HISTOLOGY. 41 



body with the remains of the cell which gave it birth. Each of these 

 little bodies may be compared to a laboratory, which receives from the 

 surrounding matter the elements which it requires, and combines them so 

 as to produce a desired result. 



The various modifications and aggregations of these cells constitute the 

 varied forms of animal and vegetable tissues. 



DEVELOPMENT OF CELLS. 



A cell originates in a mass of soft or liquid matter, which is organizable 

 or capable of being organized. In other words, a liquid formed of a com- 

 bination of elements fitted to produce an organized structure. This sub- 

 stance is called "blastema." As an example, we may take the liquor 

 sanguinis or the blood, excluding its globules, which in a fully formed 

 animal is a universally diffused blastema. 



A minute point (see Fig. 2) arises in this blastema, which increases in 



size ; a transparent wall is seen to 

 s ' 2> * spring up like a watch-glass from one 



side of the granule, which swells up 

 more and more until the granule is seen 

 to exist in, and adhere to the side of the 

 cell wall. When thus formed, we have 

 the cell wall with its fluid contents, and the granule or nucleus, which 

 may by this time have developed several new granules or nucleoli in its 

 interior. 



MULTIPLICATION OF CELLS. 



Cells are multiplied in several modes : 



1st. By repetition, i. e., of the development from a blastema, as ex- 

 plained. 



2d. By the development of new nuclei and cells within the parent cell 

 wall (see fig. 3). 



Fig. 3.t Fig. 44 



3d. By the development of new cells from the parietes of pre-existing 

 ones., This is shown in fig. 4. 



TRANSFORMATION OF CELLS. 



1st. Cells may lose their fluid contents, and their walls collapsing until 

 they come in contact and adhere, they form simple, membranous, and 

 transparent discs. f 



* Development of cell from blastema. On the left is seen the corpuscle which he 

 comes the nucleus ; on the right the complete nucleated cell, 

 f Development of new cells within the parent cell, 

 i Development rf new cells from the outer wall of pre-existing cells. 

 4* 



