AIMS OF PHYSIOLOGY. 27 



the four typical organs of locomotion of the Vertebrata, such a 

 discovery would indeed be hailed with delight by the morpho- 

 logist.5 But the physiological problem would remain unsolved ; 

 it would merely be transferred from the Vertebrata as a class to 

 that group to which this hypothetical animal might belong. From 

 the most general point of view the purely physiological problem 

 is, to say the least, of just as much importance as the morpho- 

 logical. 



After this illustration we may set morphology wholly aside, 

 and pass on to a genei-al preliminary consideration of the sub- 

 ject of the present volume, i.e. the ' General Physiology of the 

 Animal Kingdom,' or, as I first named it, the Physiology of 

 Animal Organisms — a title by which I intended to convey a 

 certain ojiposition or contradistinction of the subject of which 

 it treats to the general conception of Animal or Human Phy- 

 siology. 



Everyone is aware that the science which is usually known 

 simply as Physiology endeavours almost exclusively to explain 

 the functions of diflferent organs, and is not unfrequently con- 

 fined within even narrower limits, in accordance with the 

 assertion of a well-known German physiologist, that this science 

 is useful only or principally in practical medicine, and must be 

 regarded as subservient to it. This familiar form of physiology 

 is merely the physiology of the organs ; its aim is to verify the 

 laws by which the organs of sense — such as the brain — the 

 muscles, stomach, heart, spinal cord, lungs, kidneys — in short, 

 each of the various organs — exercise their functions. I am, I 

 need not say, far from disputing the immense value of this 

 branch of study, or even from thinking that its results can ever 

 be disregarded by the zoologist. I nevertheless must maintain 

 that another field, as yet almost unworked, lies open to physio- 

 logical enquiry — nay, more, that organic physiology has not 

 afforded such assistance to zoology as it might have done if it 

 had been less exclusively forced into the service of practical 

 medicine. An immense number of questions bearing the 

 highest general scientific importance lie open to physiological 

 enquiry in the vast number of different species of animals ; but 

 they are never, or but rarely, answered or even worked out, for 



