THE STRUCTURAL BASIS OF THE BODY 



17 



strung, so to speak, on a fine network of material known as linin. 

 Besides the granules of chromatin, other masses are sometimes 

 found which stain in a different manner and are called nucleoli. The 

 material filling up the meshes of the network is the nuclear sap or 

 nucleoplasm. The cytoplasm, which varies greatly in extent in different 

 cells, varies also in its appearance, being sometimes homogeneous, 

 sometimes alveolar, sometimes granular in structure. In it can be 



Attraction-sphere enclosing two centrosomes 



Nucleus - 



( Plasmosome 



or true 

 nucleolus 



Chromatin- 

 network 



Linin-network 



Karyosome, 

 net-knot, or 

 chromatin- 

 micleolus 



Plastids lying in the 

 cytoplasm 



Vacuole 



Passive bodies (meta- 

 plasm or paraplasm) 

 suspended in the cy- 

 toplasmic meshwork 



FIG. 3. Diagram of a cell. Its basis consists of a meshwork containing numerous 

 minute granules (microsomes) and traversing a transparent ground-substance. 

 (WILSON.) 



often distinguished differentiated parts which may be regarded as 

 organs of the cell. Thus in the amoeba we have the contractile 

 vacuoles already mentioned. In the green parts of plants the cyto- 

 plasm contains green granules, the chloroplasts, whose special function 

 it is to assimilate carbon dioxide from the atmosphere, and by means 

 of the energy of the sun's rays to convert this into starch with the 

 evolution of oxygen. Other parts of the plant have similar granules, 

 the leucoplasts, whose office it is to build up sugar into starch, and it 

 is possible that other kinds of these ( plastids ' with special chemical 

 functions are present in the cytoplasm of many cells. In addition to 

 these cell organs, the cytoplasm may contain granules which represent 

 stages in the metabolism of the cell and are either food material which 

 is being assimilated or products of the disintegration of the protoplasm, 

 formed either for the service of the cell itself or, in the case of the multi- 



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