METHODS OF PHYSIOLOGICAL RESEARCH 9 



evident that the problem of physiology, the explanation of vital 

 phenomena, had already begun more or less clearly to be recog- 

 nised. Hitherto, individual physiological facts had been observed, 

 and physiological questions had been discussed incidentally. But 

 now, the more clearly the problem of physiology began to be 

 formulated, the more the treatment of physiological questions 

 began to assume the character of scientific investigation. 



Aristotle (384-322 B.C.), the great polyhistor of antiquity, estab- 

 lished the preliminary conditions for this advance by accumulating 

 .a vast mass of material in the form of facts. The significance of 

 Aristotle's relation to physiology does not lie in explaining vital 

 phenomena very often his explanations are uncritical, and, more- 

 over, they do not appear prominent in his work but rather in 

 observing and recording a great number of physiological phenomena. 

 In the midst of this material by the side of striking and acute 

 researches, there occurs, as might have been expected, much 

 erroneous observation ; such, for example, is the origin of eels and 

 frogs from mud by spontaneous generation. Nevertheless, his 

 recorded observations form the basis of the new stage of develop- 

 ment into which physiology passed after Aristotle, and which is 

 characterised by the clear recognition of the physiological problem 

 and its vast importance in practical medicine. 



After Aristotle, by his systematising work, had laid a broad 

 empirical foundation for natural science, the doctrine of the 

 pneuma received a wider extension among the later pneumatic 

 physicians, especially through the efforts of Athenaeus and 

 Aretaeus (both about 50 A.D.). It is in the nature of this 

 doctrine, that it must endeavour to comprehend and explain the 

 phenomena of life from a single point of view ; and, accordingly, 

 we find now for the first time a clear, conscious recognition of the 

 physiological problem and a systematic comprehension of physio- 

 logical phenomena. The man who first clearly perceived the nature 

 and significance of physiology was Galen (131 about 200 A.D.). 

 Galen saw that practical medicine could not thrive unless it 

 were based upon a very detailed knowledge of the normal vital 

 phenomena of the human body. The investigation of the vital 

 functions of the body must be the first pre-requisite of an art of 

 healing. This practical aim was the first incentive to the develop- 

 ment of physiology, and controlled the science almost exclusively 

 until the eighteenth century. Galen was also the first to recognise 

 clearly the importance of a knowledge of the anatomy of the body 

 in an understanding of the functions of its parts, and laid great 

 value upon the dissection of animals ; he himself dissected 

 pigs and monkeys especially. Moreover, he perceived the im- 

 portance of animal experimentation in the investigation of physio- 

 logical phenomena ; and, although the experimental method did 

 not assume under him that exact form and that fundamental 



