The fourth edition of the premier book on animal law covers a rapidly developing field that is exponentially increasing its presence in both the public eye and on the list of desired classes for law students. In the past fifteen years, the number of animal law classes in American law schools has gone from less than ten to more than one hundred, and this casebook has been used as a model for courses internationally. Animal law is, in its simplest (and broadest) sense, a combination of statutory and decisional law in which the nature?-?legal, social, or biological?-?of non-human animals is an important factor. This new edition of Animal Law: Cases and Materials contains significant reorganization and updating while continuing to present a cohesive format that touches on many areas in which animals affect legal doctrines, caselaw, and legislative direction. Because animal law is not a traditional legal field, the book is largely framed according to traditional legal headings such as tort, contract, criminal, and constitutional law. Each chapter sets out cases and commentary where animal law is developing its own doctrine. In this fourth edition, the text has been updated and several chapters reorganized and revised to provide even greater clarity than in earlier editions. An important chapter on the commercial use of animals, introduced in the third edition, has been updated with more recent cases and statutory developments covering the significant areas of agriculture and biomedical research.