The swimmer swims everyday. He swims day after day. One day, he disappears into the sea. Memory, says C, has been defined by the ancients as of two kinds, one natural, the other artificial. He gives a reference as to where the ancients have made this statement, namely in 'the chapter on memory.' 'Natural memory,' he continues, 'is that which a man receives in creation or generation, and according to what influence receives from the reigning planet, according to which we see that some men have better memories than others. ''The other kind of memory,' he continues, 'is artificial memory and this is of two kinds.' One consists in the use of medicines and plasters for the improvement of memory, and these he does not recommend. The other kind consists in frequently going over in memory what one wishes to retain, like an ox chewing the cud. For as it is said in the book of memory and reminiscence by frequent repetition (memory) is firmly confirmed.'