86 BIOLOGY AND PHYSICAL SCIENCES 



cally determined determined as in definite 

 relation to the whole functional and structural 

 activities of the organism, and not merely 

 dependent on specific and one-sided conditions, 

 such as the abundance of oxygen in the in 

 spired air, or its freedom from carbon dioxide, 

 or some mechanical action of the nervous 

 system, unrelated to the central organic deter 

 mination. 



Misled by mechanistic conceptions of life, 

 various physiologists have, as a matter of fact, 

 put forward one-sided theories of this kind, 

 and they have invariably turned out to be 

 wrong. As an example we may take the 

 theory that owing to the structure of the 

 respiratory centre, and the properties of the 

 afferent nerves coming to it from the lungs, 

 breathing goes on, under ordinary conditions, 

 automatically and without reference to the 

 removal of carbon dioxide or intake of oxygen. 

 It was believed that as distention of the lungs 

 excites fibres in the vagus-nerve which inhibit 

 inspiration, and collapse of the lung correspond 

 ingly excites fibres which excite inspiration, 

 normal breathing is regulated by this mechan 

 ism, though the centre also responds to any 



