Perpetual rest is alone able to torture those nerves, which have been weakened by the labours of the mind; and it often quite destroys them, even in those who equally give themselves up to indolence both mental and corporeal. For the nervous system is the last work of the human machine, and if any function fails, the nerves are immediately affected; so that often from their defect, whenever it appears, there results a well-grounded suspicion of a disease in the stomach, or in some other part. They are therefore vitiated in the learned for two reasons; for, being plac’d between the mind and body, they are punish’d though innocent, let which of the two be in fault; nor do they however go unrevenged; for the injuries they suffer on one part they carry over to t’other, and thus, by a vicious circle, the mind hurts the body, and the body impairs the mind, and they with one accord injure and weaken the nerves. The seminal fluid, which has been thought by some great men not to be very different from the nervous liquor, is likewise depriv’d of its force; and upon this principle, and from an accurate consideration of what each part in a father contributes to the formation of a son, it perhaps is not badly accounted for, why strong and illustrious sons are seldom the offspring of illustrious men: for the _punctum saliens_ is contaminated at the first moment of life, whence it receives an injury which is not afterwards to be repair’d by any art; and whilst the mind of the father was entirely given up to meditation, and his corporeal functions totally neglected, the vivifying liquor was perhaps defrauded of that part of elaboration which it should have had from the brain, so as to give a proper tone to the brain of the embryo.