58 HISTOLOGY OF MEDICINAL PLANTS 
Yet all cells performing a given function will structurally re- 
semble each other. In the present work the nucleus and other 
parts of the living protoplast will not be considered, for the 
reason that these parts are not in a condition suitable for study, 
because most drugs come to market in a dried condition, a con- 
dition which eliminates the possibility of studying the proto- 
plast. The general structure of the cells forming the different 
tissues will first be considered, then their variation, as seen in 
different plants, and finally their functions. 
