INTE OD UCTION 1 9 



ings in his notes, either unwillingly or dependently frequently 

 both. The laboratory work is thus robbed of much of the benefit 

 it is intended to give the student. Independence and originality 

 are completely defeated or aborted, except in the case of the rare 

 student. 



If the laboratory manual contains graphic records of experiments, 

 much of the time of the demonstrator will be consumed in explaining 

 to the students why the same physiological functions observed with 

 slightly different apparatus and under slightly different circumstances 

 may yield tracings which differ in minor detail from those in the 

 book. The energies of both demonstrator and students will thus 

 be partially diverted from their legitimate channel. 



If there are no tracings in the text, students will naturally, by 

 comparison of their tracings, discover the essential and the non- 

 essential features and will seek the cause of the essential features 

 of their tracings. After the student has made these independent 

 discoveries he is in a position to gain the maximum profit from the 

 comparison of his own tracings with those which others have taken, 

 and from any explanations which the demonstrator may choose 

 to add. 



It is evident, then, that, from a pedagogical standpoint, the labo- 

 ratory guide should be sparsely illustrated. On the other hand, 

 the student's notes should be profusely illustrated. 



Regarding Explanations. It may be well to introduce this topic 

 by a statement of what the function of the demonstrator is not. It 

 certainly is not to rob the student of the pleasure, exhilaration, and 

 benefit of the independent investigation of a problem by introducing 

 each laboratory period with an enumeration of the facts and prin- 

 ciples which the work of the day is expected to establish. Such an 

 introduction is worse than useless. The desirability of even asking 

 the attention of the entire class to introductory remarks on the gen- 

 eral bearing of the problem in hand is to be questioned. If the 

 problem is well chosen and the work in the physiological laboratory 

 properly co-ordinated with that in the recitation room and lecture 

 room and that in the other departments, its significance will be at 

 once evident to the intelligent pupil. If the introductory talk is 

 omitted the prompt student may begin at once, upon entering the 

 laboratory, the problem of the day, and will have a clear gain of ten 

 or twenty minutes. Any supplementary introduction or hint may 

 most profitably and economically be written upon the blackboard. 



Most of the experiments given in this book cannot conveniently 

 be performed by one individual working alone. After some experi- 

 mentation it has been found most advantageous to divide the class 

 into sections not exceeding thirty students, and to subdivide these 

 sections into divisions of three students each. Each division is 

 assigned a table. The assistant demonstrator places the material 



