An unlikely, not to say embarrassing subject--the iconography of Christ's genitals--treated with insight, erudition, wit, and urbane good taste. The study is based on the Lionel Trilling seminar that art historian Steinberg (U. of Pennsylvania) gave at Columbia in 1981; and in general it reads like an expanded lecture. It argues, first, that explicit attention to the genitals of Christ in Renaissance paintings and other images is quite common (nearly 1,000 examples, mostly in Nativity scenes); second, that this emphasis represents a whole-hearted celebration of Christ's humanity (his divinity being taken for granted); and third, that later generations obscured this positive (and perfectly orthodox) vision of the Incarnation by painting over the offending parts or misreading the painters' intentions. (The gesture of St. Anne fondling her divine grandson's groin in a picture by Hans Baldung Grien is interpreted by the leading expert on Baldung as a ""miracle-working spell,"" etc.) Steinberg's thesis, then, is rather simple, but he enriches it with 246 well-chosen illustrations (which include one remarkable ""Man of Sorrows"" by Maerten van Heemskerck [ca. 1525] with a bulging erection) and a fluent commentary, both aesthetically and theologically acute, that matches pictorial epiphanies of Jesus' vulnerable but salvific human flesh with similar themes in contemporary sermons and devotional literature. Steinberg pads his book by appending to it 39 brief excurses (all of them informative, and some, like his survey of the ""chin chuck"" in Western art, brilliant bits of explication). This creates a certain repetitiousness, but, as Steinberg says, it serves to strengthen a case bound to meet with initial incredulity. Solid scholarship moving gracefully across a vast frame of reference.