THE CELL 57 



if the unscientific person wishes to obtain a 

 rough idea of what it is like he may imagine 

 a child's toy air-balloon filled with unboiled 

 white of egg. In the centre of this white of 

 egg let him suppose that there is floating a 

 small bladder as big as say a Tangerine 

 orange, and that inside this sphere are some 

 tangled skeins of tape floating in a further 

 mass of unboiled white of egg. He will then 

 have constructed a mental model of a general- 

 ised cell. The air-balloon will represent the 

 coll wall and the white of egg within the cell- 

 protoplasm or cytoplasm. The contained 

 sphere will represent the nucleus and the skeins 

 of tape the chromatin skeins which it con- Nucleus 

 tains. The nucleus is generally though not 

 at all times included in a nuclear membrane 

 which is to it what the cell-wall is to the cell. 

 Within this membrane is a reticulum or net- 

 work, a ground substance or nuclear sap and 

 alten one or more nucleoli. 



Of all these portions the most essential is the 

 reticulum which consists of two parts, a general 

 protoplasmic basis, or linin, which closely re- 

 sembles cytoplasm, and a second constituent, 

 known, from its faculty of staining deeply 

 with certain re-agents, as chromatin. There Chromatin 

 are some who maintain that the interstitial 

 protoplasm is the most important part of the 



