132 THE MICROSCOPIST. 



gradually enlarges till at last the nucleus is seen only as a spot 

 on its wall. The whole is then called a nucleated cell, or ger- 

 minal cell. The fluid in which the granules are fir'st deposited 

 is called the cytoblastema. 



In the second method of development, each granule of the 

 nucleus has the power of developing a cell, so that the parent 

 cell becomes filled with one or more generations of new cells, 

 which may either disappear entirely, or by the rupture of the 

 original cells the contents may be scattered, and undergo an 

 independent development. 



Sometimes several nucleoli are seen within one nucleus, and 

 several nuclei within one cell. 



Each cell is an independent organ, living for itself, and by 

 itself, and depending upon nothing but a proper supply of nu- 

 triment, and of the appropriate stimuli for the continuance of 

 its growth and for the performance of its functions, until its 

 term of life is expired. 



The development of cells goes on at every period during the 

 life of the organism. They are found floating in immense 

 numbers in the blood, chyle, and lymph; and even in dis- 

 eased secretions, as pus. In the inflammatory process they 

 are produced in great quantities ; and the malignant growths, 

 such as cancer and fungus hcematodes, which infest the body, 

 are owing to the same agencies. In short, the nucleated cell is 

 the agent of most of the organic processes, both in the plant 

 and animal, from the dawn of their existence to their full 

 maturation and decline. 



The forms of cells are various (see Fig. 24) ; some being sphe- 

 roidal, others cubical, prismatic, polygonal, or cylindrical. 

 They are subject also to various transformations. Sometimes 

 a number of cylindrical cells are laid end to end, and by the 

 absorption of the transverse partitions form a continuous tube ; 

 as ia the sap vessels of plants, muscular and nervous fibre, &c., 



