Spencer. — On Life. 113 



the slow motion of the amoeba, but which are evidently and certainly only 

 miziute masses of living protoplasm enclosed within an outer coating — in 

 fact, vegetable cells, just as the amoeba is an animal cell. 



The chemical composition of this protoplasm is very complex. It is a 

 combination of C, H., 0., and N., and often contains also S. and P. Its 

 precise composition has not been determined, but it is probably nearly the 

 same as that of the white of the egg — pure albumen, the formula of which 

 is:— C. H. N. 0. S. P. 



53-5 7 15-5 22 1-6 0-4 



Of these protoplasmic cells, which I have so far described merely as 

 separate individualities, all living animal and vegetable structures are com- 

 pounded. We can discover them in all the living tissues of the vegetable 

 kingdom — in the roots, leaves, flowers, and seeds of herbs, shrubs, and 

 trees ; and in the tissues and blood of animals, — in that of man himself. If 

 a drop of blood be drawn from one of our fingers and placed under the 

 microscope, we see a multitude of reddish corpuscles, flattened ou the two 

 sides, and which show a tendency to arrange themselves in lines, like strings 

 of beads. But amongst these is a much smaller number of larger sized 

 colourless cells (the so-called white corpuscles), which, if kept at a proper 

 temperature, and under appropriate conditions, exhibit the same phenomena 

 as the amoeba — move slowly from place to place, change their shapes, and 

 project and withdraw those finger-like processes which have acquired 

 the name of pseudopodia. In living vegetable cells we do not, under 

 the microscope, see the same elastic movements as in animal cells, 

 because the limiting membrane is generally formed of cellulose, which 

 does not admit of the protrusions and retractions seen in the amoeba 

 and the white blood corpuscles ; but we have abundant evidence that the 

 protoplasmic contents are in a state of perpetual mechanical motion. In 

 the sting of the common English stinging nettle, and in various fresh-water 

 Algae, under sufficient magnifying power, minute granules in the fluid cell-con- 

 tents may be seen circling round and round the interior of the cell, showing 

 that the structureless protoplasm is in a condition of unceasing movement. 

 One of the most beautiful specimens of this cyclosis with which I am 

 acquainted, is to be found in the Closterium lunula. This microscopic 

 plant, which is very common in the ditches and pools in this vicinity, 

 belongs to the Desmidiace^, a family of the confervoid or green Algae. The 

 whole plant consists of a single cell of an elongated form, somewhat lunate 

 shape, broader in the centre, and tapering towards each end to a rounded 

 extremity. The interior is occupied with chloropliyl, excepting at the 

 extremities, where are clear transparent spaces, and a very narrow channel 



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