The Fine Structure of the Mammalian Brain
The brains of six mammals drawn on the same scale in Figure 1.1 illustrate the evolutionary development of the brain from the primitive marsupial up to man, where the cerebrum and cerebellum are dominant. But size alone does not account for the preeminent performance of the human brain. This organ, weighing about 1.5 kg, is the most highly organized and the most completely organized matter known in the universe. At our present level of understanding, the brains of higher mammals are not greatly inferior in microstructure and in most aspects of operational performance. The brains of elephants and whales are many times larger—up to five times for a whale—and even the brain of the dolphin is a little larger than the human brain. Yet there is something very special about the human brain. It has a performance in relationship to culture, to consciousness, to language, and to memory, that uniquely distinguishes it from even the most highly developed brains of other animals. That is a problem that we shall discuss in the last chapter. We shall see there that it is beyond our comprehension how these subtle properties of the conscious self came to be associated with a material structure, the human brain that owes its origin to the biological process of evolution. We can state with complete assurance that for each of us, our brain forms the material basis of our experiences and memories, our imaginations, our dreams.
KeywordsNerve Fiber Nerve Cell Golgi Apparatus Synaptic Vesicle Rough Endoplasmic Reticulum
Unable to display preview. Download preview PDF.