A broad sociological overview of the human/animal bond--by two U. of Pennsylvania professors who pioneered research in the field. Beck, an animal ecologist, and Katcher, a doctor of psychiatry, here review in detail the diverse functions pets serve in society: as companions to the elderly, co-therapists at mental institutions and prisons, precipitators of human health. They also shed light on the more subtle interrelationships. Thus, pets offer stability in a rapidly changing world; they often fill the roles of child, parent, and even family. They play with humans without competing, provide an outlet for physical affection, and ""act as a kind of living heraldry to help people proclaim the distinctiveness of their own identity."" There are many things we can learn from animals, suggest the authors, one of the most important of which is the value of non-verbal communication. Mixed in with the ample case histories and statistics are a number of clearcut, ponderable insights: ""With the older patient, the lack of sensitivity of the animal to their age, their wrinkles, their smells, and their debilitated condition provides a kind of social validation, a sustaining belief that their essential identity is unchanged and that in some real respect they are still what they once were."" With the exception of one potentially offensive chapter on failed human/animal relationships--stories of dogs devouring humans--a generally bracing as well as informing study. For a more anecdotal approach, see Betty White's Pet-Love: How Pets Take Care of Us (p. 768).