2 GENERAL PHYSIOLOGY 



the purpose of helping to solve a problem that concerns a practical 

 or a theoretical need of life, and those that deal with chance or any 

 external circumstance for the purpose of seeing what, if anythmg, 

 will be the outcome. The former constitute true research, the 

 latter, pastime. One-sided specialisation considers none of the 

 great needs of mankind, and brings science finally to the unen- 

 viable standpoint of the famulus Wagner. 



It is absolutely essential to the advance of a science that in its 

 special researches it keep clearly in view its general aim, its great 

 problem ; investigation then becomes systematic. This is possible 

 only when the investigator possesses such a survey as is referred 

 to above. 



Such an outlook over aims, paths, and achievements, in place of 

 a mass of disconnected facts, is required, not by the individual in- 

 vestigator alone, but by every cultured man who would learn from 

 science what is of value for the practical or theoretical needs of 

 his life ; for science serves life, not life science. 



I. The Problem of Physiology 



The ancient Greeks associated with the word "<jivai,<s" the concep- 

 tion of all living nature, a significance that finds expression in its 

 purest form in the Homeric poems. Since that time the idea 

 expressed by the word has undergone many changes. The original 

 significance soon gave place to a more general one, and at the height 

 of Grecian culture the Ionic philosophers, the oldest natural 

 philosophers of Greece, were called " (^uo-t6A.o7ot," the conception of 

 </)uo-t9 being extended to all nature. Later, with the separation 

 of physics as an independent science in its present sense, the con- 

 ception became again narrow, but different from the orio-inal one, 

 being limited to non-living nature and thus possessing a significance 

 the exact opposite of the original one. 



If the word (/)vcrt9 be conceived in its proper original sense, the 

 term " Physiology " expresses fully the essence of the science to 

 which the term is now applied, and it is unnecessary to replace it 

 with the later word " Biology," with which at present very different 

 ideas are associated. 



Physiology is the science of the phenomena of living nature, and, 

 accordingly, its task is the investigation of life. 



In spite of the apparent simplicity of its task, the science has 

 already laboured for centuries upon this problem. A little con- 

 sideration will make its difficulties evident. It is only necessary to 

 attach ideas to the expressions " life " and " investigation," which 

 in this combination appear at first as empty words. 



We will consider first the subject-matter of physiology, namely 

 life. The untrained person associates usually with this word a 



