Two cheers for Herriott's new one; The Lord God Made Them All, by James Herriott. New York: St. Martin's Press. $ 13.95.

To several million people in the world (speaking many languages) comes the joyful news of another book by James Herriott, the Yorkshire veterinarian. It follows a series: "All Things Bright and Beautiful," "All Creatures Great and Small," and "All Things Wise and Wonderful," completing the 19th-century verse by Cecil Frances Alexander with the new title "The Lord God Made Them All."

But to this abject aficionado, the latest book is a disapointment. James Herriott has returned from World War II, his veterinary practice resumed.Many changes have taken place. Siegfried and Tristan Farnon, his alter egos of the earlier books, have married and are following their own careers, and James's two young children are not quite substantial enough to take their placeS.

Perhaps one is being too greedy. But to lose any of the previous goodies -- the richness of Yorkshire life, the tenderness and humanity that shaped Herriott's relations with man and beast, is to lose qualities unexpendable. Of course, Herriott is here, and he is a dear man of endless patience, resourceful love, and tireless night journeys to inaccessible farms, but the book is made up of odd bits and pieces, remembered scrappily in most cases, and frequently without the rich patina that made living legends of his earlier tales.

His journeys -- as attendant to a shipload of costly sheep, to the Soviet Union, and his commensurate service to a cargo airplane of Jersey heifers consigned to Turkey -- are fun but without his usual perspicacity. The writing is uneven and, alas, frequently banal. The new veterinary world to which he returned is exploding with new drugs, and their use is explained in great detail.

But in spite of all these caveats there is still the brimming love, the vast respect for the courage of the upland farmers, Herriott's humility when confronted by a farmer's faith that works when the medical skill fails.

The chapter on Jack, who loved every creature on his farm whether two-legged, four-legged, or winged and who wanted all "to have a chance" no matter what the odds, is worth the price of the book. Jack, thankful for "Mr. Herriott's kind help" was unwilling ever to give up. No faith was too small, no difficulty too threatening, no patience too demanding, if the lame sheep walked again and the dying cow stood on her feet, by means beyond medical art.

James Herriott has so enlarged our understanding and love of animals that the debt is considerable even when the book is less than one might hope.