PART FIRST. 



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CHAPTER I. 



ORIGIN OF THE TISSUES. 



TISSUE is a phrase applied to an elementary part, or 

 structure of the body, and consists in a peculiar arrange- 

 ment of fibres. 



An Organ is composed of several Tissues. 



The Nucleated Cell, (fig. !_,) from observations 



Owith the microscope, first announced by Schwann 

 in 1838, is now generally received as the ele- 

 ^ mentary, or first form, in which animal matter is 

 developed, and from which, as the basis, all or- 



ganic structures, whether vegetable or animal, are formed. 

 This cell is described as a vesicle of delicate membrane, 

 containing a fluid, and a minute dark nucleus, called Cyto- 

 blast, or Cell-germ (from xutoj, cell,, and pKwtos, germ,) and 

 is surrounded by an amorphous substance, either solid or 

 fluid, called blastema or cytoblastema, from which the cell 

 itself springs. 



The Nucleus presents a round or oval shape, somewhat 

 flattened, its surface smooth or granular, of a yellowish 

 red, or without color, and having a diameter from the four- 

 thousandth to the two-thousandth part of a line. 



FIG. 1. Represents the Cell with its contained Nucleus, and the Nucleus 

 without any Cell. 



