PREFACE vii 



ligations and I wish that it might soon be translated 

 into English. I take pleasure also in expressing my 

 thanks to my colleagues, Professors Conklin and 

 Smyth and Dr. Mayer for valuable suggestions in 

 the difficulties of treatment and to Dr. W. J. Sinclair 

 for his care in making the figures. 



W. B. S. 



PRINCETON, N. J., December, 1916. 



