The female population was doubtlessly subdivided in an analogous manner, for it is expressly recorded that all marriageable girls were kept in four different houses. Those of the first class, qualified as “the white virgins,” were dedicated to the service of the Creator, the Sun and the Inca; the second were given in marriage to the nobility; the third class married the Curacas or civil governors, and the last were qualified as “black,” and pertained to the lower classes. Caste division was never lost sight of—indeed one Inca went so far as to order that all the people of the Below “should flatten the heads of their children, so that they should be long and sloping from the front.” Thus they should ever be distinguishable from the nobility and “yield them obedience.” Although it is not expressly stated, it may be inferred from actual specimens of skulls which have been found that, in some localities, in order to differentiate the two classes still more, members of the nobility strove to mould the heads of their children in a high peak, so that they too should perpetually bear the mark of their rank. Whether such a procedure would exert a correspondingly elevating or abasing influence upon the intellectual development of the two classes is a problem for anthropologists. A very simple explanation of the reason why artificial deformation of the skull was ever adopted, is obtainable when the all-powerful dominion of a certain set of ideas is recognized. Many other customs, still in practice amongst American tribes, are likewise explained by the arbitrary division of population into classes and categories. The Peruvian custom of bestowing one name upon a child when it was one year old and another when it attained maturity is the direct outcome of the classification of individuals by age. The ceremonial observances which accompanied the bestowal of these names were accompanied by a change of costume which constituted the official enrolment or advancement into another class. The existence of further systematic class-distinctions is proven by the description of the picturesque ceremony performed in the month of August at Cuzco and called “the driving out of sickness.” In the centre of the great square around the urn of gold which typified the “central fountain” (precisely the idea expressed by the name of Mexico), four hundred warriors assembled. One hundred, representing one of the four ayllus, faced towards each cardinal point and subsequently ran at full speed in its direction, crying “Go forth all evils!”