PREFACE. 



Our investigations into the properties and toxic action of tlie vcnona of 

 Heloderma were undertaken at the request of Dr. S. Weir Mitchell, and carried 

 out with the aid of grants from the Carnegie Institution of Washington. 



In order to be able to extend the researches in various directions, I asso- 

 ciated with myself a number of collaborators, who undertook the study of 

 various parts of the problem. If, notwithstanding this partition, the work 

 has, as I hope, preserved its uniform character, it is due to the fact that by 

 far the greater part of these investigations was carried out in the Laboratory 

 of Experimental Pathology of the University of Pennsylvania, of which I had 

 charge at that time. This made possible the constant correlation of the 

 results, and the data obtained in the study of one problem became available 

 for and were used in the investigation of other problems. The chemical 

 analysis of the venom which Doctor Alsberg undertook was done elsewhere. 

 The histological study of the changes produced by the venom in the central 

 nervous system was partly done in the Laboratory of Neuropathology of the 

 University of Pennsylvania, through permission of Dr. W. G. Spiller. 



Dr. D. T. MacDougal, Director of the Department of Botanical Research 

 of the Carnegie Infstitution of Washington, on various occasions kindly obtained 

 for us living specimens of Heloderma suspecium. 



To Dr. S. Weir Mitchell and to the Smithsonian Institution we are 

 indebted for a specimen of Heloderma horridum. 



I am under obligation to Doctor Calmettc, of the Pasteur Institute of 

 Lille, who very kindly put at my disposal some of his cobra antivenin. 



I wish to thank all my collaborators for their faithful cooperation, and 

 especially to acknowledge the assistance given me in the preparation of this 

 work on various occasions by Dr. Moyer S. Fleisher and Dr. Ellen P. Corson- 

 White. 



Leo Loeb. 

 Barnard Free Skin and Cancer Hospital, 

 St. Louis, Missouri, March 1912. 



