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This rock is much fendillated, externally of a bluish-grey, covered with dendrites of manganese, and internally of leek and asparagus-green, crossed by small veins of asbestos. It contains no garnet or amphibole, but metalloid diallage disseminated in the mass.
At the foot of the Castillo de in Punta, near the Havannah, on shelves of cavernous rocks,* covered with verdant sea-weeds and living polypi, we find enormous masses of madrepores and other lithophyte corals set in the texture of those shelves. Is the change of colour produced by the waters owing to the manganese which we recognize by some dendrites?
*Side-by-side Connections.*—On separating the ganglia and nerves into their finest divisions, it is found that the nerves consist of axons, while the ganglia are made up mainly of cell-bodies and dendrites. But the axons, in order to connect with the cell-bodies, must terminate within the ganglion, so that they too form a part of it.
But I have long been convinced that neither can the absence of 'dendrites' be regarded as indicative of recent age, nor their presence as sufficient to establish the great antiquity of the objects upon which they occur. I have myself noticed upon paper, which could scarcely be more than a year old, dendritic deposits, which could not be distinguished from those on fossil bones.
Their protoplasm, like that of the cell-body, is more or less granular. The dendrites increase greatly the surface of the cell-body, to which they are related in function. The axon, or nerve fiber, is a long, slender extension from the cell-body, which connects with some organ or tissue.
On account of this property, an excitation, or disturbance, in any part of a neuron is conducted or carried to all the other parts. Thus a disturbance at the distant ends of the dendrites causes a movement toward the cell-body and, reaching the cell-body, the disturbance is passed through it into the axon. This movement through the neuron is called the nervous impulse.
Ramon y Cajal, on the other hand, believes that the neuroglia cells are contractile, and may expand so as to interpose their branches as insulating material between the synapses formed by the dendrites of the nerve cells. The difficulty of accepting these theories is that nobody can locate consciousness to any particular group of nerve cells.
When these "dendrites" touch, communication is established; when this contact is broken, it is non-existent. To apply the analogy. On the other side, a communicator would also stretch out these mental arms, feeling about for something to grasp and cling to, something capable of receiving and transmitting the messages he desired to send.
The dendrites serve two purposes: first, they extend the surface of the cell-body, thereby enabling it to absorb a greater amount of nourishment from the surrounding lymph; second, they act as receivers of stimuli from other neurons. The same impulse does not pass from one neuron to another. The special function of the axon is to transmit the impulse.
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