The more experience the specialist in mental diseases has, the less liable he is to give an opinion that will assure friends of the patient that relapses may not occur after any form of disturbed mentality. While this is true in mania, {214} it is almost more generally admitted with regard to melancholia. Most patients who have one attack of severe depression of spirits will surely have others if they are placed in circumstances that encourage the development of melancholic ideas. Any severe emotional strain will be followed by at least some symptoms of greater depression than would be expected from the normal person under the same conditions. Professor Kraepelin has pointed out that in about one out of six cases the patients who came to him supposedly for the treatment of primary attacks of melancholia proved to be really suffering from a relapse of severe mental depression. The careful investigation of the history of these cases showed that they had suffered from previous attacks of depression, though sometimes these were so slight as not to have attracted any special attention from the medical attendant,--if indeed one had been called in the case--and at times even failed to occasion more than a passing remark on the part of friends with whom the patient was living. The most frequent form of idiopathic insanity is melancholia. The disease is characterised by depression of spirits. Professor Berkley's definition, besides being scientifically exact, is popularly intelligible. According to him, "Melancholia is a simple, affective insanity in persons not necessarily burdened by neuropathic heredity, characterised by mental pain which is excessive, out of all adequate proportion to its cause, and accompanied by a more or less well-defined inhibition of the mental faculties." This latter part of the definition is extremely important. In extreme cases patients are able to accomplish no other mental acts beyond those which concern the supposed cause of their depression. Their lack of attention to other things is the measure of the mental disturbance. Their minds constantly revolve about one source of discouragement. They become absolutely introspective and their surroundings fail utterly, in pronounced cases, to produce any reaction in them. In milder cases this involves an increasing neglect of whatever occupation the patient may have, solely for the purpose of giving up time to the contemplation of the cause of his depression. It is not easy always to recognise the limits between a {215} depression of spirits that is not entirely abnormal and a corresponding state of mind that is manifestly due to insanity. When misfortunes occur, individuals will be mentally depressed. Sorrow has in it necessarily no element of mental alienation. It is only when it becomes excessive that observers realise that there is disturbance of the mental faculties, causing the undue persistence and the exaggeration of the grief.