Further, the nature of the delusion must be analysed. Why is it of this and not of that persecution? Why is this particular person feared or hated? Is it a constant factor in the patient’s existence, or does it break out at certain times? If so, the patient’s life at these critical periods must be carefully examined. The doctor must discover where the patient was at the time, what he was doing and thinking, who were his companions, and so on. Next comes the important inquiry into the history of the delusion. And here, just as the anatomist is able nowadays to mobilise for service all his knowledge of comparative anatomy and evolution, so if the physician has really scientific knowledge, not only of the delusions in other patients, but also of the development of ordinary beliefs in sane people,[37] he will be immensely helped in his search, and may be enabled thereby to make many short cuts to the essential facts. He will endeavour to date the important stages of development of the delusion; to find a time when, so far as the patient knows, his mind was free from it. Thus we may say that a psychological investigation of a case of mental disorder dissects its normal as well as its abnormal phenomena into their functional elements. Compared with the procedure which merely records such gross units as delusions or hallucinations, it is as anatomy to mere carving, however skilful the latter may be. But the psychological investigation is not merely comparable to anatomical dissection. We have also compared the mind to a chemical compound, rather than a mechanical mixture. Especially is this true not only of the normal but also of the abnormal mind, when the latter has had time to settle down into its new position of relative equilibrium and integration; when, for example, a delusion has become so fixed that the patient’s life is entirely ordered in obedience to it, and he has ceased to have any doubts as to its reality or to struggle against its domination.[38] It is only when the warring elements in the mind are relatively independent, and before they have succeeded in “making terms” with each other, that the mind even remotely resembles a mechanical mixture. It follows, therefore, that psychological analysis of a case of mental disorder is usually comparable to _chemical analysis_ as well as to anatomical dissection. Now the most striking result of chemical analysis is to show that the appearance and general properties of the elements composing a compound are different from the appearance and properties of the compound itself. This is exactly the case, too, with mental analysis. A mere dissection of an abnormal condition is sometimes sufficient in the milder cases to serve as the basis for curative measures,[39] but in more advanced cases, or those of longer standing, real analysis is necessary in order to get at the unknown factors.