He shows us in his lib. de naturalib. facultat. that, out of the humours, all the parts are formed, and these parts are either _similar_ or _dissimilar_; i. e. simple or compound. Bone is a similar part, that is, it is a simple part; so is an artery, or vein, or ligament. Each of these is so constituted, as that it has a predominance of one element in its nature; and it is therefore dry, or cold, or moist, &c. But if an adust element be, by accident or disease, accumulated in a part naturally cold, the function of such part is morbidly affected. The natural tendency, however, of similar humours to unite, causes each part to receive its regular supply; a principle which BICHAT has since characterized as, _contractilite organique insensible_. To show the wonderful simplicity of the Galenical system, which for plainness and easy attainment may be compared with the improved nomenclature of chemistry, we will cite a passage from ARGENTERIUS, who, perhaps, was as learned in this kind of lore as any man of his time. In his Tractatio de calidi significationibus, he says; "If any body would undertake to give a general enumeration of those circumstances, in which this term calidum and the others (frigidum, humidum, &c.) are applicable to the explanation of this warmth, he shall find truly, that they are the elements, the humours, the parts, the whole body, medicines, food, air, climate, the weather, the season of the year, and even ages; for these all are either temperate, or hot, or cold, or humid, or dry." The animal body is moved and governed by two principles; one of them corresponds to the _vie animale_ of BICHAT, and the other to the _vie organique_. Since the power of sensation and of voluntary or elective motion, says he, is a property of animals, and since that of growth and nutrition is common both to animals and plants; the former may be called attributes of the soul, and the latter attributes of nature. Whence we say, that animals are governed by the soul and by nature, while plants are governed by nature alone. The powers of the body are faculties; and these are either natural, vital, or animal: but they are so subdivided, that we have as many faculties as there are sorts of action. Under the class of natural faculties, we find three principal sorts; to wit, a facultas generatrix, an auctrix, and a nutrix. But if you ask, says GALEN, how many faculties there be, which result from the action of these on each other, you will find them as numerous and diverse as there are numbers and diversities of the animal parts. For example, we have an attractrix faculty, a retentrix, alteratrix, expultrix, &c. &c., all of which are variously modified, according to the nature of the similar or dissimilar parts they are exercised in, or, in other words, according to the nature of the tissues or organs, in which they reside.