PREFACE. 5 



in this position not because this is the simplest part of the subject 

 of physiology to understand, but because it is the easiest to provide 

 material for and therefore the best in which to permit of sufficient 

 practice, so that the student may become familiar with the methods 

 of physiological technique. The two following sections deal with 

 essential experiments illustrating the principles of the heart beat 

 and the circulation of the blood. In selecting experiments in the 

 last mentioned group the endeavour has been made to apply them, 

 as far as possible, to man. A certain number of experiments in 

 which other mammalian material is used is, however, essential in 

 order that the student may be in a position to appreciate the 

 significance of results which will later be demonstrated to him. 

 These demonstrations are described in the last sections of the 

 manual in sufficient detail, so that the various steps may be followed 

 by every student of the general course and the experiments may 

 be performed by small groups of more advanced students. 



In the experiments on the central nervous system the decere- 

 brate or spinal animal is extensively made use of, as recommended 

 by C. S. Sherrington whose work in this direction must be con- 

 sidered as the most important contribution that has recently been 

 made to the advancement of the teaching of practical physiology. 

 In the section on the special senses a relatively larger proportion of 

 theoretical matter is given, along with the directions for the experi- 

 ments, partly because the latter, being practically all subjective 

 in nature, cannot be performed unless the student understands fully 

 what he is looking for, and partly because most of them can, and 

 should be performed in the study rather than the laboratory. 



A great difficulty has always been felt by instructors in physi- 

 ology in attempting to supply simple experiments bearing on 

 the chemistry of respiration and yet there is no part of physiology 

 in which practical experience is more important, if the student is 

 to understand the principles of this difficult subject. A section of 

 the manual is devoted to experiments in which simplified and inex- 

 pensive apparatus for gas analysis is employed. 



Throughout the book, besides the directions for the experi- 

 ments, a brief statement is given of the theoretical matter which 

 bears on them. This is done to enable the student to appreciate 

 the object of the experiment and to guide him in the interpretation 



