CBS, not unlike other networks, gets generous with informational programming once the May sweeps are over and TV viewing falls off. Last week CBS aired a Walter Cronkite special; on June 26, it will premiere two new prime-time news half-hours with Charles Kuralt and Bill Moyers; and tonight, at 8 on Channel 9, the network offers a "Body Human" science special that may have been sitting on a shelf for ages.

Networks--phooey!

"The Living Code," like other specials of the species "Body Human," has its troubling snags. Ostensibly a report on the burgeoning field of genetics, the program ignores controversial areas like genetic engineering and eschews the traditional documentary form to present three "case studies" that are essentially short TV movies enacted by the actual participants.

The case studies don't always relate clearly to the matter of genetics, but the last of the three, the story of a 9-year-old New Jersey boy named Billy Brown, who died of leukemia and its complications, is undeniably moving. Because of a "genetic twist of fate," Billy's leukemia did not respond to chemotherapy, and doctors decided his only chance for survival was bone marrow transplants. Billy's sister was the marrow donor.

Crucial organs in the boy's body rejected the marrow and, we learn, he died, although the script rules the case "victoriously a stepping stone to the day children will live." The "Body Human" specials always try to personalize the medical problems they survey (and inevitably praise the medical community to the skies; doctors are among the producers), and this involves intrusions, presumably welcome by the subjects, on the intensely emotional moments of real people. The camera is there when Billy's parents are told their son will die and the father says, "He'll always be with us."

The program also pays a visit to a Little Rock, Ark., couple who, faced with the distinct possibility of a genetic defect in their offspring, decide to have a baby by artificial insemination, using the sperm of an anonymous donor. This is all discussed as casually as if they were picking out an end table at a furniture store.

Certain scenes in these "case studies" look like, but are not labeled as, reenactments--especially during a sequence on genetic detective work that helps identify the murderer of a 25-year-old woman. The producers throw in everything but a light show to keep a viewer's attention: fetal photography, which has now become commonplace on these shows and others; Rich Little doing a Bogart impression; dancing teen-agers; and what have you.

As always with "Body Human" specials, narrator Alexander Scourby is saddled with a script (by Louis H. Gorfain and coproducer Dr. Robert E. Fuisz) slippery with superlatives. He speaks of "wonders," "splendors," "marvels," uses adjectives like "joyous," "marvelous," "daring," "astounding," and adverbs like "incredibly" "amazingly" and even "fascinatingly." Well it all is pretty fascinating, and even amazing, but it would be nice if The Body Viewer were allowed to discover that for himself. "Body Human" specials always sound like ad copy for the human race. To whom is it for sale? And who would want it?