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Locate and give the approximate number of the sympathetic ganglia. Show how the two portions of the spinal nerves are formed—the one from the mon-axonic and the other from the di-axonic neurons. Enumerate the different agencies through which the brain and spinal cord are protected. What cranial nerves contain afferent fibers? What ones contain efferent fibers?
Compare the skeleton outline of the nervous system with the bony skeleton. Sketch outlines of mon-axonic and di-axonic neurons. Give two differences between the neurons and the other cells of the body. Describe the two general methods of connecting neurons in the body. What purpose is accomplished by each method? Name and locate the principal divisions of the nervous system.
Pieces of cord of different colors and lengths are knotted to represent mon-axonic and di-axonic neurons. These are then pinned or tacked to the board in such a manner as to represent the connections in the different kinds of nerve pathways. *Study of the "Knee Jerk" Reflex.*—A boy is seated on a chair with the legs crossed.
It was at one time described as a distinct nervous element, but later study has shown it to be an outgrowth from the cell-body. The mon-axonic neurons are so called from their having but a single axon. *Di-axonic Neurons.*—Neurons belonging to this class have each a well-defined cell-body and two axons, but no parts just like the dendrites of mon-axonic neurons.
Though the neurons in certain parts of the body differ greatly in form and size from those in other parts of the body, most of them may be included in one or the other of two classes, known as mon-axonic neurons and di-axonic neurons. The cell-body has in itself the form of a complete cell and was at one time so described.
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.
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