VI Preface 



They wish to express indebtedness to the authors and publishers 

 who have so willingly given permission to use certain illustrations. 

 Especially is this acknowledgment due to Professor John Henry 

 Comstock, Dr. L. O. Howard, Dr. Graham-Smith, and Professor 

 G. H. T. Nuttall. Professor Comstock not only authorized the use 

 of departmental negatives by the late Professor M. V Slingerland 

 (credited as M. V. S.), but generously put at their disposal the illus- 

 trations from the Manual for the Study of Insects and from 

 the Spider Book. Figures 5 and iii are from Peter's "Der Arzt 

 und die Heilkunft in der deutschen Vergangenheit." It should be 

 noted that on examining the original, it is found that Gottfried's 

 figure relates to an event antedating the typical epidemic of dancing 

 mania. 



Wm. a. Riley. 

 Cornell University, O. A. Johannsen. 



January, 1915. 



