This is an excellent monograph on growth and development, with especial reference to the rôle of the endocrine glands in these processes. Years ago the authors did some good pioneering experimental work in this field, especially on the rôle of the thyroid and the thymus in growth. In this monograph the entire literature is covered in a thoroughly critical review. The list of references occupies forty-four pages. The gaps in our knowledge are indicated. At present the weakest link is the rôle of the thymus. The author calls the thymus a "growth gland." If this is so, it probably applies at least for mammals only in the early stages of interuterine life, when accurate experimental attacks on the problem are difficult. The monograph will be useful to internists, pediatricians and biologists.