The investigation of the hereditary tendency of madness is an object of the utmost importance, both in a legal and moral point of view. Parents and guardians, in the disposal, or direction of the choice of their children in marriage, should be informed, that an alliance with a family, where insanity has prevailed, ought to be prohibited. Having directed some attention to enquiries of this nature, I am enabled truly to state, that, where one of the parents have been insane, it is more than probable that the offsprings will be similarly affected. Madness has many colours, and colours have many hues; actual madness is a severe calamity, yet experience has pointed out the treatment, and the law has permitted the imposition of the necessary restraint: but it very frequently occurs that the descendants from an insane stock, although they do not exhibit the broad features of madness, shall yet discover propensities, equally disqualifying for the purposes of life, and destructive of social happiness. The slighter shades of this disease include eccentricity, low spirits, and oftentimes a fatal tendency to immoral habits, notwithstanding the inculcation of the most correct precepts, and the force of virtuous example. In illustration of the fact, that the offsprings of insane persons are, _ceteris paribus_, more liable to be affected with madness than those whose parents have been of sound minds; it was my intention to have constructed a table, whereon might be seen the probably direct course of this disease, and also its collateral bearings: but difficulties have arisen. It appeared, on consideration, improper to attempt precision with that which was variable, and as yet unsettled; I have therefore been content to select a few histories from my book of notes, and to exhibit them in the rude state in which they were set down. _1st._--R. G. His grandfather was mad, but there was no insanity in his grandmother's family. His father was occasionally melancholic, and once had a raving paroxysm. His mother's family was sane. His father's brother died insane. R. G. has a brother and five sisters; his brother has been confined in St. Luke's, and is occasionally in a low spirited state. All his sisters have been insane; with the three youngest the disease came on after delivery. _2d._--M. M. Her grandmother was insane and destroyed herself. Her father was mad for many years, but after the birth of all his children. M. M. has two brothers and a sister; both her brothers have been insane; the sister has never been so affected, but was a person of loose character. The insanity of M. M. was connected with her menstruation; after its cessation she recovered, although she had been confined more than sixteen years.