VI 11 PREFACE. 



of them are taken from preparations kindly presented to me by 

 my friend Professor Swaen of Liege. I am greatly indebted to 

 my demonstrator, Arthur Clarkson, M.B., C.M., for a considerable 

 number of the drawings, and also to my pupil, Mr. C. E. M. Lowe, 

 for similar services. A few of the drawings were made by myself. 

 To F. W. Stansfield, M.B., Ch.B. (Viet.), my thanks are due for 

 assistance in reading the proof-sheets. 



I have also to express my obligations to several scientific in- 

 strument makers and others, including Messrs. Zeiss, Hartnack, 

 Verick, Leitz, Keichert, Jung, Hicks, Eternod, Zimmermann, 

 Hume, Beck, Swift & Son, Gardner, and A. Eraser. 



Finally, I have to thank my publishers for the liberal manner 

 in which the work is illustrated. 



WILLIAM STIRLING. 



PHYSIOLOGICAL LABORATORY, THE OWENS COLLEGE, 

 MANCHESTER, 



