If, therefore, it is found, as is in fact the case, that all writers, who either inquired into the matter with really scientific precautions, or had to do with pure, primitive material, inform us that, speaking broadly, the sexual relations were strictly regulated; and on the other hand, all settlers, casual observers, and people who obviously had already corrupted blacks under observation, speak of unrestricted immorality and even of incest,[34] it may be safely said that the second type of statements refer to degenerate blacks. Here the general _a priori_ suppositions quite harmonize with what is to be found in the evidence; the second type of statements may be therefore fittingly discarded. In the same way it may be assumed that with a general dissolution and corruption in the aboriginal society, and with all kinds of vices engrafted upon it the general level of conjugal affection and the standard of treatment of the wife by her husband went down. The contrary cannot possibly be assumed. [34] See below, the statements, pp. 92 _sqq._ So it appears that, even from the quality of the material the observer had at his disposal, some useful hints may be obtained as to the direction in which our statements need correction. Furthermore it was said above that useful indications can be gathered from the way in which the observer was in contact with the natives; whether the observer was a long time in contact with the natives or only a short time; whether he made his observations with deliberate scientific aim, or whether they were made casually and recollected afterwards; whether he had good opportunities for observation, and under what conditions this was carried on, and so forth.