120 WHAT IS LIFE? 



By these special telegraph wires the brain sees, the 

 brain smells, tastes, and hears. And below this base 

 of the brain, the brain ramifies principally via the 

 spinal cord embedded in the backbones, all over the 

 body, forming connections for feeling, moving, &c. 

 Thus we obtain the conception of our central nervous 

 system, our headquarters and field telegraph for the 

 army of cells of which the living human being is 

 composed. 1 



1 Mr. Laing has so clearly described the apparatus by which we 

 think and are brought in contact with the external world that we 

 append his description.- He says : " The mechanism by which corre- 

 spondence is kept up between the living individual and the surround- 

 ing universe is very simple in reality, as simple as that of an ordinary 

 electric circuit. In the most complex case, that of man, there are a 

 number of nerve-endings, or small lumps of protoplasm, embedded in 

 the tissues all over the body, or highly specialized and grouped 

 together in separate organs such as the eye and ear, from which a 

 nerve-fibre leads direct to the brain, or to the spinal cord and so up to 

 the brain. These nerve-endings receive the different vibrations by 

 which outward energy presents itself, which propagate a current or 

 succession of vibrations of nerve-energy along the nerve-fibre. This 

 nerve-fibre is a round thread of protoplasm covered by a white sheath 

 of fatty matter which insulates it like the wire of a submarine tele- 

 graph coated with gutta-percha. This nerve-wire leads up to a 

 nerve-centre, consisting of two corpuscles of protoplasm : the first or 

 sensory, a smaller one, which is connected by branches with the 

 second, a much larger one, called the motor, from which a much 

 larger nerve-fibre or wire proceeds, which terminates in a mass of 

 protoplasm firmly attached to a muscle. Thus, a sensation is pro- 

 pagated along the sensory nerve to the sensory nerve-centre, whence 

 it is transmitted to the motor-centre, which acts as an accumulator of 

 stored-up energy, a large flow of which is sent through the large 

 conductor of the motor-nerve to the muscle, which it causes to con- 

 tract and thus produces motion. It is thus that the simpler involun- 

 tary actions are produced by a process which is purely mechanical. In 

 the more complex cases, in which consciousness and will are involved, 



