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. Nutt all. 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 111 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. 
Cornell University, 
January, 1915. 
Wm. A. Riley. 
0. A. JOHANNSEN. 
