50 LIFE AND DEATH. 



vital spontaneity. It is the statement that, under 

 determined circumstances materially identical, the 

 same vital phenomena will be identically reproduced. 

 Comparative Method. Claude Bernard completed 

 this critical work by laying down the laws of experi- 

 ment on living beings. He commended as the rational 

 method of research the comparative method. This 

 should be, and is in fact, the daily instrument of all 

 those who work in physiology. It compels the 

 investigator in every research bearing on organized 

 beings to institute a series of tests, such that the 

 conditions which are unknown and impossible to 

 know may be regarded as identical from one test to 

 another ; and when we are certain that a single 

 condition is variable, it compels him to discover the 

 character of the condition we are dealing with, and 

 to learn to appreciate, and to measure its influence. 

 It is safe to say that the errors which are daily 

 committed in biological work have their cause in 

 some infraction of this golden rule. In physical 

 science the obligation to follow the comparative 

 method is much less felt. In most cases the witness 

 test 1 is useless. In physiology the witness test is 

 indispensable. 



1 In an article on the experimental method recently published 

 in the Dictionnaire de Physiologic, M. Ch. Richet writes as 

 follows: "We must therefore never cease to carry out com- 

 parative experiments. I do not hesitate to say that this 

 comparison is the basis of the experimental method." It is in 

 fact what was taught by Claude Bernard in maxim and by 

 example. It is no exaggeration to assert that nine-tenths of the 

 errors which take place in research work are imputable to some 

 breach of this method. When an investigator makes a mistake, 

 save in the case of material error, it is almost certainly due to the 

 fact that he has neglected to carry out one of the comparative 



