PEEFACE TO THE SECOND EDITION. 



IN no department of biology have the advances of 

 recent years been more marked than in that which is 

 studied under the name of physiological or biological chem- 

 istry. While the subject has always been regarded as im- 

 portant in the study of the vital processes, its value is 

 being more than ever emphasized as fundamental in a 

 biological or medical education. A revision of this man- 

 ual, with the addition of new material, has therefore seemed 

 advisable. No change has been made in the original plan, 

 but suggestions arising from its use in this university or 

 from the experience of the author's colleagues have been 

 adopted wherever they promise to add to the success of 

 the work. For such suggestions particular thanks are due, 

 among others, to Dr. D. W. Fetterolf, of the University of 

 Pennsylvania, and Dr. Paul Bartsch, of Howard Univer- 

 sity. 



ELBERT W. KOCKWOOD. 



THE UNIVERSITY OF IOWA, 

 1906. 



(iii) 



