syphilitic psychoses, twenty per cent manic-depressive insanity, fourteen per cent dementia praecox, and seven per cent epilepsy. Statistics at that time were not available on purely psychopathic conditions, owing to the classification used. In discussing the etiology of shell shock Col. Salmon divides those conditions into four groups—1. Cases in which death is caused by exploding shells or mines without external signs of injury; 2. Those in which severe neurological symptoms follow burial or concussion by explosions, with characteristic syndromes suggesting the operation of mechanical factors; 3. Cases in which there may or may not be damage to the central nervous system, but showing neuroses similar to those of civil life—"In this group of cases, in which there is possibility but no proof of damage to the central nervous system, the symptoms present which might be attributable to such damage are quite overshadowed by those characteristic of the neuroses;" and 4. Cases in which even the slightest damage to the central nervous system from the direct effect of explosions is exceedingly improbable. He also found that hundreds of men who have not been exposed to battle conditions at all develop symptoms almost identical with those described as "shell shock," many occurring in the non-expeditionary forces. The psychogenic factors involved are very well summarized by Col. Salmon in the following words:—"The psychological basis of the war neuroses (like that of the neuroses in civil life) is an elaboration, with endless variations, of one central theme: escape from an intolerable situation in real life to one made tolerable by the neurosis. The conditions which may make intolerable the situation in which a soldier finds himself hardly need stating. Not only fear, which exists at some time in nearly all soldiers and in many is constantly present, but horror, revulsion against the ghastly duties which must be sometimes performed, intense longing for home, particularly in married men, emotional situations resulting from the interplay of personal conflicts and military conditions, all play their part in making an escape of some sort mandatory. Death provides a means which cannot be sought consciously. Flight or desertion is rendered impossible by ideals of duty, patriotism and honor, by the reactions acquired by training or imposed by discipline and by herd reactions. Malingering is a military crime and is not at the disposal of those governed by higher ethical conceptions. Nevertheless, the conflict between a simple and direct expression in flight of the instinct of self-preservation and such factors demands some sort of compromise. Wounds solve the problem most happily for many men and the mild exhilaration so often seen among the wounded has a sound psychological basis. Others with a sufficient adaptability find a means of adjustment. The neurosis provides a means of escape so convenient that the real source of wonder is not that it