THE CELL-BODY. 



59 



and similar function are grouped to form tissues, and tissues are 

 grouped to form organs. 



We shall now consider the structure of the cell. Every cell 

 consists of a cell-body and a nucleus. 



A. THE CELL-BODY. 



The body of the cell consists of a substance known as proto- 

 plasm or cytoplasm. This is not a substance having uniform 



Vacuoles. 



Chromatin network. 



Linin network. 

 Nuclear fluid. 



Nuclear membrane. 

 Cell-membrane. 



Exoplasm. 



Spongioplasm. 

 Hyaloplasm. 



Nucleolus. 

 Chromatin net-knot. 



Centrosome. 

 Centrosphere. 



Foreign inclosures. Metaplasm. 

 Fig. 10. Diagram of a cell. 



physical and chemical qualities, but a mixture of various organic 

 compounds concerning which knowledge is not as yet conclusive, 

 but which in general are proteid bodies or albumins in the widest 

 sense. 



In spite of the manifold differences in its composition, proto- 

 plasm exhibits certain general fundamental properties which are 

 always present wherever it is found. Ordinarily, protoplasm ex- 

 hibits certain structural characteristics. In it are observed two con- 

 stituents, threads or plates, which are straight or winding, which 

 branch, anastomose, or interlace, and which are generally arranged in 

 a regular framework, network, or reticulum. These threads probably 

 consist of or contain small particles arranged in rows, called cell- 

 microsomes (vid. van Beneden, 83 ; M. Heidenhain, 94; and others). 

 Benda, who has devoted much time to the study of certain proto- 

 plasmic structures, has found in these threads small granules or 



