INTRODUCTION. Vll. 



logical preparation, or the neat accomplishment of a graphic record, 

 yields immediate satisfaction to a student biologically inclined. He 

 is dealing directly with the animal, and the result seems an end in 

 itself. It is otherwise with tests and estimations carried out as 

 mere exercises. The interest of a quantitative result, which may 

 be great when it is obtained during an actual study of metabolism, 

 seems remote to the student who works without any such stimulus. 

 Yet in large chemical classes it is almost impossible to provide 

 closer touch with the animal, and interest cannot always be secured 

 by maintaining an exact correspondence in the sequence of lectures 

 and classes. It is desirable therefore that, even in a book with aims 

 that are avowedly practical, there should be some judicious reference 

 to theory and to the actual significance of results. In the present 

 work this end seems to be reached without undue consumption of 

 space. 



The book in its present form, while very fully covering the 

 ground required by the medical student, can be profitably used by 

 all who seek for accurate and full descriptions of biochemical 

 methods, whether for use in medical diagnosis or in biological 

 researches. The earlier editions of the book have been used by the 

 students at the Agricultural Laboratory here, and in its present 

 form it would appear to be highly suited to the needs of those 

 engaged in the study of animal nutrition. 



F. GOWLAND HOPKINS. 



BIOCHEMICAL DEPARTMENT, 

 CAMBRIDGE. 



