62 PHARMACEUTICAL BOTANY 



PROTOPLASM AND ITS PROPERTIES 



Protoplasm, or living matter, is the more or less semi-fluid, viscid, 

 foamy, and granular substance in which life resides. It is the 

 " physical basis of life." 



The peculiar properties which distinguish protoplasm from non- 

 living matter are as follows: 



1 . Structure. Protoplasm invariably exhibits structure. No por- 

 tion of it, however small, has been found to be homogeneous. Each 

 advance in microscopical technique reveals new complexities. The 

 protoplasm of a single cell, far from being a single unit, must rather 

 be looked upon as a microcosm. 



2. Metabolism. Perhaps the most significant peculiarity of 

 living matter is found in its instability and the chemical changes 

 which continually go on within it. It is constantly wasting away, 

 and as constantly being built up. These losses and gains are not 

 upon the exterior surface, but throughout its mass. Its growth and 

 renewal are by intussusception, or the taking in of new particles, 

 and storing them between those already present. A bit of pro- 

 toplasm may retain its indentity while all the matter of which it is 

 composed is changed over and over. It is like a whirlpool or wave in 

 a river which remains the same while the water of which it is com- 

 posed changes continually. Metabolism has been aptly defined by 

 Huxley as the whirlpool character of the organism. 



3. Irritability. All living matter responds to stimulation. When 

 matter fails to be irritable or responsive to stimuli, we declare it to 

 be dead. The stimuli that excite reactions in living matter are of 

 two kinds, viz; intrinsic and extrinsic. 



Intrinsic stimuli are inherited stimuli. They determine that the 

 plant shall conform to a particular type, carry on certain activities, 

 pass through a definite life cycle, and detach a portion of its own 

 substance for the formation of new individuals of its kind. 



Extrinsic stimuli initiate, inhibit, accelerate or modify the effects 

 of intrinsic stimuli. They comprise agents of the external world 

 such as cold, heat, chemicals, food, water, light, oxygen, electricity, 

 gravity etc. 



The irritable reactions manifested by protoplasm and living things 

 to the effects of these external agents will now be considered briefly. 



