A celebrated professor of anatomy has asserted, that we could not tell, by reasoning _à priori_, that the body was mortal, so intimately woven with its texture are the principles of life. Lord Bacon declares, that the only cause of death which is natural to man, is that from old age; and complains of the imperfection of physic, in not being able to guard the principle of life, until the whole of the oil that feeds it is consumed. We cannot as yet admit this proposition of our noble philosopher. In the inventory of the grave in every country, we find more of the spoils of youth and manhood than of age. This must be attributed to moral as well as physical causes. We need only recollect the custom among the Indians, of sleeping in the open air in a variable climate; the alternate action of heat and cold upon their bodies, to which the warmth of their cabins exposes them; their long marches; their excessive exercise; their intemperance in eating, to which their long fasting and their public feasts naturally prompt them; and, lastly, the vicinity of their habitations to the banks of rivers, in order to discover the empire of diseases among them in every stage of their lives. They have in vain attempted to elude the general laws of mortality, while their mode of life subjects them to these remote, but certain causes of diseases. From what we know of the action of these powers upon the human body, it will hardly be necessary to appeal to facts to determine that FEVERS constitute the only diseases among the Indians. These fevers are occasioned by the insensible qualities of the air. Those which are produced by cold and heat are of the inflammatory kind, such as pleurisies, peripneumonies, and rheumatisms. Those which are produced by the insensible qualities of the air, or by putrid exhalations, are intermitting, remitting, inflammatory, and malignant, according as the exhalations are combined with more or less heat or cold. The DYSENTERY (which is an Indian disease) comes under the class of fevers. It appears to be the febris introversa of Dr. Sydenham. The Indians are subject to ANIMAL and VEGETABLE POISONS. The effects of these upon the body, are in some degree analogous to the exhalations we have mentioned. When they do not bring on sudden death, they produce, according to their force, either a common inflammatory, or a malignant fever. The SMALL POX and the VENEREAL DISEASE were communicated to the Indians of North-America by the Europeans. Nor can I find that they were ever subject to the SCURVY. Whether this was obviated by their method of preserving their flesh, or by their mixing it at all times with vegetables, I shall not undertake to determine. Their peculiar customs and manners seem to have exempted them from this, as well as from the common diseases of the skin.