CHAPTER IV 



THE CELL 



Its Parts Protoplasm and its Characters Nucleus 

 Chromosomes Relations of Nucleus and Cell Proto- 

 plasm. 



IN 1651 William Harvey, the great English 

 naturalist and physician, in his work De Gene- 

 ratione Animalium, laid down the axiom Omne 

 vivum ex ovo. This generalisation has since 

 been shown to have lacked complete accuracy, 

 since certain living things propagate them- 

 selves by fission. But if we alter it to read 

 Omne vivum ex vivo we arrive at a statement 

 which is now generally accepted by the scien- 

 tific world, though it has been strenuously 

 opposed and is still contested by a few as will 

 be more fully described in the chapter dealing 

 with abiogenesis. Second only in importance 

 to this generalisation is that which Virchow 

 proclaimed in 1858, Omnis cellula ex cellula.* 



* The Cell-Theory was first enunciated by Theodor 

 Schwann, a German, but successively Professor at Louvain 

 and Liege (1810-1882), and the honour of being its father 

 must ever remain with him. Nor must his co-worker, 

 Schleiden, be forgotten, but the fact remains that Virchow 

 played a very great part in securing its universal recognition 

 by his pathological theories and his other writings. 



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