Spallanzani and others have viewed the subject as it regards physiology, but with such results as left the field open to subsequent investigation. Dr. Edwards seems to have seized upon the deficiencies of his predecessors, and, by going over their ground, and extending his own inquiries, he has arrived at most interesting and important results. These he has divided into four parts, as they relate to the different orders of the animal creation. The first part includes some of the lower animals, particularly tenacious of life, and of cold blood, such as frogs, toads, and salamanders. The second part is devoted to other animals of cold blood, and of the vertebrated order, as fish, and those reptiles which include lizards, snakes, and turtles. The third part refers to warm-blooded animals; and the fourth part of the work is dedicated to the influence of the physical agents upon the human race and vertebrated animals. To these the author has added the discoveries of modern times, relative to electricity on the animal economy, in an Appendix. A collection of tables is appended to the work, exhibiting the principal series of his experiments, as they regard the relative influence of physical agents on the duration of life, and the phenomena resulting from their mutual action. The great importance of the four grand divisions of the work forbids our hastily reviewing them, and we will endeavour to condense so much of the information they contain as may forward the objects of our analysis. Dr. Edwards thus announces the arrangement of his work:— “Ces recherches auront donc rapport à l’air dans les conditions de quantité, de mouvement et de repos, de densité et de raréfaction; à l’eau liquide et à la vapeur aqueuse; à la température, dans ses modifications de degré et de durée; à la lumière et à l’électricité. Ces causes agissent à la fois sur l’économie animale, ordinairement d’une manière sourde et imperceptible; et toujours [p140] l’impression qu’on reçoit est le résultat de toutes ces actions combinées.” “Lors même que, par l’intensité de l’une d’elles, il nous arrive de distinguer la cause qui nous affecte, l’observation de l’effet se borne le plus souvent à la sensation, et les autres changemens qui l’accompagnent nous échappent. On conçoit par la que l’observation la plus attentive des phénomènes tels que la nature nous les présente, ne saurait démêler dans cette combinaison d’actions l’effet propre à chaque cause, ni reconnaître des effets qui ne seraient pas révélés par la sensation.