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qualities. The stomach cells undertake digestion, the blood cells 
exchange of matter, the lung cells respiration, the liver cells the 
formation of bile. On the other hand, the muscle cells devote 
themselves exclusively to motion, the sensory cells to various 
‘perceptions ; the touch cells of the skin learn to comprehend vari- 
ations of pressure and of warmth; the hearing cells to distinguish 
waves of sound, the seeing cells those of light; but the most 
difficult and brilliant course is run by the nerve cells ; and among 
these again are the ingenious brain cells which in the bold race 
carry off the highest prize, and as sozd/-ce//s elevate themselves far 
above all the other kinds. 
This most significant division of labour of the cells—or, as the 
anatomist says, building up of tissues—is completed in the indi- 
vidual development of every animal and of every plant under our 
eyes within a few days. The development, however, which we see 
here going on so astonishingly fast under the microscope, is only a 
short repetition, brought about through hereditary transmission, of 
a long and slow historical process—a historical precedent which 
required many millions of years, and in which the division of 
labour of the cells (in the strictest sense of the word) was caused 
by accommodation to the various life-activities of the cells in the 
battle for existence. The cells behave therein even just as the 
well educated citizens of a well regulated civilised state. In reality, 
our own bodies, as those of all the higher animals, are such civilised 
cell-states. The so-called tissues of the body, those of the muscles, 
of the nerves, of the glands, of the bones, of the ligaments, answer 
to the various ranks or guilds of a state, or yet more accurately to 
the hereditary cas/es, as we meet with them in ancient Egypt, and 
still at the present day in India. The tissues are hereditary cell- 
castes in the civilised state—the many-celled organism. The 
organs also, which again are constituted of various tissues, are to be 
compared to the various offices and institutions in the state. At 
the top of all stands the mighty central government—the nerve- 
centre—the brain. The more elaborately developed the higher 
animal, the more strongly centralised the cell-monarchy, so much 
the more powerful is the ruling brain, and so much the more nobly 
Oe 
