The proposition will no doubt be accepted by all whom I address (although the public is so slow to recognise it) that the only sound test of the increase of insanity is to ascertain the number of occurring cases of Mental Disorder in proportion to the population during the periods of time we desire to compare. Most of the mistakes made upon this subject have arisen from taking existing cases of insanity at different epochs, thus totally overlooking the effect of accumulation arising from the fact that although the annual admissions may be stationary, the discharges from recoveries and deaths will fall far short of them. This in any case. But when we compare successive periods, still assuming that the admissions remain the same, the ratio of discharges and deaths may vary so greatly at different epochs that the degree of accumulation will be largely affected, being more or less according to the proportion of recoveries and the rate of mortality.