In a less degree the destructive passion directed against objects, or figuratively against institutions, known as _iconoclasm_, is often a mere outburst of unreasoning emotion. Its energy is misdirected and fruitless. What was the result of that which during the eighth and ninth centuries raged in Constantinople and Asia Minor? It altered image-worship into picture-worship, nothing more. 2. CONDITIONS OF ASTHENIA.—In contrast to the repeated explosions of nerve force which give rise to the active motor states of ethnic dementia I have been considering, are those characterised by a loss of reaction to stimuli, by passive, merely sensory, conditions. These are of two varieties, well marked in their differences, each highly significant in its ethnological and historic relations. The one is allied to melancholia, being marked by depression or inaction of the psychic forces, the other by their exhaustion, by incapacity for reaction to ordinary stimuli. _(a) Melancholia._—The consequence of mental shock, I have already pointed out, is to bring about a sort of mental paralysis, a listless, apathetic state; and this I have illustrated by some examples. A touching one is recorded of the Greek colony which erected the city of Pæstum on the Tyrrhenian Sea, whose stately ruins still attract thousands of visitors annually. A clearly ethnic type of melancholia is _nostalgia_ or homesickness. Of course it is found in some degree in all lands, but with some peoples, notably dwellers in high northern latitudes, the Lapps and Eskimo, it is severe and general. If removed from their surroundings they mope and die. _(b) Neurasthenia._—Diseases of nervous and mental exhaustion belong exclusively among nations of advanced culture. There are those which have not merely increased, most of them have originated in stages of high civilisation; not, as some have falsely argued, from conditions essential to culture, but to errors and misdirections in that culture. As, in all rapid motions, slight deviations entail more serious consequences than when motion is slow, so, in the rapid progress of modern times, slight neglects of hygiene bring about more serious results than in ruder countries. This explains the relative increase of some forms of insanity, of suicide and criminality, and the appearance of new maladies, such as progressive paralysis, in civilised centres. They are due to exhaustion of the nerve centres in those who are not adapted to bear the strain of contemporary competitive life, or who, if able, fail to direct their activities in successful channels.