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To some extent, also, axons pass through ganglia with which they make no connection. The neurons in the brain and spinal cord also lie side by side, but their arrangement is more complex than that in the nerves and ganglia. Ganglion. 2. Nerve. In the ganglion of A are end-to-end connections of different neurons; in the ganglion of B are the cell-bodies of di-axonic neurons.
And again only the higher layer of the neurons in the population sees its doings recorded in the annals of history; and yet whatever those leaders of action and thought and emotion may achieve is dependent upon and working on the actions of those millions of subcortical population neurons. The historical record has its unity through the interrelation of all parts of historical mankind.
Let us merely recall that a theory such as that according to which consciousness is attached to certain neurons, and is thrown off from their work like a phosphorescence, may be accepted by the scientist for the detail of analysis; it is a convenient mode of expression. But it is nothing else. In reality, a living being is a centre of action.
The bulb, because of certain special reflex-action pathways completed through it, is the portion of the central nervous system concerned in the control of respiration, circulation, and the secretion of liquids. *Work of the Sympathetic Ganglia and Nerves.*—The neurons which form these ganglia aid in controlling the vital processes, especially digestion and circulation.
If these are studied with reference to their origin, it will be seen that some of them result from the action of definite forms of stimuli upon the neurons terminating in sense organs; while the others, as a rule, arise from the action of indefinite stimuli upon neurons in parts of the body that do not possess sense organs.
For example, a single neuron passing out from the spinal cord may, by terminating in a sympathetic ganglion, stimulate a large number of neurons, each of which will in turn stimulate the cells of muscles or of glands. Because of this function, the sympathetic neurons are sometimes called distributing neurons.
From spoken language man has advanced to written language, so that the sight of the written or printed word also arouses in the mind the associated idea. *The Ear* is the sense organ which enables sound waves to so act upon afferent neurons as to excite impulses in them. The effect upon the mind which these impulses produce is known as the sensation of hearing.
*How External Stimuli act on Internal Organs.*—For stimulating the neurons not connected with the body surface we are dependent, so far as known, upon the nervous impulses. An impulse started by the external stimulus goes only so far as its neuron extends.
Insight into the real nature of the nervous system is obtained only through a study of its minute structural elements. These, instead of being called cells, as in the case of the other tissues, are called neurons. The use of this term, instead of the simpler one of nerve cell, is the result of recent advances in our knowledge of the nervous system.
Several of the steps required to make the conversion from man to superman had resulted in temporary insanity; the wild, swinging imbalances of glandular secretions seeking a new balance, the erratic misfirings of neurons as they attempted to adjust to higher nerve-impulse velocities, and the sheer fatigue engendered by cells which were acting too rapidly for a lagging excretory system, all had contributed to periods of greater or lesser mental abnormality.
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