12 ANATOMY AND PHYSIOLOGY 



this piece. Calculate the average length of the 

 cells, and the number of cells in the longest 

 filament observed. Estimate the length of an 

 individual cell in terms of its diameter, and from 

 this calculate the diameter of the filament. 



(e) Using the low power and removing the cover- 

 glass, carefully cut a filament apart with the 

 scalpel, causing as little injury as possible. As 

 you do this observe the exposed end-walls of 

 the uninjured cells that now terminate the fila- 

 ment where it was broken apart. Describe and 

 try to account for what you see. Is there any 

 evidence of the existence of a force within the 

 cell? If so, in what direction does it act? 

 Make two outline drawings, showing the con- 

 ditions before and after cutting. 



(/) Make a diagram about 75 mm. long, illustrating 

 the outline of the three terminal cells of a fila- 

 ment, as seen in optical section. Omit all de- 

 tails of cell-structure. 

 2. The individual cell. 



(a) Center your attention on any one of these cells, 

 and identify the following organs of the cell : 



(1) A cell-wall, enclosing all other parts of the 

 cell. Is it transparent or not? Give a 

 reason for your answer. Note its relative 

 thickness. The wall is composed of cellu- 

 lose. Has each cell its own end -wall, or is 

 there a common end-wall for two adjacent 

 cells? 



(2) The substance enclosed by the cell-wall is 

 largely living matter, or matter in the living 

 state. It is called protoplasm. The unit 

 of protoplasm of each individual cell is 



