516 POPULAR SCIENCE MONTHLY 



from that excellent master, Miiller afterward spoke in the most grate- 

 ful terms, and declared that it was through the influence and example 

 of Rudolphi alone that his own scientific pursuits were afterwards 

 turned so fully in the direction of comparative anatomy. 



At the expiration of his two years of labor, and immensely en- 

 riched in all the fields of natural science, Miiller again returned to 

 Bonn, and in 1824 was enrolled as academic lecturer in comparative 

 anatomy and physiology. Two years later, when but twenty-five years 

 old, he was made professor extraordinary in the same branch of science. 



The epochs in his activity in investigation which immediately fol- 

 lowed upon his return to Bonn have well been called by DuBois Bey- 

 mond the subjective physiologico-philosophical period. The literary 

 landmarks of this period in Miiller's career are two works : First, " On 

 the comparative physiology of the sense of sight in men and animals, 

 with researches on the motions of the eyes and on the sight of man " ; 

 second, " Concerning the phantasmal phenomena of vision : a physio- 

 logical research dealing with the physiological evidence of Aristotle 

 concerning dreams, the philosophies and the arts." 



In the former of these two works we find recorded that excellent 

 discovery that the sight of insects (which possess facet-eyes) must be 

 conceived of as a mosaic interpretation of objects; that is, the pictures 

 which the insects themselves see are placed together as in the form of 

 a mosaic. In the second work regarding the " Phantasmal Phenomena 

 of Vision," Miiller took up a study, the idea of which reached far back 

 into his earliest youth, when he was accustomed to give free play to 

 his fancy in imagining strange shapes and figures on the plaster- 

 scarred walls of the old buildings. These fanciful appearances, which 

 thus early became so familiar in the imaginings of his boyhood, he 

 submitted in maturer years to searching philosophic scrutiny; and the 

 work in which they are described and discussed is a charming yet 

 masterly application of experiment in anatomy, physiology, physics 

 and psychology. Through the medium of these scientific principles 

 Miiller explained the seeing of devils and spirits; the friar, who, after 

 long hours of supplication, sees the desired consecration in the form 

 of a shining cloud; the superstitious, to whom the tempter appears 

 as an evil spirit: these phenomena were for Miiller only the results 

 of the passion-aroused conditions in the material substances of their 

 sight. 



Of all Miiller's labors at this time, greatest importance must be 

 attached to his work in elucidation of the laws of the specific energy 

 of the sense organs. With ingenious experiment he worked out the 

 general law that, in whatever manner a sense organ may be stimulated, 

 it always answers to our consciousness by the method peculiar to it. 

 It was from these and other related investigations that Miiller deduced 

 many of his philosophical principles: For instance, that we can not 



