ABSTRACT
The investigation of the contents of images which follow each other in spontaneous succession, produced the three, or five, laws of reproduction which have been reduced to one or two. The qualitative investigation of the reproductive processes is as yet scarcely begun; in fact it is hardly recognized as a special problem. On the other hand, quantitative investigation in the special case of voluntary impression has been abundantly investigated. H. Ebbinghaus was the pioneer here, while G. E. Muller critically examined and extended Ebbinghaus's ideas.
