OUK LIFE. 41 



researches into the organs of the body he never lost 

 sight of the question of their vital activity, their 

 functions ; and even in this direction he proceeded by 

 the same comparative method, taking for his principal 

 study the animals which approach nearest to man. 

 Whatever he learned from these he applied directly 

 to man. He recognised the value of physiological 

 experiment ; in his vivisection of apes, dogs, and 

 swine he made a number of interesting experiments. 

 Vivisection has been made the object of a violent 

 attack in recent years, not only by the ignorant and 

 narrow-minded, but by theological enemies of know- 

 ledge and by perfervid sentimentalists ; it is, how- 

 ever, one of the indispensable methods of research 

 into the nature of life, and has given us invaluable 

 information on the most important questions. This 

 was recognised by Galen 1700 years ago. 



Galen reduces all the different functions of the body 

 to three groups, which correspond to the three forms 

 of the pneuma, or vital spirit. The pneuma psyehicon 

 — the soul — which resides in the brain and nerves, 

 is the cause of thought, sensation, and will (volun- 

 tary movement) ; the pneuma zoticon — the heart — is 

 responsible for the beat of the heart, the pulse, and 

 the temperature ; the pneuma physicon, seated in the 

 liver, is the source of the so-called vegetative func- 

 tions, digestion and assimilation, growth and repro- 

 duction. He especially emphasized the renewal of 

 the blood in the lungs, and expressed a hope that we 

 should some day succeed in isolating the permanent 

 element in the atmosphere — the pneuma, as he calls 

 it — which is taken into the blood in respiration. 

 More than fifteen centuries elapsed before this pneuma 

 — oxygen — was discovered by Lavoisier. 



