Picasso's animal prints owe much of their immediacy to the lift-ground aquatint technique that Vollard's printer, Roger Lacourière, had taught to Picasso in 1936.  This technique preserved the marks of Picasso's brushwork and even the impress of his fingers with which he had textured the ram's wool.

Like many of Vollard's projects, L'Histoire naturelle was left unpublished at his sudden death in 1939.  It was completed by his associate, Martin Fabiani, three years later.