50 ON THE EDUCATIONAL VALUE ii 



hearing apparatus, unless you close it up and 

 thereby discover that you become deaf? 



It would really be much more true to say that 

 Phj^siology is the experimental science par excel- 

 lence of all sciences; that in which there is least 

 to be learnt by mere observation, and that which 

 affords the greatest field for the exercise of those 

 faculties which characterise the experimental phi- 

 losopher. I confess, if any one were to ask me 

 for a model application of the logic of experiment, 

 I should know no better work to put into his 

 liands than Bernard's late Researches on the 

 Functions of the Liver.* 



Xot to give this lecture a too controversial 

 tone, however, I must only advert to one more 

 doctrine, held by a thinker of our own age and 

 country, whose opinions are worthy of all respect. 

 It is, that the Biological sciences ditfer from all 

 others, inasmuch as in i]ic?n classification takes 

 place by type and not by definition.! 



It is said, in short, that a natural-history class 

 is not capable of being defined — that the class 



* NouvplJe Fonrfion (hi Foie cnvaidere rnmme orgnne 

 prodncfeur de mntiere sucree chez Vllomme et les Animaux, 

 par IM. riandc Bernard. 



]'■'■ Natural Groii])S cjiveii hy Typo, nnt ht/ Definiitnn. 

 .... The class is steadily fixed, thoucrh not precisely 

 limited; it is given, though not circumscribed; it is deter- 

 mined, not by a boundary-line without, but by a central 

 point within ; not by what it strictly excludes, but what it 

 eminently includes; by an example, not by a precept; in 

 short, instead of Definition we have a Tjipo for our director. 

 A type is an example of any class, for instance, a species of 



