INTRODUCTION 19 



displayed to a large number of students, have been embodied in the 

 demonstrations. A brief list of experiments of this kind is given on 

 pages 227, 228. 



While it is difficult to perform physiologic experiments in accordance 

 with a definite time-schedule, the material embodied in this book has 

 been arranged in such a way that each lesson will require about three 

 hours for its completion and each demonstration one hour, making a 

 total of one hundred and eighty hours. At the end of each period a 

 few minutes should be set aside for a review of the work performed. 

 Special attention should at this time be paid to those students who have 

 failed to observe and formulate the essential facts and principles to be 

 derived from any particular lesson. It would be a pedagogically un- 

 sound principle to call the attention of the students to these facts before- 

 hand, because introductory explanations tend to rob the student of the 

 pleasure of independent investigation and thought. If the work in 

 physiology is well balanced and co-ordinated between the class-room 

 and the laboratory, preliminary talks pertaining to the general bearing 

 of the different experiments are actually worse than useless. Such 

 discussions should concern themselves more particularly with matters 

 closely related to the methods and apparatus, so that the student may 

 be in a more favorable position to avoid mistakes in his technic. I have 

 endeavored to aid him in this regard by supplying him with this 

 laboratory guide, amplified, for the reason just stated, with explana- 

 tions bearing directly upon the experiments. 



R. BURTON-OPITZ. 

 Columbia University, 

 May, 1920. 



