His ideas of anatomy and physiology were extremely imperfect. Thus, he supposed the brain to be a cold spongy mass, adapted for collecting and exhaling the superfluous moisture, and intended for aiding the lungs and trachea in regulating the heat of the body. The heart is the seat of the vital fire, the fountain of the blood, the organ of motion, sensation, and nutrition, as well as of the passions, and the origin of the veins and nerves. The blood is confined to the veins; while the arteries contain an aerial spirit; and by nerves he means tendons, nerves, and arteries,--in short, strings of all kinds, as the name implies. The heart has three cavities; in the larger animals it communicates with the windpipe, or the ramifications of the pulmonary artery receive the breath in the lungs and carry it to the heart. Respiration is performed by the expansion of the air in the lungs, by means of the internal fire, and the subsequent irruption of the external air to prevent a vacuum. Digestion is a kind of concoction or boiling, performed in the stomach, assisted by the heat of the neighbouring viscera. It is perhaps impossible at the present day, when the investigation of nature is so much facilitated by the accumulated knowledge of ages in every department of physical science, by the commercial relations existing between countries in all parts of the globe, by a tried method of observation, experiment, and induction, and finally, by the possession of the most ingenious instruments, to form any adequate idea of the numerous difficulties under which the ancient naturalist laboured. On the other hand, he had this great advantage, that almost every thing was new; that the most simple observation correctly recorded, the most trivial phenomenon truly interpreted, became as it were his inalienable property, and was handed down to succeeding ages as a proof of his talents,--a circumstance which must have supplied a great motive to exertion. The History of Animals is undoubtedly one of the most remarkable performances of which physical science can boast. It must not, however, be imagined that it is a work which, replete with truth and exhibiting the well-arranged results of accurate observation and laborious investigation, is calculated to afford material aid to the modern student. To him more recent productions are the only safe guides; nor is it until he has studied them, and interrogated nature for himself, that he can derive benefit from the perusal of the treatise which we now proceed to examine. The first book contains a brief description of the parts of which the bodies of animals are composed. The introduction consists of general propositions; of which we shall present a few of the more remarkable as a specimen.