiac surgeon into a pioneer nutritionist one day when he was an intern in Philadelphia. "We had three patients who had gone through successful surgery—but they all died," he recalls. "I was terribly discouraged. Then the chairman of the surgery department said that, if I analyzed it, I'd see they really died of starvation. They couldn't eat, and they didn't have enough reserve tissues to draw on. I was too dumb to make that observation myself."

Dudrick immersed himself in the study of how to provide food for those who can't eat. From 10 to 40 percent of hospital deaths are still caused, he believes, by malnutrition. Patients with gastrointestinal cancer are especially vulnerable, as well as those with kidney or liver failure or burn trauma.

Sir Christopher Wren experimented with intravenous feeding of dogs as early as the 17th century. In its modern traditional form (most familiar in the glucose drip bottle), it cannot support life for long, however. Dudrick solved the problem by developing a complete nutritive compound. But he faced another obstacle: "We couldn't put it in through the arm because the mixture was too thick and produced problems in the small veins. We couldn't thin it down with water either, because that produced edema, or excess fluid in the connective tissue.

"Then," Dudrick says, "we hit on the idea of putting it into larger veins, where the blood flow is so great that the nutritional substances would be diluted and rushed throughout the body." Often the compound is pumped into the superior vena cava, through a catheter threaded through a smaller vein near the collarbone.

Dudrick's nutrient, specially mixed for each patient, is composed of some 40 substances, including amino acids, glucose, vitamins and minerals. In some cases druggists or patients themselves can prepare the mixture.

Total Parenteral Nutrition (TPN) is Dudrick's term for his technique. (Parenteral refers to bypassing the intestines.) In 1964 he astounded a medical convention in Germany with the news that he had raised six beagle puppies entirely on TPN for 287 days. In 1966 he first tried it on six humans with apparently terminal illness; all recovered and four are still alive. Since then Dudrick has used TPN on about 6,000 patients and has received two American Medical Association awards.

Eldest of four children of a Nanticoke, Pa. coal miner turned insurance agent, Dudrick decided on a medical career after watching the family doctor pull his mother through a near-fatal illness. Both his sisters are nurses. Still a crusader, he worries that, while half the nation's doctors are aware of TPN, only five percent are using it. "It takes time," he says, "for doctors to accept so much responsibility for dealing with such complex advances in human chemistry, metabolism and nutrition."

Success will depend on campaigning for the technique, while simplifying it. "Someday we'll have TPN down so that it will commonly be done in a general practitioner's office," Dudrick predicts. "That's what I'm hoping for. I want to leave something better behind when I go, rather than just practice medicine the way it has always been done."