10 GENERAL PHYSIOLOGY 



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importance which many centuries later Harvey knew how to give 

 it, Galen himself practised vivisection upon pigs and monkeys. 



Along with general recognition of his immortal service, Galen 

 has often been reproached with the charge that he was not content 

 with collecting physiological facts, making observations and devis- 

 ing experiments, but that he felt strongly the necessity of arrang- 

 ing his collected material into a complete and comprehensive 

 system of physiology, in which he allowed hypothesis and philo- 

 sophical speculation a place that exact investigation ought to 

 have filled. Nothing can be more unjust than this reproach. If 

 Galen had been satisfied with ascertaining disconnected physio- 

 logical facts, physiology and with it all medicine would not have 

 been advanced one step farther than Aristotle had already brought 

 them. Galen's greatest importance lies in the union of scraps 

 of physiological knowledge into a coherent system. Isolated 

 observations obtain value only in connection with other facts, and 

 only a survey of the relations of facts makes possible further 

 systematic progress. It is only natural that, in this first attempt 

 to put together the material of physiological observation into a 

 coherent picture of the life of the human body, recourse must now 

 and then be had to hypothesis, even much bold hypothesis. The 

 single fault from which Galen's system suffers is not its binding 

 cement of philosophical speculation, but the peculiar dualism that 

 misled him, in accordance with which, in explaining vital 

 phenomena, he strove to give at the same time a place both to 

 the rigid idea of necessity, which sprang from his exact scientific 

 investigations, and to teleology, which was derived from the 

 Aristotelian philosophy. Nevertheless, in a just estimation of his 

 time, when Aristotelian ideas had already begun a universal sway 

 that was to last more than a thousand years, Galen can scarcely be 

 reproached for this, the less when it is recalled that the teleological 

 idea of a final purpose in all things appears here and there 

 in modern natural science even to-day, quite independent of 

 philosophy. 



Galen's system is based upon the doctrine of the spirits (pneuma). 

 The causes of all the vital phenomena of the human body, which 

 is composed of the four fundamental juices, viz. : the blood, the 

 phlegm, the yellow and the black gall, are the three different forms 

 of spirits, of which the animal spirits (irvevfjia ^V^LKOV) have their 

 seat in the brain and the nerves, the vital spirits (irvevfjua fari/cov) 

 in the heart, and the natural spirits (Trvev/jia (frvo-i/cov) in the liver. 

 These three forms, which must be regenerated continually by 

 the receipt of vital spirits from the air, are the agencies that 

 maintain the functions of the respective organs. The body 

 possesses many functions, but they may be arranged, according to 

 the forms of the spirits, into three classes, and each function is 

 carried on by a faculty (SiW/zt?) corresponding to its respective 



