Skulls of twenty-one animals. Drawing, c. 1789.

On p. 99 of the text, Lavater writes of the "proportional difference of force and form" throughout nature. "From the insect invisible to the naked eye, up to the elephant, is not the gradation of internal and external character perpetually in exact relation". Further, on p. 102 he declares that "the generic difference between man and animals is obviously manifested in the bony system ... [In animals] the head is affixed to the backbone, has no greater extent than is necessary for the action of the vital parts", which explains the relative paucity of expression in the face of an animal