When the error is universal, it is supposed to end. The adoption of the foundling establishes its consanguinity.
Misconception was especially brought in by describing descent in terms of "blood". The common speech uses expressions such as consanguinity, pure-blooded, half-blood, and the like, which call up a misleading picture to the mind. Blood is in some respects a fluid, and thus it is supposed that this fluid can be both quantitatively and qualitatively diluted with other bloods, just as treacle can be diluted with water.