126 WHAT IS LIFE ? 



portant point to observe is : that although the mature 

 brain has almost an infinite number of cells to produce 

 the most complex thought, yet the human being is only 

 able to bring a few of these cells into operation at the 

 time. We think of only one thing at the time, and 

 perform one action at the time involving the power of 

 the will and this is our common experience. 1 It is 

 when external conditions require us to try to think of 

 more than one thing at the time we experience the 



the lungs, or the heart. Thus, a man may be instantly killed by 

 such an injury to a part of the brain which is called the medulla 

 oblongata ... as may be produced by hanging, or breaking the 

 neck." (" Lessons in Elementary Physiology," T. H. Huxley, LL.D., 

 F.R.S., 1895, p. 19.) 



" Destruction of the spinal bulb at once arrests the movements 

 of respiration ; and provided the bulb be left intact, destruction of 

 the brain does not abolish these movements. This of itself is enough 

 to show that the spinal bulb includes the chief respiratory centre, 

 even though it is not possible to define the centre anatomically as 

 this or that nucleus of grey matter." (" An Introduction to Human 

 Physiology," A. D. Waller, M.D., F.R.S., 1896, p. 148.) 



" The regulation of the vascular system is administered by the 

 central nervous system, viz. the medulla oblongata or spinal bulb, 

 and the spinal cord, from which the vascular and cardiac nerves take 

 origin, the particular parts from which they spring being spoken of 

 as their ' centres,' and comprising (1) the vagus centre in the bulb, 

 (2) the accelerator centre in the cord, (3) the principal vasomotor 

 centre in the bulb, (4) accessory vasomotor centres in the cord. The 

 mode of action of these centres has been experimentally examined by 

 observing, (a) the consequences of their destruction or direct stimula- 

 tion, (b) the consequences of stimulation of afferent nerves before and 

 after destruction of the bulb or cord." (Idem, p. 110.) 



1 " When our attention is brought to bear forcibly on a thing we 

 think for the moment of nothing else, and every one knows that if we 

 are absorbed by interesting reading others may talk around us while 

 we do not hear them." (" Alterations of Personality," Alfred Binet, 

 1896, p. 141.) 



