The author takes as his text the recent experiences of the Russo- Japanese war, in which, according to the testimony of numerous witnesses, outbreaks of acute insanity were extremely common in the battlefield, and occasionally assumed an epidemic character, and in which, moreover, many “regrettable incidents” were due to mental disorders in commanding officers. Dealing first with the statistics of suicide and of insanity in the army in time of peace, he points out that the former phenomenon is very much more frequent amongst soldiers than amongst the general population in the chief European countries. In Italy in 1901, while the suicide-rate for the whole country was about.061 per mille, in the army it amounted to “33 per mille. And it appears to be tending to increase; thus the figures for the years 1895 to 1901 show that, while sanitary improvements have reduced the general mortality in the army by nearly a half, the ratio of suicide has slightly risen. On examining the figures in detail it is seen that the suicide rate is very high during the first year of service, that it falls off some what in the second year, to rise again when the period of service is prolonged over two years. With regard to insanity, the official statistics would suggest that it is less frequent amongst soldiers than in the population at large, but the author contends that this result is misleading, inasmuch as the army represents a picked population which by reason of its age, constitution, and the exclusion from its ranks of the congenitally defective, is, or ought to be, specially free from insane tendency. In any case the rate of insanity in the Italian army is increasing notably of recent years. With regard to officers, there is a consensus of opinion in all countries that the incidence of insanity amongst them is peculiarly high, and this applies more particularly to general paralysis, which is estimated to account for 50 per cent, of mental disease in German officers, for 54 per cent, in French, and for 55 per cent, in Italian.