THE GRECO-ROMAN PERIOD 103 



which was very popular in the Middle Ages. Zoology, 

 on the contrary, came to a standstill. Already in 

 the second century, an unknown author, surnamed 

 Physiologus, had foreshadowed by his fabulous and 

 mythical descriptions of animals the Bestiary litera- 

 ture, and his work had a great influence on the animal 

 decorations of the Middle Ages. In this period we 

 must also mention Alchemy, to which we shall have to 

 return and of which Zosimus, about the year 300 a.d., 

 summarizes the knowledge, sometimes fantastic, some- 

 times useful, relating to the working of metals. 



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